The DRBD driver

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>

17 files changed, 20363 insertions, 0 deletions

diff --git a/drivers/block/drbd/Kconfig b/drivers/block/drbd/Kconfig
new file mode 100644
index 00000000000..4e6f90f487c
--- /dev/null
+++ b/drivers/block/drbd/Kconfig
@@ -0,0 +1,82 @@
+#
+# DRBD device driver configuration
+#
+
+comment "DRBD disabled because PROC_FS, INET or CONNECTOR not selected"
+	depends on !PROC_FS || !INET || !CONNECTOR
+
+config BLK_DEV_DRBD
+	tristate "DRBD Distributed Replicated Block Device support"
+	depends on PROC_FS && INET && CONNECTOR
+	select LRU_CACHE
+	default n
+	help
+
+	  NOTE: In order to authenticate connections you have to select
+	  CRYPTO_HMAC and a hash function as well.
+
+	  DRBD is a shared-nothing, synchronously replicated block device. It
+	  is designed to serve as a building block for high availability
+	  clusters and in this context, is a "drop-in" replacement for shared
+	  storage. Simplistically, you could see it as a network RAID 1.
+
+	  Each minor device has a role, which can be 'primary' or 'secondary'.
+	  On the node with the primary device the application is supposed to
+	  run and to access the device (/dev/drbdX). Every write is sent to
+	  the local 'lower level block device' and, across the network, to the
+	  node with the device in 'secondary' state.  The secondary device
+	  simply writes the data to its lower level block device.
+
+	  DRBD can also be used in dual-Primary mode (device writable on both
+	  nodes), which means it can exhibit shared disk semantics in a
+	  shared-nothing cluster.  Needless to say, on top of dual-Primary
+	  DRBD utilizing a cluster file system is necessary to maintain for
+	  cache coherency.
+
+	  For automatic failover you need a cluster manager (e.g. heartbeat).
+	  See also: http://www.drbd.org/, http://www.linux-ha.org
+
+	  If unsure, say N.
+
+config DRBD_TRACE
+	tristate "DRBD tracing"
+	depends on BLK_DEV_DRBD
+	select TRACEPOINTS
+	default n
+	help
+
+	  Say Y here if you want to be able to trace various events in DRBD.
+
+	  If unsure, say N.
+
+config DRBD_FAULT_INJECTION
+	bool "DRBD fault injection"
+	depends on BLK_DEV_DRBD
+	help
+
+	  Say Y here if you want to simulate IO errors, in order to test DRBD's
+	  behavior.
+
+	  The actual simulation of IO errors is done by writing 3 values to
+	  /sys/module/drbd/parameters/
+
+	  enable_faults: bitmask of...
+	  1	meta data write
+	  2               read
+	  4	resync data write
+	  8	            read
+	  16	data write
+	  32	data read
+	  64	read ahead
+	  128	kmalloc of bitmap
+	  256	allocation of EE (epoch_entries)
+
+	  fault_devs: bitmask of minor numbers
+	  fault_rate: frequency in percent
+
+	  Example: Simulate data write errors on /dev/drbd0 with a probability of 5%.
+		echo 16 > /sys/module/drbd/parameters/enable_faults
+		echo 1 > /sys/module/drbd/parameters/fault_devs
+		echo 5 > /sys/module/drbd/parameters/fault_rate
+
+	  If unsure, say N.
diff --git a/drivers/block/drbd/Makefile b/drivers/block/drbd/Makefile
new file mode 100644
index 00000000000..7d86ef8a8b4
--- /dev/null
+++ b/drivers/block/drbd/Makefile
@@ -0,0 +1,8 @@
+drbd-y := drbd_bitmap.o drbd_proc.o
+drbd-y += drbd_worker.o drbd_receiver.o drbd_req.o drbd_actlog.o
+drbd-y += drbd_main.o drbd_strings.o drbd_nl.o
+
+drbd_trace-y := drbd_tracing.o
+
+obj-$(CONFIG_BLK_DEV_DRBD)     += drbd.o
+obj-$(CONFIG_DRBD_TRACE)       += drbd_trace.o
diff --git a/drivers/block/drbd/drbd_actlog.c b/drivers/block/drbd/drbd_actlog.c
new file mode 100644
index 00000000000..74b4835d310
--- /dev/null
+++ b/drivers/block/drbd/drbd_actlog.c
@@ -0,0 +1,1484 @@
+/*
+   drbd_actlog.c
+
+   This file is part of DRBD by Philipp Reisner and Lars Ellenberg.
+
+   Copyright (C) 2003-2008, LINBIT Information Technologies GmbH.
+   Copyright (C) 2003-2008, Philipp Reisner <philipp.reisner@linbit.com>.
+   Copyright (C) 2003-2008, Lars Ellenberg <lars.ellenberg@linbit.com>.
+
+   drbd is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 2, or (at your option)
+   any later version.
+
+   drbd is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with drbd; see the file COPYING.  If not, write to
+   the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
+
+ */
+
+#include <linux/slab.h>
+#include <linux/drbd.h>
+#include "drbd_int.h"
+#include "drbd_tracing.h"
+#include "drbd_wrappers.h"
+
+/* We maintain a trivial check sum in our on disk activity log.
+ * With that we can ensure correct operation even when the storage
+ * device might do a partial (last) sector write while loosing power.
+ */
+struct __packed al_transaction {
+	u32       magic;
+	u32       tr_number;
+	struct __packed {
+		u32 pos;
+		u32 extent; } updates[1 + AL_EXTENTS_PT];
+	u32       xor_sum;
+};
+
+struct update_odbm_work {
+	struct drbd_work w;
+	unsigned int enr;
+};
+
+struct update_al_work {
+	struct drbd_work w;
+	struct lc_element *al_ext;
+	struct completion event;
+	unsigned int enr;
+	/* if old_enr != LC_FREE, write corresponding bitmap sector, too */
+	unsigned int old_enr;
+};
+
+struct drbd_atodb_wait {
+	atomic_t           count;
+	struct completion  io_done;
+	struct drbd_conf   *mdev;
+	int                error;
+};
+
+
+int w_al_write_transaction(struct drbd_conf *, struct drbd_work *, int);
+
+/* The actual tracepoint needs to have constant number of known arguments...
+ */
+void trace_drbd_resync(struct drbd_conf *mdev, int level, const char *fmt, ...)
+{
+	va_list ap;
+
+	va_start(ap, fmt);
+	trace__drbd_resync(mdev, level, fmt, ap);
+	va_end(ap);
+}
+
+static int _drbd_md_sync_page_io(struct drbd_conf *mdev,
+				 struct drbd_backing_dev *bdev,
+				 struct page *page, sector_t sector,
+				 int rw, int size)
+{
+	struct bio *bio;
+	struct drbd_md_io md_io;
+	int ok;
+
+	md_io.mdev = mdev;
+	init_completion(&md_io.event);
+	md_io.error = 0;
+
+	if ((rw & WRITE) && !test_bit(MD_NO_BARRIER, &mdev->flags))
+		rw |= (1 << BIO_RW_BARRIER);
+	rw |= ((1<<BIO_RW_UNPLUG) | (1<<BIO_RW_SYNCIO));
+
+ retry:
+	bio = bio_alloc(GFP_NOIO, 1);
+	bio->bi_bdev = bdev->md_bdev;
+	bio->bi_sector = sector;
+	ok = (bio_add_page(bio, page, size, 0) == size);
+	if (!ok)
+		goto out;
+	bio->bi_private = &md_io;
+	bio->bi_end_io = drbd_md_io_complete;
+	bio->bi_rw = rw;
+
+	trace_drbd_bio(mdev, "Md", bio, 0, NULL);
+
+	if (FAULT_ACTIVE(mdev, (rw & WRITE) ? DRBD_FAULT_MD_WR : DRBD_FAULT_MD_RD))
+		bio_endio(bio, -EIO);
+	else
+		submit_bio(rw, bio);
+	wait_for_completion(&md_io.event);
+	ok = bio_flagged(bio, BIO_UPTODATE) && md_io.error == 0;
+
+	/* check for unsupported barrier op.
+	 * would rather check on EOPNOTSUPP, but that is not reliable.
+	 * don't try again for ANY return value != 0 */
+	if (unlikely(bio_rw_flagged(bio, BIO_RW_BARRIER) && !ok)) {
+		/* Try again with no barrier */
+		dev_warn(DEV, "Barriers not supported on meta data device - disabling\n");
+		set_bit(MD_NO_BARRIER, &mdev->flags);
+		rw &= ~(1 << BIO_RW_BARRIER);
+		bio_put(bio);
+		goto retry;
+	}
+ out:
+	bio_put(bio);
+	return ok;
+}
+
+int drbd_md_sync_page_io(struct drbd_conf *mdev, struct drbd_backing_dev *bdev,
+			 sector_t sector, int rw)
+{
+	int logical_block_size, mask, ok;
+	int offset = 0;
+	struct page *iop = mdev->md_io_page;
+
+	D_ASSERT(mutex_is_locked(&mdev->md_io_mutex));
+
+	BUG_ON(!bdev->md_bdev);
+
+	logical_block_size = bdev_logical_block_size(bdev->md_bdev);
+	if (logical_block_size == 0)
+		logical_block_size = MD_SECTOR_SIZE;
+
+	/* in case logical_block_size != 512 [ s390 only? ] */
+	if (logical_block_size != MD_SECTOR_SIZE) {
+		mask = (logical_block_size / MD_SECTOR_SIZE) - 1;
+		D_ASSERT(mask == 1 || mask == 3 || mask == 7);
+		D_ASSERT(logical_block_size == (mask+1) * MD_SECTOR_SIZE);
+		offset = sector & mask;
+		sector = sector & ~mask;
+		iop = mdev->md_io_tmpp;
+
+		if (rw & WRITE) {
+			/* these are GFP_KERNEL pages, pre-allocated
+			 * on device initialization */
+			void *p = page_address(mdev->md_io_page);
+			void *hp = page_address(mdev->md_io_tmpp);
+
+			ok = _drbd_md_sync_page_io(mdev, bdev, iop, sector,
+					READ, logical_block_size);
+
+			if (unlikely(!ok)) {
+				dev_err(DEV, "drbd_md_sync_page_io(,%llus,"
+				    "READ [logical_block_size!=512]) failed!\n",
+				    (unsigned long long)sector);
+				return 0;
+			}
+
+			memcpy(hp + offset*MD_SECTOR_SIZE, p, MD_SECTOR_SIZE);
+		}
+	}
+
+	if (sector < drbd_md_first_sector(bdev) ||
+	    sector > drbd_md_last_sector(bdev))
+		dev_alert(DEV, "%s [%d]:%s(,%llus,%s) out of range md access!\n",
+		     current->comm, current->pid, __func__,
+		     (unsigned long long)sector, (rw & WRITE) ? "WRITE" : "READ");
+
+	ok = _drbd_md_sync_page_io(mdev, bdev, iop, sector, rw, logical_block_size);
+	if (unlikely(!ok)) {
+		dev_err(DEV, "drbd_md_sync_page_io(,%llus,%s) failed!\n",
+		    (unsigned long long)sector, (rw & WRITE) ? "WRITE" : "READ");
+		return 0;
+	}
+
+	if (logical_block_size != MD_SECTOR_SIZE && !(rw & WRITE)) {
+		void *p = page_address(mdev->md_io_page);
+		void *hp = page_address(mdev->md_io_tmpp);
+
+		memcpy(p, hp + offset*MD_SECTOR_SIZE, MD_SECTOR_SIZE);
+	}
+
+	return ok;
+}
+
+static struct lc_element *_al_get(struct drbd_conf *mdev, unsigned int enr)
+{
+	struct lc_element *al_ext;
+	struct lc_element *tmp;
+	unsigned long     al_flags = 0;
+
+	spin_lock_irq(&mdev->al_lock);
+	tmp = lc_find(mdev->resync, enr/AL_EXT_PER_BM_SECT);
+	if (unlikely(tmp != NULL)) {
+		struct bm_extent  *bm_ext = lc_entry(tmp, struct bm_extent, lce);
+		if (test_bit(BME_NO_WRITES, &bm_ext->flags)) {
+			spin_unlock_irq(&mdev->al_lock);
+			return NULL;
+		}
+	}
+	al_ext   = lc_get(mdev->act_log, enr);
+	al_flags = mdev->act_log->flags;
+	spin_unlock_irq(&mdev->al_lock);
+
+	/*
+	if (!al_ext) {
+		if (al_flags & LC_STARVING)
+			dev_warn(DEV, "Have to wait for LRU element (AL too small?)\n");
+		if (al_flags & LC_DIRTY)
+			dev_warn(DEV, "Ongoing AL update (AL device too slow?)\n");
+	}
+	*/
+
+	return al_ext;
+}
+
+void drbd_al_begin_io(struct drbd_conf *mdev, sector_t sector)
+{
+	unsigned int enr = (sector >> (AL_EXTENT_SHIFT-9));
+	struct lc_element *al_ext;
+	struct update_al_work al_work;
+
+	D_ASSERT(atomic_read(&mdev->local_cnt) > 0);
+
+	trace_drbd_actlog(mdev, sector, "al_begin_io");
+
+	wait_event(mdev->al_wait, (al_ext = _al_get(mdev, enr)));
+
+	if (al_ext->lc_number != enr) {
+		/* drbd_al_write_transaction(mdev,al_ext,enr);
+		 * recurses into generic_make_request(), which
+		 * disallows recursion, bios being serialized on the
+		 * current->bio_tail list now.
+		 * we have to delegate updates to the activity log
+		 * to the worker thread. */
+		init_completion(&al_work.event);
+		al_work.al_ext = al_ext;
+		al_work.enr = enr;
+		al_work.old_enr = al_ext->lc_number;
+		al_work.w.cb = w_al_write_transaction;
+		drbd_queue_work_front(&mdev->data.work, &al_work.w);
+		wait_for_completion(&al_work.event);
+
+		mdev->al_writ_cnt++;
+
+		spin_lock_irq(&mdev->al_lock);
+		lc_changed(mdev->act_log, al_ext);
+		spin_unlock_irq(&mdev->al_lock);
+		wake_up(&mdev->al_wait);
+	}
+}
+
+void drbd_al_complete_io(struct drbd_conf *mdev, sector_t sector)
+{
+	unsigned int enr = (sector >> (AL_EXTENT_SHIFT-9));
+	struct lc_element *extent;
+	unsigned long flags;
+
+	trace_drbd_actlog(mdev, sector, "al_complete_io");
+
+	spin_lock_irqsave(&mdev->al_lock, flags);
+
+	extent = lc_find(mdev->act_log, enr);
+
+	if (!extent) {
+		spin_unlock_irqrestore(&mdev->al_lock, flags);
+		dev_err(DEV, "al_complete_io() called on inactive extent %u\n", enr);
+		return;
+	}
+
+	if (lc_put(mdev->act_log, extent) == 0)
+		wake_up(&mdev->al_wait);
+
+	spin_unlock_irqrestore(&mdev->al_lock, flags);
+}
+
+int
+w_al_write_transaction(struct drbd_conf *mdev, struct drbd_work *w, int unused)
+{
+	struct update_al_work *aw = container_of(w, struct update_al_work, w);
+	struct lc_element *updated = aw->al_ext;
+	const unsigned int new_enr = aw->enr;
+	const unsigned int evicted = aw->old_enr;
+	struct al_transaction *buffer;
+	sector_t sector;
+	int i, n, mx;
+	unsigned int extent_nr;
+	u32 xor_sum = 0;
+
+	if (!get_ldev(mdev)) {
+		dev_err(DEV, "get_ldev() failed in w_al_write_transaction\n");
+		complete(&((struct update_al_work *)w)->event);
+		return 1;
+	}
+	/* do we have to do a bitmap write, first?
+	 * TODO reduce maximum latency:
+	 * submit both bios, then wait for both,
+	 * instead of doing two synchronous sector writes. */
+	if (mdev->state.conn < C_CONNECTED && evicted != LC_FREE)
+		drbd_bm_write_sect(mdev, evicted/AL_EXT_PER_BM_SECT);
+
+	mutex_lock(&mdev->md_io_mutex); /* protects md_io_page, al_tr_cycle, ... */
+	buffer = (struct al_transaction *)page_address(mdev->md_io_page);
+
+	buffer->magic = __constant_cpu_to_be32(DRBD_MAGIC);
+	buffer->tr_number = cpu_to_be32(mdev->al_tr_number);
+
+	n = lc_index_of(mdev->act_log, updated);
+
+	buffer->updates[0].pos = cpu_to_be32(n);
+	buffer->updates[0].extent = cpu_to_be32(new_enr);
+
+	xor_sum ^= new_enr;
+
+	mx = min_t(int, AL_EXTENTS_PT,
+		   mdev->act_log->nr_elements - mdev->al_tr_cycle);
+	for (i = 0; i < mx; i++) {
+		unsigned idx = mdev->al_tr_cycle + i;
+		extent_nr = lc_element_by_index(mdev->act_log, idx)->lc_number;
+		buffer->updates[i+1].pos = cpu_to_be32(idx);
+		buffer->updates[i+1].extent = cpu_to_be32(extent_nr);
+		xor_sum ^= extent_nr;
+	}
+	for (; i < AL_EXTENTS_PT; i++) {
+		buffer->updates[i+1].pos = __constant_cpu_to_be32(-1);
+		buffer->updates[i+1].extent = __constant_cpu_to_be32(LC_FREE);
+		xor_sum ^= LC_FREE;
+	}
+	mdev->al_tr_cycle += AL_EXTENTS_PT;
+	if (mdev->al_tr_cycle >= mdev->act_log->nr_elements)
+		mdev->al_tr_cycle = 0;
+
+	buffer->xor_sum = cpu_to_be32(xor_sum);
+
+	sector =  mdev->ldev->md.md_offset
+		+ mdev->ldev->md.al_offset + mdev->al_tr_pos;
+
+	if (!drbd_md_sync_page_io(mdev, mdev->ldev, sector, WRITE))
+		drbd_chk_io_error(mdev, 1, TRUE);
+
+	if (++mdev->al_tr_pos >
+	    div_ceil(mdev->act_log->nr_elements, AL_EXTENTS_PT))
+		mdev->al_tr_pos = 0;
+
+	D_ASSERT(mdev->al_tr_pos < MD_AL_MAX_SIZE);
+	mdev->al_tr_number++;
+
+	mutex_unlock(&mdev->md_io_mutex);
+
+	complete(&((struct update_al_work *)w)->event);
+	put_ldev(mdev);
+
+	return 1;
+}
+
+/**
+ * drbd_al_read_tr() - Read a single transaction from the on disk activity log
+ * @mdev:	DRBD device.
+ * @bdev:	Block device to read form.
+ * @b:		pointer to an al_transaction.
+ * @index:	On disk slot of the transaction to read.
+ *
+ * Returns -1 on IO error, 0 on checksum error and 1 upon success.
+ */
+static int drbd_al_read_tr(struct drbd_conf *mdev,
+			   struct drbd_backing_dev *bdev,
+			   struct al_transaction *b,
+			   int index)
+{
+	sector_t sector;
+	int rv, i;
+	u32 xor_sum = 0;
+
+	sector = bdev->md.md_offset + bdev->md.al_offset + index;
+
+	/* Dont process error normally,
+	 * as this is done before disk is attached! */
+	if (!drbd_md_sync_page_io(mdev, bdev, sector, READ))
+		return -1;
+
+	rv = (be32_to_cpu(b->magic) == DRBD_MAGIC);
+
+	for (i = 0; i < AL_EXTENTS_PT + 1; i++)
+		xor_sum ^= be32_to_cpu(b->updates[i].extent);
+	rv &= (xor_sum == be32_to_cpu(b->xor_sum));
+
+	return rv;
+}
+
+/**
+ * drbd_al_read_log() - Restores the activity log from its on disk representation.
+ * @mdev:	DRBD device.
+ * @bdev:	Block device to read form.
+ *
+ * Returns 1 on success, returns 0 when reading the log failed due to IO errors.
+ */
+int drbd_al_read_log(struct drbd_conf *mdev, struct drbd_backing_dev *bdev)
+{
+	struct al_transaction *buffer;
+	int i;
+	int rv;
+	int mx;
+	int active_extents = 0;
+	int transactions = 0;
+	int found_valid = 0;
+	int from = 0;
+	int to = 0;
+	u32 from_tnr = 0;
+	u32 to_tnr = 0;
+	u32 cnr;
+
+	mx = div_ceil(mdev->act_log->nr_elements, AL_EXTENTS_PT);
+
+	/* lock out all other meta data io for now,
+	 * and make sure the page is mapped.
+	 */
+	mutex_lock(&mdev->md_io_mutex);
+	buffer = page_address(mdev->md_io_page);
+
+	/* Find the valid transaction in the log */
+	for (i = 0; i <= mx; i++) {
+		rv = drbd_al_read_tr(mdev, bdev, buffer, i);
+		if (rv == 0)
+			continue;
+		if (rv == -1) {
+			mutex_unlock(&mdev->md_io_mutex);
+			return 0;
+		}
+		cnr = be32_to_cpu(buffer->tr_number);
+
+		if (++found_valid == 1) {
+			from = i;
+			to = i;
+			from_tnr = cnr;
+			to_tnr = cnr;
+			continue;
+		}
+		if ((int)cnr - (int)from_tnr < 0) {
+			D_ASSERT(from_tnr - cnr + i - from == mx+1);
+			from = i;
+			from_tnr = cnr;
+		}
+		if ((int)cnr - (int)to_tnr > 0) {
+			D_ASSERT(cnr - to_tnr == i - to);
+			to = i;
+			to_tnr = cnr;
+		}
+	}
+
+	if (!found_valid) {
+		dev_warn(DEV, "No usable activity log found.\n");
+		mutex_unlock(&mdev->md_io_mutex);
+		return 1;
+	}
+
+	/* Read the valid transactions.
+	 * dev_info(DEV, "Reading from %d to %d.\n",from,to); */
+	i = from;
+	while (1) {
+		int j, pos;
+		unsigned int extent_nr;
+		unsigned int trn;
+
+		rv = drbd_al_read_tr(mdev, bdev, buffer, i);
+		ERR_IF(rv == 0) goto cancel;
+		if (rv == -1) {
+			mutex_unlock(&mdev->md_io_mutex);
+			return 0;
+		}
+
+		trn = be32_to_cpu(buffer->tr_number);
+
+		spin_lock_irq(&mdev->al_lock);
+
+		/* This loop runs backwards because in the cyclic
+		   elements there might be an old version of the
+		   updated element (in slot 0). So the element in slot 0
+		   can overwrite old versions. */
+		for (j = AL_EXTENTS_PT; j >= 0; j--) {
+			pos = be32_to_cpu(buffer->updates[j].pos);
+			extent_nr = be32_to_cpu(buffer->updates[j].extent);
+
+			if (extent_nr == LC_FREE)
+				continue;
+
+			lc_set(mdev->act_log, extent_nr, pos);
+			active_extents++;
+		}
+		spin_unlock_irq(&mdev->al_lock);
+
+		transactions++;
+
+cancel:
+		if (i == to)
+			break;
+		i++;
+		if (i > mx)
+			i = 0;
+	}
+
+	mdev->al_tr_number = to_tnr+1;
+	mdev->al_tr_pos = to;
+	if (++mdev->al_tr_pos >
+	    div_ceil(mdev->act_log->nr_elements, AL_EXTENTS_PT))
+		mdev->al_tr_pos = 0;
+
+	/* ok, we are done with it */
+	mutex_unlock(&mdev->md_io_mutex);
+
+	dev_info(DEV, "Found %d transactions (%d active extents) in activity log.\n",
+	     transactions, active_extents);
+
+	return 1;
+}
+
+static void atodb_endio(struct bio *bio, int error)
+{
+	struct drbd_atodb_wait *wc = bio->bi_private;
+	struct drbd_conf *mdev = wc->mdev;
+	struct page *page;
+	int uptodate = bio_flagged(bio, BIO_UPTODATE);
+
+	/* strange behavior of some lower level drivers...
+	 * fail the request by clearing the uptodate flag,
+	 * but do not return any error?! */
+	if (!error && !uptodate)
+		error = -EIO;
+
+	drbd_chk_io_error(mdev, error, TRUE);
+	if (error && wc->error == 0)
+		wc->error = error;
+
+	if (atomic_dec_and_test(&wc->count))
+		complete(&wc->io_done);
+
+	page = bio->bi_io_vec[0].bv_page;
+	put_page(page);
+	bio_put(bio);
+	mdev->bm_writ_cnt++;
+	put_ldev(mdev);
+}
+
+#define S2W(s)	((s)<<(BM_EXT_SHIFT-BM_BLOCK_SHIFT-LN2_BPL))
+/* activity log to on disk bitmap -- prepare bio unless that sector
+ * is already covered by previously prepared bios */
+static int atodb_prepare_unless_covered(struct drbd_conf *mdev,
+					struct bio **bios,
+					unsigned int enr,
+					struct drbd_atodb_wait *wc) __must_hold(local)
+{
+	struct bio *bio;
+	struct page *page;
+	sector_t on_disk_sector = enr + mdev->ldev->md.md_offset
+				      + mdev->ldev->md.bm_offset;
+	unsigned int page_offset = PAGE_SIZE;
+	int offset;
+	int i = 0;
+	int err = -ENOMEM;
+
+	/* Check if that enr is already covered by an already created bio.
+	 * Caution, bios[] is not NULL terminated,
+	 * but only initialized to all NULL.
+	 * For completely scattered activity log,
+	 * the last invocation iterates over all bios,
+	 * and finds the last NULL entry.
+	 */
+	while ((bio = bios[i])) {
+		if (bio->bi_sector == on_disk_sector)
+			return 0;
+		i++;
+	}
+	/* bios[i] == NULL, the next not yet used slot */
+
+	/* GFP_KERNEL, we are not in the write-out path */
+	bio = bio_alloc(GFP_KERNEL, 1);
+	if (bio == NULL)
+		return -ENOMEM;
+
+	if (i > 0) {
+		const struct bio_vec *prev_bv = bios[i-1]->bi_io_vec;
+		page_offset = prev_bv->bv_offset + prev_bv->bv_len;
+		page = prev_bv->bv_page;
+	}
+	if (page_offset == PAGE_SIZE) {
+		page = alloc_page(__GFP_HIGHMEM);
+		if (page == NULL)
+			goto out_bio_put;
+		page_offset = 0;
+	} else {
+		get_page(page);
+	}
+
+	offset = S2W(enr);
+	drbd_bm_get_lel(mdev, offset,
+			min_t(size_t, S2W(1), drbd_bm_words(mdev) - offset),
+			kmap(page) + page_offset);
+	kunmap(page);
+
+	bio->bi_private = wc;
+	bio->bi_end_io = atodb_endio;
+	bio->bi_bdev = mdev->ldev->md_bdev;
+	bio->bi_sector = on_disk_sector;
+
+	if (bio_add_page(bio, page, MD_SECTOR_SIZE, page_offset) != MD_SECTOR_SIZE)
+		goto out_put_page;
+
+	atomic_inc(&wc->count);
+	/* we already know that we may do this...
+	 * get_ldev_if_state(mdev,D_ATTACHING);
+	 * just get the extra reference, so that the local_cnt reflects
+	 * the number of pending IO requests DRBD at its backing device.
+	 */
+	atomic_inc(&mdev->local_cnt);
+
+	bios[i] = bio;
+
+	return 0;
+
+out_put_page:
+	err = -EINVAL;
+	put_page(page);
+out_bio_put:
+	bio_put(bio);
+	return err;
+}
+
+/**
+ * drbd_al_to_on_disk_bm() -  * Writes bitmap parts covered by active AL extents
+ * @mdev:	DRBD device.
+ *
+ * Called when we detach (unconfigure) local storage,
+ * or when we go from R_PRIMARY to R_SECONDARY role.
+ */
+void drbd_al_to_on_disk_bm(struct drbd_conf *mdev)
+{
+	int i, nr_elements;
+	unsigned int enr;
+	struct bio **bios;
+	struct drbd_atodb_wait wc;
+
+	ERR_IF (!get_ldev_if_state(mdev, D_ATTACHING))
+		return; /* sorry, I don't have any act_log etc... */
+
+	wait_event(mdev->al_wait, lc_try_lock(mdev->act_log));
+
+	nr_elements = mdev->act_log->nr_elements;
+
+	/* GFP_KERNEL, we are not in anyone's write-out path */
+	bios = kzalloc(sizeof(struct bio *) * nr_elements, GFP_KERNEL);
+	if (!bios)
+		goto submit_one_by_one;
+
+	atomic_set(&wc.count, 0);
+	init_completion(&wc.io_done);
+	wc.mdev = mdev;
+	wc.error = 0;
+
+	for (i = 0; i < nr_elements; i++) {
+		enr = lc_element_by_index(mdev->act_log, i)->lc_number;
+		if (enr == LC_FREE)
+			continue;
+		/* next statement also does atomic_inc wc.count and local_cnt */
+		if (atodb_prepare_unless_covered(mdev, bios,
+						enr/AL_EXT_PER_BM_SECT,
+						&wc))
+			goto free_bios_submit_one_by_one;
+	}
+
+	/* unnecessary optimization? */
+	lc_unlock(mdev->act_log);
+	wake_up(&mdev->al_wait);
+
+	/* all prepared, submit them */
+	for (i = 0; i < nr_elements; i++) {
+		if (bios[i] == NULL)
+			break;
+		if (FAULT_ACTIVE(mdev, DRBD_FAULT_MD_WR)) {
+			bios[i]->bi_rw = WRITE;
+			bio_endio(bios[i], -EIO);
+		} else {
+			submit_bio(WRITE, bios[i]);
+		}
+	}
+
+	drbd_blk_run_queue(bdev_get_queue(mdev->ldev->md_bdev));
+
+	/* always (try to) flush bitmap to stable storage */
+	drbd_md_flush(mdev);
+
+	/* In case we did not submit a single IO do not wait for
+	 * them to complete. ( Because we would wait forever here. )
+	 *
+	 * In case we had IOs and they are already complete, there
+	 * is not point in waiting anyways.
+	 * Therefore this if () ... */
+	if (atomic_read(&wc.count))
+		wait_for_completion(&wc.io_done);
+
+	put_ldev(mdev);
+
+	kfree(bios);
+	return;
+
+ free_bios_submit_one_by_one:
+	/* free everything by calling the endio callback directly. */
+	for (i = 0; i < nr_elements && bios[i]; i++)
+		bio_endio(bios[i], 0);
+
+	kfree(bios);
+
+ submit_one_by_one:
+	dev_warn(DEV, "Using the slow drbd_al_to_on_disk_bm()\n");
+
+	for (i = 0; i < mdev->act_log->nr_elements; i++) {
+		enr = lc_element_by_index(mdev->act_log, i)->lc_number;
+		if (enr == LC_FREE)
+			continue;
+		/* Really slow: if we have al-extents 16..19 active,
+		 * sector 4 will be written four times! Synchronous! */
+		drbd_bm_write_sect(mdev, enr/AL_EXT_PER_BM_SECT);
+	}
+
+	lc_unlock(mdev->act_log);
+	wake_up(&mdev->al_wait);
+	put_ldev(mdev);
+}
+
+/**
+ * drbd_al_apply_to_bm() - Sets the bitmap to diry(1) where covered ba active AL extents
+ * @mdev:	DRBD device.
+ */
+void drbd_al_apply_to_bm(struct drbd_conf *mdev)
+{
+	unsigned int enr;
+	unsigned long add = 0;
+	char ppb[10];
+	int i;
+
+	wait_event(mdev->al_wait, lc_try_lock(mdev->act_log));
+
+	for (i = 0; i < mdev->act_log->nr_elements; i++) {
+		enr = lc_element_by_index(mdev->act_log, i)->lc_number;
+		if (enr == LC_FREE)
+			continue;
+		add += drbd_bm_ALe_set_all(mdev, enr);
+	}
+
+	lc_unlock(mdev->act_log);
+	wake_up(&mdev->al_wait);
+
+	dev_info(DEV, "Marked additional %s as out-of-sync based on AL.\n",
+	     ppsize(ppb, Bit2KB(add)));
+}
+
+static int _try_lc_del(struct drbd_conf *mdev, struct lc_element *al_ext)
+{
+	int rv;
+
+	spin_lock_irq(&mdev->al_lock);
+	rv = (al_ext->refcnt == 0);
+	if (likely(rv))
+		lc_del(mdev->act_log, al_ext);
+	spin_unlock_irq(&mdev->al_lock);
+
+	return rv;
+}
+
+/**
+ * drbd_al_shrink() - Removes all active extents form the activity log
+ * @mdev:	DRBD device.
+ *
+ * Removes all active extents form the activity log, waiting until
+ * the reference count of each entry dropped to 0 first, of course.
+ *
+ * You need to lock mdev->act_log with lc_try_lock() / lc_unlock()
+ */
+void drbd_al_shrink(struct drbd_conf *mdev)
+{
+	struct lc_element *al_ext;
+	int i;
+
+	D_ASSERT(test_bit(__LC_DIRTY, &mdev->act_log->flags));
+
+	for (i = 0; i < mdev->act_log->nr_elements; i++) {
+		al_ext = lc_element_by_index(mdev->act_log, i);
+		if (al_ext->lc_number == LC_FREE)
+			continue;
+		wait_event(mdev->al_wait, _try_lc_del(mdev, al_ext));
+	}
+
+	wake_up(&mdev->al_wait);
+}
+
+static int w_update_odbm(struct drbd_conf *mdev, struct drbd_work *w, int unused)
+{
+	struct update_odbm_work *udw = container_of(w, struct update_odbm_work, w);
+
+	if (!get_ldev(mdev)) {
+		if (__ratelimit(&drbd_ratelimit_state))
+			dev_warn(DEV, "Can not update on disk bitmap, local IO disabled.\n");
+		kfree(udw);
+		return 1;
+	}
+
+	drbd_bm_write_sect(mdev, udw->enr);
+	put_ldev(mdev);
+
+	kfree(udw);
+
+	if (drbd_bm_total_weight(mdev) <= mdev->rs_failed) {
+		switch (mdev->state.conn) {
+		case C_SYNC_SOURCE:  case C_SYNC_TARGET:
+		case C_PAUSED_SYNC_S: case C_PAUSED_SYNC_T:
+			drbd_resync_finished(mdev);
+		default:
+			/* nothing to do */
+			break;
+		}
+	}
+	drbd_bcast_sync_progress(mdev);
+
+	return 1;
+}
+
+
+/* ATTENTION. The AL's extents are 4MB each, while the extents in the
+ * resync LRU-cache are 16MB each.
+ * The caller of this function has to hold an get_ldev() reference.
+ *
+ * TODO will be obsoleted once we have a caching lru of the on disk bitmap
+ */
+static void drbd_try_clear_on_disk_bm(struct drbd_conf *mdev, sector_t sector,
+				      int count, int success)
+{
+	struct lc_element *e;
+	struct update_odbm_work *udw;
+
+	unsigned int enr;
+
+	D_ASSERT(atomic_read(&mdev->local_cnt));
+
+	/* I simply assume that a sector/size pair never crosses
+	 * a 16 MB extent border. (Currently this is true...) */
+	enr = BM_SECT_TO_EXT(sector);
+
+	e = lc_get(mdev->resync, enr);
+	if (e) {
+		struct bm_extent *ext = lc_entry(e, struct bm_extent, lce);
+		if (ext->lce.lc_number == enr) {
+			if (success)
+				ext->rs_left -= count;
+			else
+				ext->rs_failed += count;
+			if (ext->rs_left < ext->rs_failed) {
+				dev_err(DEV, "BAD! sector=%llus enr=%u rs_left=%d "
+				    "rs_failed=%d count=%d\n",
+				     (unsigned long long)sector,
+				     ext->lce.lc_number, ext->rs_left,
+				     ext->rs_failed, count);
+				dump_stack();
+
+				lc_put(mdev->resync, &ext->lce);
+				drbd_force_state(mdev, NS(conn, C_DISCONNECTING));
+				return;
+			}
+		} else {
+			/* Normally this element should be in the cache,
+			 * since drbd_rs_begin_io() pulled it already in.
+			 *
+			 * But maybe an application write finished, and we set
+			 * something outside the resync lru_cache in sync.
+			 */
+			int rs_left = drbd_bm_e_weight(mdev, enr);
+			if (ext->flags != 0) {
+				dev_warn(DEV, "changing resync lce: %d[%u;%02lx]"
+				     " -> %d[%u;00]\n",
+				     ext->lce.lc_number, ext->rs_left,
+				     ext->flags, enr, rs_left);
+				ext->flags = 0;
+			}
+			if (ext->rs_failed) {
+				dev_warn(DEV, "Kicking resync_lru element enr=%u "
+				     "out with rs_failed=%d\n",
+				     ext->lce.lc_number, ext->rs_failed);
+				set_bit(WRITE_BM_AFTER_RESYNC, &mdev->flags);
+			}
+			ext->rs_left = rs_left;
+			ext->rs_failed = success ? 0 : count;
+			lc_changed(mdev->resync, &ext->lce);
+		}
+		lc_put(mdev->resync, &ext->lce);
+		/* no race, we are within the al_lock! */
+
+		if (ext->rs_left == ext->rs_failed) {
+			ext->rs_failed = 0;
+
+			udw = kmalloc(sizeof(*udw), GFP_ATOMIC);
+			if (udw) {
+				udw->enr = ext->lce.lc_number;
+				udw->w.cb = w_update_odbm;
+				drbd_queue_work_front(&mdev->data.work, &udw->w);
+			} else {
+				dev_warn(DEV, "Could not kmalloc an udw\n");
+				set_bit(WRITE_BM_AFTER_RESYNC, &mdev->flags);
+			}
+		}
+	} else {
+		dev_err(DEV, "lc_get() failed! locked=%d/%d flags=%lu\n",
+		    mdev->resync_locked,
+		    mdev->resync->nr_elements,
+		    mdev->resync->flags);
+	}
+}
+
+/* clear the bit corresponding to the piece of storage in question:
+ * size byte of data starting from sector.  Only clear a bits of the affected
+ * one ore more _aligned_ BM_BLOCK_SIZE blocks.
+ *
+ * called by worker on C_SYNC_TARGET and receiver on SyncSource.
+ *
+ */
+void __drbd_set_in_sync(struct drbd_conf *mdev, sector_t sector, int size,
+		       const char *file, const unsigned int line)
+{
+	/* Is called from worker and receiver context _only_ */
+	unsigned long sbnr, ebnr, lbnr;
+	unsigned long count = 0;
+	sector_t esector, nr_sectors;
+	int wake_up = 0;
+	unsigned long flags;
+
+	if (size <= 0 || (size & 0x1ff) != 0 || size > DRBD_MAX_SEGMENT_SIZE) {
+		dev_err(DEV, "drbd_set_in_sync: sector=%llus size=%d nonsense!\n",
+				(unsigned long long)sector, size);
+		return;
+	}
+	nr_sectors = drbd_get_capacity(mdev->this_bdev);
+	esector = sector + (size >> 9) - 1;
+
+	ERR_IF(sector >= nr_sectors) return;
+	ERR_IF(esector >= nr_sectors) esector = (nr_sectors-1);
+
+	lbnr = BM_SECT_TO_BIT(nr_sectors-1);
+
+	/* we clear it (in sync).
+	 * round up start sector, round down end sector.  we make sure we only
+	 * clear full, aligned, BM_BLOCK_SIZE (4K) blocks */
+	if (unlikely(esector < BM_SECT_PER_BIT-1))
+		return;
+	if (unlikely(esector == (nr_sectors-1)))
+		ebnr = lbnr;
+	else
+		ebnr = BM_SECT_TO_BIT(esector - (BM_SECT_PER_BIT-1));
+	sbnr = BM_SECT_TO_BIT(sector + BM_SECT_PER_BIT-1);
+
+	trace_drbd_resync(mdev, TRACE_LVL_METRICS,
+			  "drbd_set_in_sync: sector=%llus size=%u sbnr=%lu ebnr=%lu\n",
+			  (unsigned long long)sector, size, sbnr, ebnr);
+
+	if (sbnr > ebnr)
+		return;
+
+	/*
+	 * ok, (capacity & 7) != 0 sometimes, but who cares...
+	 * we count rs_{total,left} in bits, not sectors.
+	 */
+	spin_lock_irqsave(&mdev->al_lock, flags);
+	count = drbd_bm_clear_bits(mdev, sbnr, ebnr);
+	if (count) {
+		/* we need the lock for drbd_try_clear_on_disk_bm */
+		if (jiffies - mdev->rs_mark_time > HZ*10) {
+			/* should be rolling marks,
+			 * but we estimate only anyways. */
+			if (mdev->rs_mark_left != drbd_bm_total_weight(mdev) &&
+			    mdev->state.conn != C_PAUSED_SYNC_T &&
+			    mdev->state.conn != C_PAUSED_SYNC_S) {
+				mdev->rs_mark_time = jiffies;
+				mdev->rs_mark_left = drbd_bm_total_weight(mdev);
+			}
+		}
+		if (get_ldev(mdev)) {
+			drbd_try_clear_on_disk_bm(mdev, sector, count, TRUE);
+			put_ldev(mdev);
+		}
+		/* just wake_up unconditional now, various lc_chaged(),
+		 * lc_put() in drbd_try_clear_on_disk_bm(). */
+		wake_up = 1;
+	}
+	spin_unlock_irqrestore(&mdev->al_lock, flags);
+	if (wake_up)
+		wake_up(&mdev->al_wait);
+}
+
+/*
+ * this is intended to set one request worth of data out of sync.
+ * affects at least 1 bit,
+ * and at most 1+DRBD_MAX_SEGMENT_SIZE/BM_BLOCK_SIZE bits.
+ *
+ * called by tl_clear and drbd_send_dblock (==drbd_make_request).
+ * so this can be _any_ process.
+ */
+void __drbd_set_out_of_sync(struct drbd_conf *mdev, sector_t sector, int size,
+			    const char *file, const unsigned int line)
+{
+	unsigned long sbnr, ebnr, lbnr, flags;
+	sector_t esector, nr_sectors;
+	unsigned int enr, count;
+	struct lc_element *e;
+
+	if (size <= 0 || (size & 0x1ff) != 0 || size > DRBD_MAX_SEGMENT_SIZE) {
+		dev_err(DEV, "sector: %llus, size: %d\n",
+			(unsigned long long)sector, size);
+		return;
+	}
+
+	if (!get_ldev(mdev))
+		return; /* no disk, no metadata, no bitmap to set bits in */
+
+	nr_sectors = drbd_get_capacity(mdev->this_bdev);
+	esector = sector + (size >> 9) - 1;
+
+	ERR_IF(sector >= nr_sectors)
+		goto out;
+	ERR_IF(esector >= nr_sectors)
+		esector = (nr_sectors-1);
+
+	lbnr = BM_SECT_TO_BIT(nr_sectors-1);
+
+	/* we set it out of sync,
+	 * we do not need to round anything here */
+	sbnr = BM_SECT_TO_BIT(sector);
+	ebnr = BM_SECT_TO_BIT(esector);
+
+	trace_drbd_resync(mdev, TRACE_LVL_METRICS,
+			  "drbd_set_out_of_sync: sector=%llus size=%u sbnr=%lu ebnr=%lu\n",
+			  (unsigned long long)sector, size, sbnr, ebnr);
+
+	/* ok, (capacity & 7) != 0 sometimes, but who cares...
+	 * we count rs_{total,left} in bits, not sectors.  */
+	spin_lock_irqsave(&mdev->al_lock, flags);
+	count = drbd_bm_set_bits(mdev, sbnr, ebnr);
+
+	enr = BM_SECT_TO_EXT(sector);
+	e = lc_find(mdev->resync, enr);
+	if (e)
+		lc_entry(e, struct bm_extent, lce)->rs_left += count;
+	spin_unlock_irqrestore(&mdev->al_lock, flags);
+
+out:
+	put_ldev(mdev);
+}
+
+static
+struct bm_extent *_bme_get(struct drbd_conf *mdev, unsigned int enr)
+{
+	struct lc_element *e;
+	struct bm_extent *bm_ext;
+	int wakeup = 0;
+	unsigned long rs_flags;
+
+	spin_lock_irq(&mdev->al_lock);
+	if (mdev->resync_locked > mdev->resync->nr_elements/2) {
+		spin_unlock_irq(&mdev->al_lock);
+		return NULL;
+	}
+	e = lc_get(mdev->resync, enr);
+	bm_ext = e ? lc_entry(e, struct bm_extent, lce) : NULL;
+	if (bm_ext) {
+		if (bm_ext->lce.lc_number != enr) {
+			bm_ext->rs_left = drbd_bm_e_weight(mdev, enr);
+			bm_ext->rs_failed = 0;
+			lc_changed(mdev->resync, &bm_ext->lce);
+			wakeup = 1;
+		}
+		if (bm_ext->lce.refcnt == 1)
+			mdev->resync_locked++;
+		set_bit(BME_NO_WRITES, &bm_ext->flags);
+	}
+	rs_flags = mdev->resync->flags;
+	spin_unlock_irq(&mdev->al_lock);
+	if (wakeup)
+		wake_up(&mdev->al_wait);
+
+	if (!bm_ext) {
+		if (rs_flags & LC_STARVING)
+			dev_warn(DEV, "Have to wait for element"
+			     " (resync LRU too small?)\n");
+		BUG_ON(rs_flags & LC_DIRTY);
+	}
+
+	return bm_ext;
+}
+
+static int _is_in_al(struct drbd_conf *mdev, unsigned int enr)
+{
+	struct lc_element *al_ext;
+	int rv = 0;
+
+	spin_lock_irq(&mdev->al_lock);
+	if (unlikely(enr == mdev->act_log->new_number))
+		rv = 1;
+	else {
+		al_ext = lc_find(mdev->act_log, enr);
+		if (al_ext) {
+			if (al_ext->refcnt)
+				rv = 1;
+		}
+	}
+	spin_unlock_irq(&mdev->al_lock);
+
+	/*
+	if (unlikely(rv)) {
+		dev_info(DEV, "Delaying sync read until app's write is done\n");
+	}
+	*/
+	return rv;
+}
+
+/**
+ * drbd_rs_begin_io() - Gets an extent in the resync LRU cache and sets it to BME_LOCKED
+ * @mdev:	DRBD device.
+ * @sector:	The sector number.
+ *
+ * This functions sleeps on al_wait. Returns 1 on success, 0 if interrupted.
+ */
+int drbd_rs_begin_io(struct drbd_conf *mdev, sector_t sector)
+{
+	unsigned int enr = BM_SECT_TO_EXT(sector);
+	struct bm_extent *bm_ext;
+	int i, sig;
+
+	trace_drbd_resync(mdev, TRACE_LVL_ALL,
+			  "drbd_rs_begin_io: sector=%llus (rs_end=%d)\n",
+			  (unsigned long long)sector, enr);
+
+	sig = wait_event_interruptible(mdev->al_wait,
+			(bm_ext = _bme_get(mdev, enr)));
+	if (sig)
+		return 0;
+
+	if (test_bit(BME_LOCKED, &bm_ext->flags))
+		return 1;
+
+	for (i = 0; i < AL_EXT_PER_BM_SECT; i++) {
+		sig = wait_event_interruptible(mdev->al_wait,
+				!_is_in_al(mdev, enr * AL_EXT_PER_BM_SECT + i));
+		if (sig) {
+			spin_lock_irq(&mdev->al_lock);
+			if (lc_put(mdev->resync, &bm_ext->lce) == 0) {
+				clear_bit(BME_NO_WRITES, &bm_ext->flags);
+				mdev->resync_locked--;
+				wake_up(&mdev->al_wait);
+			}
+			spin_unlock_irq(&mdev->al_lock);
+			return 0;
+		}
+	}
+
+	set_bit(BME_LOCKED, &bm_ext->flags);
+
+	return 1;
+}
+
+/**
+ * drbd_try_rs_begin_io() - Gets an extent in the resync LRU cache, does not sleep
+ * @mdev:	DRBD device.
+ * @sector:	The sector number.
+ *
+ * Gets an extent in the resync LRU cache, sets it to BME_NO_WRITES, then
+ * tries to set it to BME_LOCKED. Returns 0 upon success, and -EAGAIN
+ * if there is still application IO going on in this area.
+ */
+int drbd_try_rs_begin_io(struct drbd_conf *mdev, sector_t sector)
+{
+	unsigned int enr = BM_SECT_TO_EXT(sector);
+	const unsigned int al_enr = enr*AL_EXT_PER_BM_SECT;
+	struct lc_element *e;
+	struct bm_extent *bm_ext;
+	int i;
+
+	trace_drbd_resync(mdev, TRACE_LVL_ALL, "drbd_try_rs_begin_io: sector=%llus\n",
+			  (unsigned long long)sector);
+
+	spin_lock_irq(&mdev->al_lock);
+	if (mdev->resync_wenr != LC_FREE && mdev->resync_wenr != enr) {
+		/* in case you have very heavy scattered io, it may
+		 * stall the syncer undefined if we give up the ref count
+		 * when we try again and requeue.
+		 *
+		 * if we don't give up the refcount, but the next time
+		 * we are scheduled this extent has been "synced" by new
+		 * application writes, we'd miss the lc_put on the
+		 * extent we keep the refcount on.
+		 * so we remembered which extent we had to try again, and
+		 * if the next requested one is something else, we do
+		 * the lc_put here...
+		 * we also have to wake_up
+		 */
+
+		trace_drbd_resync(mdev, TRACE_LVL_ALL,
+				  "dropping %u, apparently got 'synced' by application io\n",
+				  mdev->resync_wenr);
+
+		e = lc_find(mdev->resync, mdev->resync_wenr);
+		bm_ext = e ? lc_entry(e, struct bm_extent, lce) : NULL;
+		if (bm_ext) {
+			D_ASSERT(!test_bit(BME_LOCKED, &bm_ext->flags));
+			D_ASSERT(test_bit(BME_NO_WRITES, &bm_ext->flags));
+			clear_bit(BME_NO_WRITES, &bm_ext->flags);
+			mdev->resync_wenr = LC_FREE;
+			if (lc_put(mdev->resync, &bm_ext->lce) == 0)
+				mdev->resync_locked--;
+			wake_up(&mdev->al_wait);
+		} else {
+			dev_alert(DEV, "LOGIC BUG\n");
+		}
+	}
+	/* TRY. */
+	e = lc_try_get(mdev->resync, enr);
+	bm_ext = e ? lc_entry(e, struct bm_extent, lce) : NULL;
+	if (bm_ext) {
+		if (test_bit(BME_LOCKED, &bm_ext->flags))
+			goto proceed;
+		if (!test_and_set_bit(BME_NO_WRITES, &bm_ext->flags)) {
+			mdev->resync_locked++;
+		} else {
+			/* we did set the BME_NO_WRITES,
+			 * but then could not set BME_LOCKED,
+			 * so we tried again.
+			 * drop the extra reference. */
+			trace_drbd_resync(mdev, TRACE_LVL_ALL,
+					  "dropping extra reference on %u\n", enr);
+
+			bm_ext->lce.refcnt--;
+			D_ASSERT(bm_ext->lce.refcnt > 0);
+		}
+		goto check_al;
+	} else {
+		/* do we rather want to try later? */
+		if (mdev->resync_locked > mdev->resync->nr_elements-3) {
+			trace_drbd_resync(mdev, TRACE_LVL_ALL,
+					  "resync_locked = %u!\n", mdev->resync_locked);
+
+			goto try_again;
+		}
+		/* Do or do not. There is no try. -- Yoda */
+		e = lc_get(mdev->resync, enr);
+		bm_ext = e ? lc_entry(e, struct bm_extent, lce) : NULL;
+		if (!bm_ext) {
+			const unsigned long rs_flags = mdev->resync->flags;
+			if (rs_flags & LC_STARVING)
+				dev_warn(DEV, "Have to wait for element"
+				     " (resync LRU too small?)\n");
+			BUG_ON(rs_flags & LC_DIRTY);
+			goto try_again;
+		}
+		if (bm_ext->lce.lc_number != enr) {
+			bm_ext->rs_left = drbd_bm_e_weight(mdev, enr);
+			bm_ext->rs_failed = 0;
+			lc_changed(mdev->resync, &bm_ext->lce);
+			wake_up(&mdev->al_wait);
+			D_ASSERT(test_bit(BME_LOCKED, &bm_ext->flags) == 0);
+		}
+		set_bit(BME_NO_WRITES, &bm_ext->flags);
+		D_ASSERT(bm_ext->lce.refcnt == 1);
+		mdev->resync_locked++;
+		goto check_al;
+	}
+check_al:
+	trace_drbd_resync(mdev, TRACE_LVL_ALL, "checking al for %u\n", enr);
+
+	for (i = 0; i < AL_EXT_PER_BM_SECT; i++) {
+		if (unlikely(al_enr+i == mdev->act_log->new_number))
+			goto try_again;
+		if (lc_is_used(mdev->act_log, al_enr+i))
+			goto try_again;
+	}
+	set_bit(BME_LOCKED, &bm_ext->flags);
+proceed:
+	mdev->resync_wenr = LC_FREE;
+	spin_unlock_irq(&mdev->al_lock);
+	return 0;
+
+try_again:
+	trace_drbd_resync(mdev, TRACE_LVL_ALL, "need to try again for %u\n", enr);
+	if (bm_ext)
+		mdev->resync_wenr = enr;
+	spin_unlock_irq(&mdev->al_lock);
+	return -EAGAIN;
+}
+
+void drbd_rs_complete_io(struct drbd_conf *mdev, sector_t sector)
+{
+	unsigned int enr = BM_SECT_TO_EXT(sector);
+	struct lc_element *e;
+	struct bm_extent *bm_ext;
+	unsigned long flags;
+
+	trace_drbd_resync(mdev, TRACE_LVL_ALL,
+			  "drbd_rs_complete_io: sector=%llus (rs_enr=%d)\n",
+			  (long long)sector, enr);
+
+	spin_lock_irqsave(&mdev->al_lock, flags);
+	e = lc_find(mdev->resync, enr);
+	bm_ext = e ? lc_entry(e, struct bm_extent, lce) : NULL;
+	if (!bm_ext) {
+		spin_unlock_irqrestore(&mdev->al_lock, flags);
+		if (__ratelimit(&drbd_ratelimit_state))
+			dev_err(DEV, "drbd_rs_complete_io() called, but extent not found\n");
+		return;
+	}
+
+	if (bm_ext->lce.refcnt == 0) {
+		spin_unlock_irqrestore(&mdev->al_lock, flags);
+		dev_err(DEV, "drbd_rs_complete_io(,%llu [=%u]) called, "
+		    "but refcnt is 0!?\n",
+		    (unsigned long long)sector, enr);
+		return;
+	}
+
+	if (lc_put(mdev->resync, &bm_ext->lce) == 0) {
+		clear_bit(BME_LOCKED, &bm_ext->flags);
+		clear_bit(BME_NO_WRITES, &bm_ext->flags);
+		mdev->resync_locked--;
+		wake_up(&mdev->al_wait);
+	}
+
+	spin_unlock_irqrestore(&mdev->al_lock, flags);
+}
+
+/**
+ * drbd_rs_cancel_all() - Removes all extents from the resync LRU (even BME_LOCKED)
+ * @mdev:	DRBD device.
+ */
+void drbd_rs_cancel_all(struct drbd_conf *mdev)
+{
+	trace_drbd_resync(mdev, TRACE_LVL_METRICS, "drbd_rs_cancel_all\n");
+
+	spin_lock_irq(&mdev->al_lock);
+
+	if (get_ldev_if_state(mdev, D_FAILED)) { /* Makes sure ->resync is there. */
+		lc_reset(mdev->resync);
+		put_ldev(mdev);
+	}
+	mdev->resync_locked = 0;
+	mdev->resync_wenr = LC_FREE;
+	spin_unlock_irq(&mdev->al_lock);
+	wake_up(&mdev->al_wait);
+}
+
+/**
+ * drbd_rs_del_all() - Gracefully remove all extents from the resync LRU
+ * @mdev:	DRBD device.
+ *
+ * Returns 0 upon success, -EAGAIN if at least one reference count was
+ * not zero.
+ */
+int drbd_rs_del_all(struct drbd_conf *mdev)
+{
+	struct lc_element *e;
+	struct bm_extent *bm_ext;
+	int i;
+
+	trace_drbd_resync(mdev, TRACE_LVL_METRICS, "drbd_rs_del_all\n");
+
+	spin_lock_irq(&mdev->al_lock);
+
+	if (get_ldev_if_state(mdev, D_FAILED)) {
+		/* ok, ->resync is there. */
+		for (i = 0; i < mdev->resync->nr_elements; i++) {
+			e = lc_element_by_index(mdev->resync, i);
+			bm_ext = e ? lc_entry(e, struct bm_extent, lce) : NULL;
+			if (bm_ext->lce.lc_number == LC_FREE)
+				continue;
+			if (bm_ext->lce.lc_number == mdev->resync_wenr) {
+				dev_info(DEV, "dropping %u in drbd_rs_del_all, apparently"
+				     " got 'synced' by application io\n",
+				     mdev->resync_wenr);
+				D_ASSERT(!test_bit(BME_LOCKED, &bm_ext->flags));
+				D_ASSERT(test_bit(BME_NO_WRITES, &bm_ext->flags));
+				clear_bit(BME_NO_WRITES, &bm_ext->flags);
+				mdev->resync_wenr = LC_FREE;
+				lc_put(mdev->resync, &bm_ext->lce);
+			}
+			if (bm_ext->lce.refcnt != 0) {
+				dev_info(DEV, "Retrying drbd_rs_del_all() later. "
+				     "refcnt=%d\n", bm_ext->lce.refcnt);
+				put_ldev(mdev);
+				spin_unlock_irq(&mdev->al_lock);
+				return -EAGAIN;
+			}
+			D_ASSERT(!test_bit(BME_LOCKED, &bm_ext->flags));
+			D_ASSERT(!test_bit(BME_NO_WRITES, &bm_ext->flags));
+			lc_del(mdev->resync, &bm_ext->lce);
+		}
+		D_ASSERT(mdev->resync->used == 0);
+		put_ldev(mdev);
+	}
+	spin_unlock_irq(&mdev->al_lock);
+
+	return 0;
+}
+
+/**
+ * drbd_rs_failed_io() - Record information on a failure to resync the specified blocks
+ * @mdev:	DRBD device.
+ * @sector:	The sector number.
+ * @size:	Size of failed IO operation, in byte.
+ */
+void drbd_rs_failed_io(struct drbd_conf *mdev, sector_t sector, int size)
+{
+	/* Is called from worker and receiver context _only_ */
+	unsigned long sbnr, ebnr, lbnr;
+	unsigned long count;
+	sector_t esector, nr_sectors;
+	int wake_up = 0;
+
+	trace_drbd_resync(mdev, TRACE_LVL_SUMMARY,
+			  "drbd_rs_failed_io: sector=%llus, size=%u\n",
+			  (unsigned long long)sector, size);
+
+	if (size <= 0 || (size & 0x1ff) != 0 || size > DRBD_MAX_SEGMENT_SIZE) {
+		dev_err(DEV, "drbd_rs_failed_io: sector=%llus size=%d nonsense!\n",
+				(unsigned long long)sector, size);
+		return;
+	}
+	nr_sectors = drbd_get_capacity(mdev->this_bdev);
+	esector = sector + (size >> 9) - 1;
+
+	ERR_IF(sector >= nr_sectors) return;
+	ERR_IF(esector >= nr_sectors) esector = (nr_sectors-1);
+
+	lbnr = BM_SECT_TO_BIT(nr_sectors-1);
+
+	/*
+	 * round up start sector, round down end sector.  we make sure we only
+	 * handle full, aligned, BM_BLOCK_SIZE (4K) blocks */
+	if (unlikely(esector < BM_SECT_PER_BIT-1))
+		return;
+	if (unlikely(esector == (nr_sectors-1)))
+		ebnr = lbnr;
+	else
+		ebnr = BM_SECT_TO_BIT(esector - (BM_SECT_PER_BIT-1));
+	sbnr = BM_SECT_TO_BIT(sector + BM_SECT_PER_BIT-1);
+
+	if (sbnr > ebnr)
+		return;
+
+	/*
+	 * ok, (capacity & 7) != 0 sometimes, but who cares...
+	 * we count rs_{total,left} in bits, not sectors.
+	 */
+	spin_lock_irq(&mdev->al_lock);
+	count = drbd_bm_count_bits(mdev, sbnr, ebnr);
+	if (count) {
+		mdev->rs_failed += count;
+
+		if (get_ldev(mdev)) {
+			drbd_try_clear_on_disk_bm(mdev, sector, count, FALSE);
+			put_ldev(mdev);
+		}
+
+		/* just wake_up unconditional now, various lc_chaged(),
+		 * lc_put() in drbd_try_clear_on_disk_bm(). */
+		wake_up = 1;
+	}
+	spin_unlock_irq(&mdev->al_lock);
+	if (wake_up)
+		wake_up(&mdev->al_wait);
+}
diff --git a/drivers/block/drbd/drbd_bitmap.c b/drivers/block/drbd/drbd_bitmap.c
new file mode 100644
index 00000000000..b61057e7788
--- /dev/null
+++ b/drivers/block/drbd/drbd_bitmap.c
@@ -0,0 +1,1327 @@
+/*
+   drbd_bitmap.c
+
+   This file is part of DRBD by Philipp Reisner and Lars Ellenberg.
+
+   Copyright (C) 2004-2008, LINBIT Information Technologies GmbH.
+   Copyright (C) 2004-2008, Philipp Reisner <philipp.reisner@linbit.com>.
+   Copyright (C) 2004-2008, Lars Ellenberg <lars.ellenberg@linbit.com>.
+
+   drbd is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 2, or (at your option)
+   any later version.
+
+   drbd is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with drbd; see the file COPYING.  If not, write to
+   the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#include <linux/bitops.h>
+#include <linux/vmalloc.h>
+#include <linux/string.h>
+#include <linux/drbd.h>
+#include <asm/kmap_types.h>
+#include "drbd_int.h"
+
+/* OPAQUE outside this file!
+ * interface defined in drbd_int.h
+
+ * convention:
+ * function name drbd_bm_... => used elsewhere, "public".
+ * function name      bm_... => internal to implementation, "private".
+
+ * Note that since find_first_bit returns int, at the current granularity of
+ * the bitmap (4KB per byte), this implementation "only" supports up to
+ * 1<<(32+12) == 16 TB...
+ */
+
+/*
+ * NOTE
+ *  Access to the *bm_pages is protected by bm_lock.
+ *  It is safe to read the other members within the lock.
+ *
+ *  drbd_bm_set_bits is called from bio_endio callbacks,
+ *  We may be called with irq already disabled,
+ *  so we need spin_lock_irqsave().
+ *  And we need the kmap_atomic.
+ */
+struct drbd_bitmap {
+	struct page **bm_pages;
+	spinlock_t bm_lock;
+	/* WARNING unsigned long bm_*:
+	 * 32bit number of bit offset is just enough for 512 MB bitmap.
+	 * it will blow up if we make the bitmap bigger...
+	 * not that it makes much sense to have a bitmap that large,
+	 * rather change the granularity to 16k or 64k or something.
+	 * (that implies other problems, however...)
+	 */
+	unsigned long bm_set;       /* nr of set bits; THINK maybe atomic_t? */
+	unsigned long bm_bits;
+	size_t   bm_words;
+	size_t   bm_number_of_pages;
+	sector_t bm_dev_capacity;
+	struct semaphore bm_change; /* serializes resize operations */
+
+	atomic_t bm_async_io;
+	wait_queue_head_t bm_io_wait;
+
+	unsigned long  bm_flags;
+
+	/* debugging aid, in case we are still racy somewhere */
+	char          *bm_why;
+	struct task_struct *bm_task;
+};
+
+/* definition of bits in bm_flags */
+#define BM_LOCKED       0
+#define BM_MD_IO_ERROR  1
+#define BM_P_VMALLOCED  2
+
+static int bm_is_locked(struct drbd_bitmap *b)
+{
+	return test_bit(BM_LOCKED, &b->bm_flags);
+}
+
+#define bm_print_lock_info(m) __bm_print_lock_info(m, __func__)
+static void __bm_print_lock_info(struct drbd_conf *mdev, const char *func)
+{
+	struct drbd_bitmap *b = mdev->bitmap;
+	if (!__ratelimit(&drbd_ratelimit_state))
+		return;
+	dev_err(DEV, "FIXME %s in %s, bitmap locked for '%s' by %s\n",
+	    current == mdev->receiver.task ? "receiver" :
+	    current == mdev->asender.task  ? "asender"  :
+	    current == mdev->worker.task   ? "worker"   : current->comm,
+	    func, b->bm_why ?: "?",
+	    b->bm_task == mdev->receiver.task ? "receiver" :
+	    b->bm_task == mdev->asender.task  ? "asender"  :
+	    b->bm_task == mdev->worker.task   ? "worker"   : "?");
+}
+
+void drbd_bm_lock(struct drbd_conf *mdev, char *why)
+{
+	struct drbd_bitmap *b = mdev->bitmap;
+	int trylock_failed;
+
+	if (!b) {
+		dev_err(DEV, "FIXME no bitmap in drbd_bm_lock!?\n");
+		return;
+	}
+
+	trylock_failed = down_trylock(&b->bm_change);
+
+	if (trylock_failed) {
+		dev_warn(DEV, "%s going to '%s' but bitmap already locked for '%s' by %s\n",
+		    current == mdev->receiver.task ? "receiver" :
+		    current == mdev->asender.task  ? "asender"  :
+		    current == mdev->worker.task   ? "worker"   : current->comm,
+		    why, b->bm_why ?: "?",
+		    b->bm_task == mdev->receiver.task ? "receiver" :
+		    b->bm_task == mdev->asender.task  ? "asender"  :
+		    b->bm_task == mdev->worker.task   ? "worker"   : "?");
+		down(&b->bm_change);
+	}
+	if (__test_and_set_bit(BM_LOCKED, &b->bm_flags))
+		dev_err(DEV, "FIXME bitmap already locked in bm_lock\n");
+
+	b->bm_why  = why;
+	b->bm_task = current;
+}
+
+void drbd_bm_unlock(struct drbd_conf *mdev)
+{
+	struct drbd_bitmap *b = mdev->bitmap;
+	if (!b) {
+		dev_err(DEV, "FIXME no bitmap in drbd_bm_unlock!?\n");
+		return;
+	}
+
+	if (!__test_and_clear_bit(BM_LOCKED, &mdev->bitmap->bm_flags))
+		dev_err(DEV, "FIXME bitmap not locked in bm_unlock\n");
+
+	b->bm_why  = NULL;
+	b->bm_task = NULL;
+	up(&b->bm_change);
+}
+
+/* word offset to long pointer */
+static unsigned long *__bm_map_paddr(struct drbd_bitmap *b, unsigned long offset, const enum km_type km)
+{
+	struct page *page;
+	unsigned long page_nr;
+
+	/* page_nr = (word*sizeof(long)) >> PAGE_SHIFT; */
+	page_nr = offset >> (PAGE_SHIFT - LN2_BPL + 3);
+	BUG_ON(page_nr >= b->bm_number_of_pages);
+	page = b->bm_pages[page_nr];
+
+	return (unsigned long *) kmap_atomic(page, km);
+}
+
+static unsigned long * bm_map_paddr(struct drbd_bitmap *b, unsigned long offset)
+{
+	return __bm_map_paddr(b, offset, KM_IRQ1);
+}
+
+static void __bm_unmap(unsigned long *p_addr, const enum km_type km)
+{
+	kunmap_atomic(p_addr, km);
+};
+
+static void bm_unmap(unsigned long *p_addr)
+{
+	return __bm_unmap(p_addr, KM_IRQ1);
+}
+
+/* long word offset of _bitmap_ sector */
+#define S2W(s)	((s)<<(BM_EXT_SHIFT-BM_BLOCK_SHIFT-LN2_BPL))
+/* word offset from start of bitmap to word number _in_page_
+ * modulo longs per page
+#define MLPP(X) ((X) % (PAGE_SIZE/sizeof(long))
+ hm, well, Philipp thinks gcc might not optimze the % into & (... - 1)
+ so do it explicitly:
+ */
+#define MLPP(X) ((X) & ((PAGE_SIZE/sizeof(long))-1))
+
+/* Long words per page */
+#define LWPP (PAGE_SIZE/sizeof(long))
+
+/*
+ * actually most functions herein should take a struct drbd_bitmap*, not a
+ * struct drbd_conf*, but for the debug macros I like to have the mdev around
+ * to be able to report device specific.
+ */
+
+static void bm_free_pages(struct page **pages, unsigned long number)
+{
+	unsigned long i;
+	if (!pages)
+		return;
+
+	for (i = 0; i < number; i++) {
+		if (!pages[i]) {
+			printk(KERN_ALERT "drbd: bm_free_pages tried to free "
+					  "a NULL pointer; i=%lu n=%lu\n",
+					  i, number);
+			continue;
+		}
+		__free_page(pages[i]);
+		pages[i] = NULL;
+	}
+}
+
+static void bm_vk_free(void *ptr, int v)
+{
+	if (v)
+		vfree(ptr);
+	else
+		kfree(ptr);
+}
+
+/*
+ * "have" and "want" are NUMBER OF PAGES.
+ */
+static struct page **bm_realloc_pages(struct drbd_bitmap *b, unsigned long want)
+{
+	struct page **old_pages = b->bm_pages;
+	struct page **new_pages, *page;
+	unsigned int i, bytes, vmalloced = 0;
+	unsigned long have = b->bm_number_of_pages;
+
+	BUG_ON(have == 0 && old_pages != NULL);
+	BUG_ON(have != 0 && old_pages == NULL);
+
+	if (have == want)
+		return old_pages;
+
+	/* Trying kmalloc first, falling back to vmalloc.
+	 * GFP_KERNEL is ok, as this is done when a lower level disk is
+	 * "attached" to the drbd.  Context is receiver thread or cqueue
+	 * thread.  As we have no disk yet, we are not in the IO path,
+	 * not even the IO path of the peer. */
+	bytes = sizeof(struct page *)*want;
+	new_pages = kmalloc(bytes, GFP_KERNEL);
+	if (!new_pages) {
+		new_pages = vmalloc(bytes);
+		if (!new_pages)
+			return NULL;
+		vmalloced = 1;
+	}
+
+	memset(new_pages, 0, bytes);
+	if (want >= have) {
+		for (i = 0; i < have; i++)
+			new_pages[i] = old_pages[i];
+		for (; i < want; i++) {
+			page = alloc_page(GFP_HIGHUSER);
+			if (!page) {
+				bm_free_pages(new_pages + have, i - have);
+				bm_vk_free(new_pages, vmalloced);
+				return NULL;
+			}
+			new_pages[i] = page;
+		}
+	} else {
+		for (i = 0; i < want; i++)
+			new_pages[i] = old_pages[i];
+		/* NOT HERE, we are outside the spinlock!
+		bm_free_pages(old_pages + want, have - want);
+		*/
+	}
+
+	if (vmalloced)
+		set_bit(BM_P_VMALLOCED, &b->bm_flags);
+	else
+		clear_bit(BM_P_VMALLOCED, &b->bm_flags);
+
+	return new_pages;
+}
+
+/*
+ * called on driver init only. TODO call when a device is created.
+ * allocates the drbd_bitmap, and stores it in mdev->bitmap.
+ */
+int drbd_bm_init(struct drbd_conf *mdev)
+{
+	struct drbd_bitmap *b = mdev->bitmap;
+	WARN_ON(b != NULL);
+	b = kzalloc(sizeof(struct drbd_bitmap), GFP_KERNEL);
+	if (!b)
+		return -ENOMEM;
+	spin_lock_init(&b->bm_lock);
+	init_MUTEX(&b->bm_change);
+	init_waitqueue_head(&b->bm_io_wait);
+
+	mdev->bitmap = b;
+
+	return 0;
+}
+
+sector_t drbd_bm_capacity(struct drbd_conf *mdev)
+{
+	ERR_IF(!mdev->bitmap) return 0;
+	return mdev->bitmap->bm_dev_capacity;
+}
+
+/* called on driver unload. TODO: call when a device is destroyed.
+ */
+void drbd_bm_cleanup(struct drbd_conf *mdev)
+{
+	ERR_IF (!mdev->bitmap) return;
+	bm_free_pages(mdev->bitmap->bm_pages, mdev->bitmap->bm_number_of_pages);
+	bm_vk_free(mdev->bitmap->bm_pages, test_bit(BM_P_VMALLOCED, &mdev->bitmap->bm_flags));
+	kfree(mdev->bitmap);
+	mdev->bitmap = NULL;
+}
+
+/*
+ * since (b->bm_bits % BITS_PER_LONG) != 0,
+ * this masks out the remaining bits.
+ * Returns the number of bits cleared.
+ */
+static int bm_clear_surplus(struct drbd_bitmap *b)
+{
+	const unsigned long mask = (1UL << (b->bm_bits & (BITS_PER_LONG-1))) - 1;
+	size_t w = b->bm_bits >> LN2_BPL;
+	int cleared = 0;
+	unsigned long *p_addr, *bm;
+
+	p_addr = bm_map_paddr(b, w);
+	bm = p_addr + MLPP(w);
+	if (w < b->bm_words) {
+		cleared = hweight_long(*bm & ~mask);
+		*bm &= mask;
+		w++; bm++;
+	}
+
+	if (w < b->bm_words) {
+		cleared += hweight_long(*bm);
+		*bm = 0;
+	}
+	bm_unmap(p_addr);
+	return cleared;
+}
+
+static void bm_set_surplus(struct drbd_bitmap *b)
+{
+	const unsigned long mask = (1UL << (b->bm_bits & (BITS_PER_LONG-1))) - 1;
+	size_t w = b->bm_bits >> LN2_BPL;
+	unsigned long *p_addr, *bm;
+
+	p_addr = bm_map_paddr(b, w);
+	bm = p_addr + MLPP(w);
+	if (w < b->bm_words) {
+		*bm |= ~mask;
+		bm++; w++;
+	}
+
+	if (w < b->bm_words) {
+		*bm = ~(0UL);
+	}
+	bm_unmap(p_addr);
+}
+
+static unsigned long __bm_count_bits(struct drbd_bitmap *b, const int swap_endian)
+{
+	unsigned long *p_addr, *bm, offset = 0;
+	unsigned long bits = 0;
+	unsigned long i, do_now;
+
+	while (offset < b->bm_words) {
+		i = do_now = min_t(size_t, b->bm_words-offset, LWPP);
+		p_addr = __bm_map_paddr(b, offset, KM_USER0);
+		bm = p_addr + MLPP(offset);
+		while (i--) {
+#ifndef __LITTLE_ENDIAN
+			if (swap_endian)
+				*bm = lel_to_cpu(*bm);
+#endif
+			bits += hweight_long(*bm++);
+		}
+		__bm_unmap(p_addr, KM_USER0);
+		offset += do_now;
+		cond_resched();
+	}
+
+	return bits;
+}
+
+static unsigned long bm_count_bits(struct drbd_bitmap *b)
+{
+	return __bm_count_bits(b, 0);
+}
+
+static unsigned long bm_count_bits_swap_endian(struct drbd_bitmap *b)
+{
+	return __bm_count_bits(b, 1);
+}
+
+/* offset and len in long words.*/
+static void bm_memset(struct drbd_bitmap *b, size_t offset, int c, size_t len)
+{
+	unsigned long *p_addr, *bm;
+	size_t do_now, end;
+
+#define BM_SECTORS_PER_BIT (BM_BLOCK_SIZE/512)
+
+	end = offset + len;
+
+	if (end > b->bm_words) {
+		printk(KERN_ALERT "drbd: bm_memset end > bm_words\n");
+		return;
+	}
+
+	while (offset < end) {
+		do_now = min_t(size_t, ALIGN(offset + 1, LWPP), end) - offset;
+		p_addr = bm_map_paddr(b, offset);
+		bm = p_addr + MLPP(offset);
+		if (bm+do_now > p_addr + LWPP) {
+			printk(KERN_ALERT "drbd: BUG BUG BUG! p_addr:%p bm:%p do_now:%d\n",
+			       p_addr, bm, (int)do_now);
+			break; /* breaks to after catch_oob_access_end() only! */
+		}
+		memset(bm, c, do_now * sizeof(long));
+		bm_unmap(p_addr);
+		offset += do_now;
+	}
+}
+
+/*
+ * make sure the bitmap has enough room for the attached storage,
+ * if necessary, resize.
+ * called whenever we may have changed the device size.
+ * returns -ENOMEM if we could not allocate enough memory, 0 on success.
+ * In case this is actually a resize, we copy the old bitmap into the new one.
+ * Otherwise, the bitmap is initialized to all bits set.
+ */
+int drbd_bm_resize(struct drbd_conf *mdev, sector_t capacity)
+{
+	struct drbd_bitmap *b = mdev->bitmap;
+	unsigned long bits, words, owords, obits, *p_addr, *bm;
+	unsigned long want, have, onpages; /* number of pages */
+	struct page **npages, **opages = NULL;
+	int err = 0, growing;
+	int opages_vmalloced;
+
+	ERR_IF(!b) return -ENOMEM;
+
+	drbd_bm_lock(mdev, "resize");
+
+	dev_info(DEV, "drbd_bm_resize called with capacity == %llu\n",
+			(unsigned long long)capacity);
+
+	if (capacity == b->bm_dev_capacity)
+		goto out;
+
+	opages_vmalloced = test_bit(BM_P_VMALLOCED, &b->bm_flags);
+
+	if (capacity == 0) {
+		spin_lock_irq(&b->bm_lock);
+		opages = b->bm_pages;
+		onpages = b->bm_number_of_pages;
+		owords = b->bm_words;
+		b->bm_pages = NULL;
+		b->bm_number_of_pages =
+		b->bm_set   =
+		b->bm_bits  =
+		b->bm_words =
+		b->bm_dev_capacity = 0;
+		spin_unlock_irq(&b->bm_lock);
+		bm_free_pages(opages, onpages);
+		bm_vk_free(opages, opages_vmalloced);
+		goto out;
+	}
+	bits  = BM_SECT_TO_BIT(ALIGN(capacity, BM_SECT_PER_BIT));
+
+	/* if we would use
+	   words = ALIGN(bits,BITS_PER_LONG) >> LN2_BPL;
+	   a 32bit host could present the wrong number of words
+	   to a 64bit host.
+	*/
+	words = ALIGN(bits, 64) >> LN2_BPL;
+
+	if (get_ldev(mdev)) {
+		D_ASSERT((u64)bits <= (((u64)mdev->ldev->md.md_size_sect-MD_BM_OFFSET) << 12));
+		put_ldev(mdev);
+	}
+
+	/* one extra long to catch off by one errors */
+	want = ALIGN((words+1)*sizeof(long), PAGE_SIZE) >> PAGE_SHIFT;
+	have = b->bm_number_of_pages;
+	if (want == have) {
+		D_ASSERT(b->bm_pages != NULL);
+		npages = b->bm_pages;
+	} else {
+		if (FAULT_ACTIVE(mdev, DRBD_FAULT_BM_ALLOC))
+			npages = NULL;
+		else
+			npages = bm_realloc_pages(b, want);
+	}
+
+	if (!npages) {
+		err = -ENOMEM;
+		goto out;
+	}
+
+	spin_lock_irq(&b->bm_lock);
+	opages = b->bm_pages;
+	owords = b->bm_words;
+	obits  = b->bm_bits;
+
+	growing = bits > obits;
+	if (opages)
+		bm_set_surplus(b);
+
+	b->bm_pages = npages;
+	b->bm_number_of_pages = want;
+	b->bm_bits  = bits;
+	b->bm_words = words;
+	b->bm_dev_capacity = capacity;
+
+	if (growing) {
+		bm_memset(b, owords, 0xff, words-owords);
+		b->bm_set += bits - obits;
+	}
+
+	if (want < have) {
+		/* implicit: (opages != NULL) && (opages != npages) */
+		bm_free_pages(opages + want, have - want);
+	}
+
+	p_addr = bm_map_paddr(b, words);
+	bm = p_addr + MLPP(words);
+	*bm = DRBD_MAGIC;
+	bm_unmap(p_addr);
+
+	(void)bm_clear_surplus(b);
+
+	spin_unlock_irq(&b->bm_lock);
+	if (opages != npages)
+		bm_vk_free(opages, opages_vmalloced);
+	if (!growing)
+		b->bm_set = bm_count_bits(b);
+	dev_info(DEV, "resync bitmap: bits=%lu words=%lu\n", bits, words);
+
+ out:
+	drbd_bm_unlock(mdev);
+	return err;
+}
+
+/* inherently racy:
+ * if not protected by other means, return value may be out of date when
+ * leaving this function...
+ * we still need to lock it, since it is important that this returns
+ * bm_set == 0 precisely.
+ *
+ * maybe bm_set should be atomic_t ?
+ */
+static unsigned long _drbd_bm_total_weight(struct drbd_conf *mdev)
+{
+	struct drbd_bitmap *b = mdev->bitmap;
+	unsigned long s;
+	unsigned long flags;
+
+	ERR_IF(!b) return 0;
+	ERR_IF(!b->bm_pages) return 0;
+
+	spin_lock_irqsave(&b->bm_lock, flags);
+	s = b->bm_set;
+	spin_unlock_irqrestore(&b->bm_lock, flags);
+
+	return s;
+}
+
+unsigned long drbd_bm_total_weight(struct drbd_conf *mdev)
+{
+	unsigned long s;
+	/* if I don't have a disk, I don't know about out-of-sync status */
+	if (!get_ldev_if_state(mdev, D_NEGOTIATING))
+		return 0;
+	s = _drbd_bm_total_weight(mdev);
+	put_ldev(mdev);
+	return s;
+}
+
+size_t drbd_bm_words(struct drbd_conf *mdev)
+{
+	struct drbd_bitmap *b = mdev->bitmap;
+	ERR_IF(!b) return 0;
+	ERR_IF(!b->bm_pages) return 0;
+
+	return b->bm_words;
+}
+
+unsigned long drbd_bm_bits(struct drbd_conf *mdev)
+{
+	struct drbd_bitmap *b = mdev->bitmap;
+	ERR_IF(!b) return 0;
+
+	return b->bm_bits;
+}
+
+/* merge number words from buffer into the bitmap starting at offset.
+ * buffer[i] is expected to be little endian unsigned long.
+ * bitmap must be locked by drbd_bm_lock.
+ * currently only used from receive_bitmap.
+ */
+void drbd_bm_merge_lel(struct drbd_conf *mdev, size_t offset, size_t number,
+			unsigned long *buffer)
+{
+	struct drbd_bitmap *b = mdev->bitmap;
+	unsigned long *p_addr, *bm;
+	unsigned long word, bits;
+	size_t end, do_now;
+
+	end = offset + number;
+
+	ERR_IF(!b) return;
+	ERR_IF(!b->bm_pages) return;
+	if (number == 0)
+		return;
+	WARN_ON(offset >= b->bm_words);
+	WARN_ON(end    >  b->bm_words);
+
+	spin_lock_irq(&b->bm_lock);
+	while (offset < end) {
+		do_now = min_t(size_t, ALIGN(offset+1, LWPP), end) - offset;
+		p_addr = bm_map_paddr(b, offset);
+		bm = p_addr + MLPP(offset);
+		offset += do_now;
+		while (do_now--) {
+			bits = hweight_long(*bm);
+			word = *bm | lel_to_cpu(*buffer++);
+			*bm++ = word;
+			b->bm_set += hweight_long(word) - bits;
+		}
+		bm_unmap(p_addr);
+	}
+	/* with 32bit <-> 64bit cross-platform connect
+	 * this is only correct for current usage,
+	 * where we _know_ that we are 64 bit aligned,
+	 * and know that this function is used in this way, too...
+	 */
+	if (end == b->bm_words)
+		b->bm_set -= bm_clear_surplus(b);
+
+	spin_unlock_irq(&b->bm_lock);
+}
+
+/* copy number words from the bitmap starting at offset into the buffer.
+ * buffer[i] will be little endian unsigned long.
+ */
+void drbd_bm_get_lel(struct drbd_conf *mdev, size_t offset, size_t number,
+		     unsigned long *buffer)
+{
+	struct drbd_bitmap *b = mdev->bitmap;
+	unsigned long *p_addr, *bm;
+	size_t end, do_now;
+
+	end = offset + number;
+
+	ERR_IF(!b) return;
+	ERR_IF(!b->bm_pages) return;
+
+	spin_lock_irq(&b->bm_lock);
+	if ((offset >= b->bm_words) ||
+	    (end    >  b->bm_words) ||
+	    (number <= 0))
+		dev_err(DEV, "offset=%lu number=%lu bm_words=%lu\n",
+			(unsigned long)	offset,
+			(unsigned long)	number,
+			(unsigned long) b->bm_words);
+	else {
+		while (offset < end) {
+			do_now = min_t(size_t, ALIGN(offset+1, LWPP), end) - offset;
+			p_addr = bm_map_paddr(b, offset);
+			bm = p_addr + MLPP(offset);
+			offset += do_now;
+			while (do_now--)
+				*buffer++ = cpu_to_lel(*bm++);
+			bm_unmap(p_addr);
+		}
+	}
+	spin_unlock_irq(&b->bm_lock);
+}
+
+/* set all bits in the bitmap */
+void drbd_bm_set_all(struct drbd_conf *mdev)
+{
+	struct drbd_bitmap *b = mdev->bitmap;
+	ERR_IF(!b) return;
+	ERR_IF(!b->bm_pages) return;
+
+	spin_lock_irq(&b->bm_lock);
+	bm_memset(b, 0, 0xff, b->bm_words);
+	(void)bm_clear_surplus(b);
+	b->bm_set = b->bm_bits;
+	spin_unlock_irq(&b->bm_lock);
+}
+
+/* clear all bits in the bitmap */
+void drbd_bm_clear_all(struct drbd_conf *mdev)
+{
+	struct drbd_bitmap *b = mdev->bitmap;
+	ERR_IF(!b) return;
+	ERR_IF(!b->bm_pages) return;
+
+	spin_lock_irq(&b->bm_lock);
+	bm_memset(b, 0, 0, b->bm_words);
+	b->bm_set = 0;
+	spin_unlock_irq(&b->bm_lock);
+}
+
+static void bm_async_io_complete(struct bio *bio, int error)
+{
+	struct drbd_bitmap *b = bio->bi_private;
+	int uptodate = bio_flagged(bio, BIO_UPTODATE);
+
+
+	/* strange behavior of some lower level drivers...
+	 * fail the request by clearing the uptodate flag,
+	 * but do not return any error?!
+	 * do we want to WARN() on this? */
+	if (!error && !uptodate)
+		error = -EIO;
+
+	if (error) {
+		/* doh. what now?
+		 * for now, set all bits, and flag MD_IO_ERROR */
+		__set_bit(BM_MD_IO_ERROR, &b->bm_flags);
+	}
+	if (atomic_dec_and_test(&b->bm_async_io))
+		wake_up(&b->bm_io_wait);
+
+	bio_put(bio);
+}
+
+static void bm_page_io_async(struct drbd_conf *mdev, struct drbd_bitmap *b, int page_nr, int rw) __must_hold(local)
+{
+	/* we are process context. we always get a bio */
+	struct bio *bio = bio_alloc(GFP_KERNEL, 1);
+	unsigned int len;
+	sector_t on_disk_sector =
+		mdev->ldev->md.md_offset + mdev->ldev->md.bm_offset;
+	on_disk_sector += ((sector_t)page_nr) << (PAGE_SHIFT-9);
+
+	/* this might happen with very small
+	 * flexible external meta data device */
+	len = min_t(unsigned int, PAGE_SIZE,
+		(drbd_md_last_sector(mdev->ldev) - on_disk_sector + 1)<<9);
+
+	bio->bi_bdev = mdev->ldev->md_bdev;
+	bio->bi_sector = on_disk_sector;
+	bio_add_page(bio, b->bm_pages[page_nr], len, 0);
+	bio->bi_private = b;
+	bio->bi_end_io = bm_async_io_complete;
+
+	if (FAULT_ACTIVE(mdev, (rw & WRITE) ? DRBD_FAULT_MD_WR : DRBD_FAULT_MD_RD)) {
+		bio->bi_rw |= rw;
+		bio_endio(bio, -EIO);
+	} else {
+		submit_bio(rw, bio);
+	}
+}
+
+# if defined(__LITTLE_ENDIAN)
+	/* nothing to do, on disk == in memory */
+# define bm_cpu_to_lel(x) ((void)0)
+# else
+void bm_cpu_to_lel(struct drbd_bitmap *b)
+{
+	/* need to cpu_to_lel all the pages ...
+	 * this may be optimized by using
+	 * cpu_to_lel(-1) == -1 and cpu_to_lel(0) == 0;
+	 * the following is still not optimal, but better than nothing */
+	unsigned int i;
+	unsigned long *p_addr, *bm;
+	if (b->bm_set == 0) {
+		/* no page at all; avoid swap if all is 0 */
+		i = b->bm_number_of_pages;
+	} else if (b->bm_set == b->bm_bits) {
+		/* only the last page */
+		i = b->bm_number_of_pages - 1;
+	} else {
+		/* all pages */
+		i = 0;
+	}
+	for (; i < b->bm_number_of_pages; i++) {
+		p_addr = kmap_atomic(b->bm_pages[i], KM_USER0);
+		for (bm = p_addr; bm < p_addr + PAGE_SIZE/sizeof(long); bm++)
+			*bm = cpu_to_lel(*bm);
+		kunmap_atomic(p_addr, KM_USER0);
+	}
+}
+# endif
+/* lel_to_cpu == cpu_to_lel */
+# define bm_lel_to_cpu(x) bm_cpu_to_lel(x)
+
+/*
+ * bm_rw: read/write the whole bitmap from/to its on disk location.
+ */
+static int bm_rw(struct drbd_conf *mdev, int rw) __must_hold(local)
+{
+	struct drbd_bitmap *b = mdev->bitmap;
+	/* sector_t sector; */
+	int bm_words, num_pages, i;
+	unsigned long now;
+	char ppb[10];
+	int err = 0;
+
+	WARN_ON(!bm_is_locked(b));
+
+	/* no spinlock here, the drbd_bm_lock should be enough! */
+
+	bm_words  = drbd_bm_words(mdev);
+	num_pages = (bm_words*sizeof(long) + PAGE_SIZE-1) >> PAGE_SHIFT;
+
+	/* on disk bitmap is little endian */
+	if (rw == WRITE)
+		bm_cpu_to_lel(b);
+
+	now = jiffies;
+	atomic_set(&b->bm_async_io, num_pages);
+	__clear_bit(BM_MD_IO_ERROR, &b->bm_flags);
+
+	/* let the layers below us try to merge these bios... */
+	for (i = 0; i < num_pages; i++)
+		bm_page_io_async(mdev, b, i, rw);
+
+	drbd_blk_run_queue(bdev_get_queue(mdev->ldev->md_bdev));
+	wait_event(b->bm_io_wait, atomic_read(&b->bm_async_io) == 0);
+
+	if (test_bit(BM_MD_IO_ERROR, &b->bm_flags)) {
+		dev_alert(DEV, "we had at least one MD IO ERROR during bitmap IO\n");
+		drbd_chk_io_error(mdev, 1, TRUE);
+		err = -EIO;
+	}
+
+	now = jiffies;
+	if (rw == WRITE) {
+		/* swap back endianness */
+		bm_lel_to_cpu(b);
+		/* flush bitmap to stable storage */
+		drbd_md_flush(mdev);
+	} else /* rw == READ */ {
+		/* just read, if necessary adjust endianness */
+		b->bm_set = bm_count_bits_swap_endian(b);
+		dev_info(DEV, "recounting of set bits took additional %lu jiffies\n",
+		     jiffies - now);
+	}
+	now = b->bm_set;
+
+	dev_info(DEV, "%s (%lu bits) marked out-of-sync by on disk bit-map.\n",
+	     ppsize(ppb, now << (BM_BLOCK_SHIFT-10)), now);
+
+	return err;
+}
+
+/**
+ * drbd_bm_read() - Read the whole bitmap from its on disk location.
+ * @mdev:	DRBD device.
+ */
+int drbd_bm_read(struct drbd_conf *mdev) __must_hold(local)
+{
+	return bm_rw(mdev, READ);
+}
+
+/**
+ * drbd_bm_write() - Write the whole bitmap to its on disk location.
+ * @mdev:	DRBD device.
+ */
+int drbd_bm_write(struct drbd_conf *mdev) __must_hold(local)
+{
+	return bm_rw(mdev, WRITE);
+}
+
+/**
+ * drbd_bm_write_sect: Writes a 512 (MD_SECTOR_SIZE) byte piece of the bitmap
+ * @mdev:	DRBD device.
+ * @enr:	Extent number in the resync lru (happens to be sector offset)
+ *
+ * The BM_EXT_SIZE is on purpose exactly the amount of the bitmap covered
+ * by a single sector write. Therefore enr == sector offset from the
+ * start of the bitmap.
+ */
+int drbd_bm_write_sect(struct drbd_conf *mdev, unsigned long enr) __must_hold(local)
+{
+	sector_t on_disk_sector = enr + mdev->ldev->md.md_offset
+				      + mdev->ldev->md.bm_offset;
+	int bm_words, num_words, offset;
+	int err = 0;
+
+	mutex_lock(&mdev->md_io_mutex);
+	bm_words  = drbd_bm_words(mdev);
+	offset    = S2W(enr);	/* word offset into bitmap */
+	num_words = min(S2W(1), bm_words - offset);
+	if (num_words < S2W(1))
+		memset(page_address(mdev->md_io_page), 0, MD_SECTOR_SIZE);
+	drbd_bm_get_lel(mdev, offset, num_words,
+			page_address(mdev->md_io_page));
+	if (!drbd_md_sync_page_io(mdev, mdev->ldev, on_disk_sector, WRITE)) {
+		int i;
+		err = -EIO;
+		dev_err(DEV, "IO ERROR writing bitmap sector %lu "
+		    "(meta-disk sector %llus)\n",
+		    enr, (unsigned long long)on_disk_sector);
+		drbd_chk_io_error(mdev, 1, TRUE);
+		for (i = 0; i < AL_EXT_PER_BM_SECT; i++)
+			drbd_bm_ALe_set_all(mdev, enr*AL_EXT_PER_BM_SECT+i);
+	}
+	mdev->bm_writ_cnt++;
+	mutex_unlock(&mdev->md_io_mutex);
+	return err;
+}
+
+/* NOTE
+ * find_first_bit returns int, we return unsigned long.
+ * should not make much difference anyways, but ...
+ *
+ * this returns a bit number, NOT a sector!
+ */
+#define BPP_MASK ((1UL << (PAGE_SHIFT+3)) - 1)
+static unsigned long __bm_find_next(struct drbd_conf *mdev, unsigned long bm_fo,
+	const int find_zero_bit, const enum km_type km)
+{
+	struct drbd_bitmap *b = mdev->bitmap;
+	unsigned long i = -1UL;
+	unsigned long *p_addr;
+	unsigned long bit_offset; /* bit offset of the mapped page. */
+
+	if (bm_fo > b->bm_bits) {
+		dev_err(DEV, "bm_fo=%lu bm_bits=%lu\n", bm_fo, b->bm_bits);
+	} else {
+		while (bm_fo < b->bm_bits) {
+			unsigned long offset;
+			bit_offset = bm_fo & ~BPP_MASK; /* bit offset of the page */
+			offset = bit_offset >> LN2_BPL;    /* word offset of the page */
+			p_addr = __bm_map_paddr(b, offset, km);
+
+			if (find_zero_bit)
+				i = find_next_zero_bit(p_addr, PAGE_SIZE*8, bm_fo & BPP_MASK);
+			else
+				i = find_next_bit(p_addr, PAGE_SIZE*8, bm_fo & BPP_MASK);
+
+			__bm_unmap(p_addr, km);
+			if (i < PAGE_SIZE*8) {
+				i = bit_offset + i;
+				if (i >= b->bm_bits)
+					break;
+				goto found;
+			}
+			bm_fo = bit_offset + PAGE_SIZE*8;
+		}
+		i = -1UL;
+	}
+ found:
+	return i;
+}
+
+static unsigned long bm_find_next(struct drbd_conf *mdev,
+	unsigned long bm_fo, const int find_zero_bit)
+{
+	struct drbd_bitmap *b = mdev->bitmap;
+	unsigned long i = -1UL;
+
+	ERR_IF(!b) return i;
+	ERR_IF(!b->bm_pages) return i;
+
+	spin_lock_irq(&b->bm_lock);
+	if (bm_is_locked(b))
+		bm_print_lock_info(mdev);
+
+	i = __bm_find_next(mdev, bm_fo, find_zero_bit, KM_IRQ1);
+
+	spin_unlock_irq(&b->bm_lock);
+	return i;
+}
+
+unsigned long drbd_bm_find_next(struct drbd_conf *mdev, unsigned long bm_fo)
+{
+	return bm_find_next(mdev, bm_fo, 0);
+}
+
+#if 0
+/* not yet needed for anything. */
+unsigned long drbd_bm_find_next_zero(struct drbd_conf *mdev, unsigned long bm_fo)
+{
+	return bm_find_next(mdev, bm_fo, 1);
+}
+#endif
+
+/* does not spin_lock_irqsave.
+ * you must take drbd_bm_lock() first */
+unsigned long _drbd_bm_find_next(struct drbd_conf *mdev, unsigned long bm_fo)
+{
+	/* WARN_ON(!bm_is_locked(mdev)); */
+	return __bm_find_next(mdev, bm_fo, 0, KM_USER1);
+}
+
+unsigned long _drbd_bm_find_next_zero(struct drbd_conf *mdev, unsigned long bm_fo)
+{
+	/* WARN_ON(!bm_is_locked(mdev)); */
+	return __bm_find_next(mdev, bm_fo, 1, KM_USER1);
+}
+
+/* returns number of bits actually changed.
+ * for val != 0, we change 0 -> 1, return code positive
+ * for val == 0, we change 1 -> 0, return code negative
+ * wants bitnr, not sector.
+ * expected to be called for only a few bits (e - s about BITS_PER_LONG).
+ * Must hold bitmap lock already. */
+int __bm_change_bits_to(struct drbd_conf *mdev, const unsigned long s,
+	unsigned long e, int val, const enum km_type km)
+{
+	struct drbd_bitmap *b = mdev->bitmap;
+	unsigned long *p_addr = NULL;
+	unsigned long bitnr;
+	unsigned long last_page_nr = -1UL;
+	int c = 0;
+
+	if (e >= b->bm_bits) {
+		dev_err(DEV, "ASSERT FAILED: bit_s=%lu bit_e=%lu bm_bits=%lu\n",
+				s, e, b->bm_bits);
+		e = b->bm_bits ? b->bm_bits -1 : 0;
+	}
+	for (bitnr = s; bitnr <= e; bitnr++) {
+		unsigned long offset = bitnr>>LN2_BPL;
+		unsigned long page_nr = offset >> (PAGE_SHIFT - LN2_BPL + 3);
+		if (page_nr != last_page_nr) {
+			if (p_addr)
+				__bm_unmap(p_addr, km);
+			p_addr = __bm_map_paddr(b, offset, km);
+			last_page_nr = page_nr;
+		}
+		if (val)
+			c += (0 == __test_and_set_bit(bitnr & BPP_MASK, p_addr));
+		else
+			c -= (0 != __test_and_clear_bit(bitnr & BPP_MASK, p_addr));
+	}
+	if (p_addr)
+		__bm_unmap(p_addr, km);
+	b->bm_set += c;
+	return c;
+}
+
+/* returns number of bits actually changed.
+ * for val != 0, we change 0 -> 1, return code positive
+ * for val == 0, we change 1 -> 0, return code negative
+ * wants bitnr, not sector */
+int bm_change_bits_to(struct drbd_conf *mdev, const unsigned long s,
+	const unsigned long e, int val)
+{
+	unsigned long flags;
+	struct drbd_bitmap *b = mdev->bitmap;
+	int c = 0;
+
+	ERR_IF(!b) return 1;
+	ERR_IF(!b->bm_pages) return 0;
+
+	spin_lock_irqsave(&b->bm_lock, flags);
+	if (bm_is_locked(b))
+		bm_print_lock_info(mdev);
+
+	c = __bm_change_bits_to(mdev, s, e, val, KM_IRQ1);
+
+	spin_unlock_irqrestore(&b->bm_lock, flags);
+	return c;
+}
+
+/* returns number of bits changed 0 -> 1 */
+int drbd_bm_set_bits(struct drbd_conf *mdev, const unsigned long s, const unsigned long e)
+{
+	return bm_change_bits_to(mdev, s, e, 1);
+}
+
+/* returns number of bits changed 1 -> 0 */
+int drbd_bm_clear_bits(struct drbd_conf *mdev, const unsigned long s, const unsigned long e)
+{
+	return -bm_change_bits_to(mdev, s, e, 0);
+}
+
+/* sets all bits in full words,
+ * from first_word up to, but not including, last_word */
+static inline void bm_set_full_words_within_one_page(struct drbd_bitmap *b,
+		int page_nr, int first_word, int last_word)
+{
+	int i;
+	int bits;
+	unsigned long *paddr = kmap_atomic(b->bm_pages[page_nr], KM_USER0);
+	for (i = first_word; i < last_word; i++) {
+		bits = hweight_long(paddr[i]);
+		paddr[i] = ~0UL;
+		b->bm_set += BITS_PER_LONG - bits;
+	}
+	kunmap_atomic(paddr, KM_USER0);
+}
+
+/* Same thing as drbd_bm_set_bits, but without taking the spin_lock_irqsave.
+ * You must first drbd_bm_lock().
+ * Can be called to set the whole bitmap in one go.
+ * Sets bits from s to e _inclusive_. */
+void _drbd_bm_set_bits(struct drbd_conf *mdev, const unsigned long s, const unsigned long e)
+{
+	/* First set_bit from the first bit (s)
+	 * up to the next long boundary (sl),
+	 * then assign full words up to the last long boundary (el),
+	 * then set_bit up to and including the last bit (e).
+	 *
+	 * Do not use memset, because we must account for changes,
+	 * so we need to loop over the words with hweight() anyways.
+	 */
+	unsigned long sl = ALIGN(s,BITS_PER_LONG);
+	unsigned long el = (e+1) & ~((unsigned long)BITS_PER_LONG-1);
+	int first_page;
+	int last_page;
+	int page_nr;
+	int first_word;
+	int last_word;
+
+	if (e - s <= 3*BITS_PER_LONG) {
+		/* don't bother; el and sl may even be wrong. */
+		__bm_change_bits_to(mdev, s, e, 1, KM_USER0);
+		return;
+	}
+
+	/* difference is large enough that we can trust sl and el */
+
+	/* bits filling the current long */
+	if (sl)
+		__bm_change_bits_to(mdev, s, sl-1, 1, KM_USER0);
+
+	first_page = sl >> (3 + PAGE_SHIFT);
+	last_page = el >> (3 + PAGE_SHIFT);
+
+	/* MLPP: modulo longs per page */
+	/* LWPP: long words per page */
+	first_word = MLPP(sl >> LN2_BPL);
+	last_word = LWPP;
+
+	/* first and full pages, unless first page == last page */
+	for (page_nr = first_page; page_nr < last_page; page_nr++) {
+		bm_set_full_words_within_one_page(mdev->bitmap, page_nr, first_word, last_word);
+		cond_resched();
+		first_word = 0;
+	}
+
+	/* last page (respectively only page, for first page == last page) */
+	last_word = MLPP(el >> LN2_BPL);
+	bm_set_full_words_within_one_page(mdev->bitmap, last_page, first_word, last_word);
+
+	/* possibly trailing bits.
+	 * example: (e & 63) == 63, el will be e+1.
+	 * if that even was the very last bit,
+	 * it would trigger an assert in __bm_change_bits_to()
+	 */
+	if (el <= e)
+		__bm_change_bits_to(mdev, el, e, 1, KM_USER0);
+}
+
+/* returns bit state
+ * wants bitnr, NOT sector.
+ * inherently racy... area needs to be locked by means of {al,rs}_lru
+ *  1 ... bit set
+ *  0 ... bit not set
+ * -1 ... first out of bounds access, stop testing for bits!
+ */
+int drbd_bm_test_bit(struct drbd_conf *mdev, const unsigned long bitnr)
+{
+	unsigned long flags;
+	struct drbd_bitmap *b = mdev->bitmap;
+	unsigned long *p_addr;
+	int i;
+
+	ERR_IF(!b) return 0;
+	ERR_IF(!b->bm_pages) return 0;
+
+	spin_lock_irqsave(&b->bm_lock, flags);
+	if (bm_is_locked(b))
+		bm_print_lock_info(mdev);
+	if (bitnr < b->bm_bits) {
+		unsigned long offset = bitnr>>LN2_BPL;
+		p_addr = bm_map_paddr(b, offset);
+		i = test_bit(bitnr & BPP_MASK, p_addr) ? 1 : 0;
+		bm_unmap(p_addr);
+	} else if (bitnr == b->bm_bits) {
+		i = -1;
+	} else { /* (bitnr > b->bm_bits) */
+		dev_err(DEV, "bitnr=%lu > bm_bits=%lu\n", bitnr, b->bm_bits);
+		i = 0;
+	}
+
+	spin_unlock_irqrestore(&b->bm_lock, flags);
+	return i;
+}
+
+/* returns number of bits set in the range [s, e] */
+int drbd_bm_count_bits(struct drbd_conf *mdev, const unsigned long s, const unsigned long e)
+{
+	unsigned long flags;
+	struct drbd_bitmap *b = mdev->bitmap;
+	unsigned long *p_addr = NULL, page_nr = -1;
+	unsigned long bitnr;
+	int c = 0;
+	size_t w;
+
+	/* If this is called without a bitmap, that is a bug.  But just to be
+	 * robust in case we screwed up elsewhere, in that case pretend there
+	 * was one dirty bit in the requested area, so we won't try to do a
+	 * local read there (no bitmap probably implies no disk) */
+	ERR_IF(!b) return 1;
+	ERR_IF(!b->bm_pages) return 1;
+
+	spin_lock_irqsave(&b->bm_lock, flags);
+	if (bm_is_locked(b))
+		bm_print_lock_info(mdev);
+	for (bitnr = s; bitnr <= e; bitnr++) {
+		w = bitnr >> LN2_BPL;
+		if (page_nr != w >> (PAGE_SHIFT - LN2_BPL + 3)) {
+			page_nr = w >> (PAGE_SHIFT - LN2_BPL + 3);
+			if (p_addr)
+				bm_unmap(p_addr);
+			p_addr = bm_map_paddr(b, w);
+		}
+		ERR_IF (bitnr >= b->bm_bits) {
+			dev_err(DEV, "bitnr=%lu bm_bits=%lu\n", bitnr, b->bm_bits);
+		} else {
+			c += (0 != test_bit(bitnr - (page_nr << (PAGE_SHIFT+3)), p_addr));
+		}
+	}
+	if (p_addr)
+		bm_unmap(p_addr);
+	spin_unlock_irqrestore(&b->bm_lock, flags);
+	return c;
+}
+
+
+/* inherently racy...
+ * return value may be already out-of-date when this function returns.
+ * but the general usage is that this is only use during a cstate when bits are
+ * only cleared, not set, and typically only care for the case when the return
+ * value is zero, or we already "locked" this "bitmap extent" by other means.
+ *
+ * enr is bm-extent number, since we chose to name one sector (512 bytes)
+ * worth of the bitmap a "bitmap extent".
+ *
+ * TODO
+ * I think since we use it like a reference count, we should use the real
+ * reference count of some bitmap extent element from some lru instead...
+ *
+ */
+int drbd_bm_e_weight(struct drbd_conf *mdev, unsigned long enr)
+{
+	struct drbd_bitmap *b = mdev->bitmap;
+	int count, s, e;
+	unsigned long flags;
+	unsigned long *p_addr, *bm;
+
+	ERR_IF(!b) return 0;
+	ERR_IF(!b->bm_pages) return 0;
+
+	spin_lock_irqsave(&b->bm_lock, flags);
+	if (bm_is_locked(b))
+		bm_print_lock_info(mdev);
+
+	s = S2W(enr);
+	e = min((size_t)S2W(enr+1), b->bm_words);
+	count = 0;
+	if (s < b->bm_words) {
+		int n = e-s;
+		p_addr = bm_map_paddr(b, s);
+		bm = p_addr + MLPP(s);
+		while (n--)
+			count += hweight_long(*bm++);
+		bm_unmap(p_addr);
+	} else {
+		dev_err(DEV, "start offset (%d) too large in drbd_bm_e_weight\n", s);
+	}
+	spin_unlock_irqrestore(&b->bm_lock, flags);
+	return count;
+}
+
+/* set all bits covered by the AL-extent al_enr */
+unsigned long drbd_bm_ALe_set_all(struct drbd_conf *mdev, unsigned long al_enr)
+{
+	struct drbd_bitmap *b = mdev->bitmap;
+	unsigned long *p_addr, *bm;
+	unsigned long weight;
+	int count, s, e, i, do_now;
+	ERR_IF(!b) return 0;
+	ERR_IF(!b->bm_pages) return 0;
+
+	spin_lock_irq(&b->bm_lock);
+	if (bm_is_locked(b))
+		bm_print_lock_info(mdev);
+	weight = b->bm_set;
+
+	s = al_enr * BM_WORDS_PER_AL_EXT;
+	e = min_t(size_t, s + BM_WORDS_PER_AL_EXT, b->bm_words);
+	/* assert that s and e are on the same page */
+	D_ASSERT((e-1) >> (PAGE_SHIFT - LN2_BPL + 3)
+	      ==  s    >> (PAGE_SHIFT - LN2_BPL + 3));
+	count = 0;
+	if (s < b->bm_words) {
+		i = do_now = e-s;
+		p_addr = bm_map_paddr(b, s);
+		bm = p_addr + MLPP(s);
+		while (i--) {
+			count += hweight_long(*bm);
+			*bm = -1UL;
+			bm++;
+		}
+		bm_unmap(p_addr);
+		b->bm_set += do_now*BITS_PER_LONG - count;
+		if (e == b->bm_words)
+			b->bm_set -= bm_clear_surplus(b);
+	} else {
+		dev_err(DEV, "start offset (%d) too large in drbd_bm_ALe_set_all\n", s);
+	}
+	weight = b->bm_set - weight;
+	spin_unlock_irq(&b->bm_lock);
+	return weight;
+}
diff --git a/drivers/block/drbd/drbd_int.h b/drivers/block/drbd/drbd_int.h
new file mode 100644
index 00000000000..8da602e010b
--- /dev/null
+++ b/drivers/block/drbd/drbd_int.h
@@ -0,0 +1,2258 @@
+/*
+  drbd_int.h
+
+  This file is part of DRBD by Philipp Reisner and Lars Ellenberg.
+
+  Copyright (C) 2001-2008, LINBIT Information Technologies GmbH.
+  Copyright (C) 1999-2008, Philipp Reisner <philipp.reisner@linbit.com>.
+  Copyright (C) 2002-2008, Lars Ellenberg <lars.ellenberg@linbit.com>.
+
+  drbd is free software; you can redistribute it and/or modify
+  it under the terms of the GNU General Public License as published by
+  the Free Software Foundation; either version 2, or (at your option)
+  any later version.
+
+  drbd is distributed in the hope that it will be useful,
+  but WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.	See the
+  GNU General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with drbd; see the file COPYING.  If not, write to
+  the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
+
+*/
+
+#ifndef _DRBD_INT_H
+#define _DRBD_INT_H
+
+#include <linux/compiler.h>
+#include <linux/types.h>
+#include <linux/version.h>
+#include <linux/list.h>
+#include <linux/sched.h>
+#include <linux/bitops.h>
+#include <linux/slab.h>
+#include <linux/crypto.h>
+#include <linux/tcp.h>
+#include <linux/mutex.h>
+#include <linux/major.h>
+#include <linux/blkdev.h>
+#include <linux/genhd.h>
+#include <net/tcp.h>
+#include <linux/lru_cache.h>
+
+#ifdef __CHECKER__
+# define __protected_by(x)       __attribute__((require_context(x,1,999,"rdwr")))
+# define __protected_read_by(x)  __attribute__((require_context(x,1,999,"read")))
+# define __protected_write_by(x) __attribute__((require_context(x,1,999,"write")))
+# define __must_hold(x)       __attribute__((context(x,1,1), require_context(x,1,999,"call")))
+#else
+# define __protected_by(x)
+# define __protected_read_by(x)
+# define __protected_write_by(x)
+# define __must_hold(x)
+#endif
+
+#define __no_warn(lock, stmt) do { __acquire(lock); stmt; __release(lock); } while (0)
+
+/* module parameter, defined in drbd_main.c */
+extern unsigned int minor_count;
+extern int disable_sendpage;
+extern int allow_oos;
+extern unsigned int cn_idx;
+
+#ifdef CONFIG_DRBD_FAULT_INJECTION
+extern int enable_faults;
+extern int fault_rate;
+extern int fault_devs;
+#endif
+
+extern char usermode_helper[];
+
+
+#ifndef TRUE
+#define TRUE 1
+#endif
+#ifndef FALSE
+#define FALSE 0
+#endif
+
+/* I don't remember why XCPU ...
+ * This is used to wake the asender,
+ * and to interrupt sending the sending task
+ * on disconnect.
+ */
+#define DRBD_SIG SIGXCPU
+
+/* This is used to stop/restart our threads.
+ * Cannot use SIGTERM nor SIGKILL, since these
+ * are sent out by init on runlevel changes
+ * I choose SIGHUP for now.
+ */
+#define DRBD_SIGKILL SIGHUP
+
+/* All EEs on the free list should have ID_VACANT (== 0)
+ * freshly allocated EEs get !ID_VACANT (== 1)
+ * so if it says "cannot dereference null pointer at adress 0x00000001",
+ * it is most likely one of these :( */
+
+#define ID_IN_SYNC      (4711ULL)
+#define ID_OUT_OF_SYNC  (4712ULL)
+
+#define ID_SYNCER (-1ULL)
+#define ID_VACANT 0
+#define is_syncer_block_id(id) ((id) == ID_SYNCER)
+
+struct drbd_conf;
+
+
+/* to shorten dev_warn(DEV, "msg"); and relatives statements */
+#define DEV (disk_to_dev(mdev->vdisk))
+
+#define D_ASSERT(exp)	if (!(exp)) \
+	 dev_err(DEV, "ASSERT( " #exp " ) in %s:%d\n", __FILE__, __LINE__)
+
+#define ERR_IF(exp) if (({				\
+	int _b = (exp) != 0;				\
+	if (_b) dev_err(DEV, "%s: (%s) in %s:%d\n",	\
+		__func__, #exp, __FILE__, __LINE__);	\
+	 _b;						\
+	}))
+
+/* Defines to control fault insertion */
+enum {
+	DRBD_FAULT_MD_WR = 0,	/* meta data write */
+	DRBD_FAULT_MD_RD = 1,	/*           read  */
+	DRBD_FAULT_RS_WR = 2,	/* resync          */
+	DRBD_FAULT_RS_RD = 3,
+	DRBD_FAULT_DT_WR = 4,	/* data            */
+	DRBD_FAULT_DT_RD = 5,
+	DRBD_FAULT_DT_RA = 6,	/* data read ahead */
+	DRBD_FAULT_BM_ALLOC = 7,	/* bitmap allocation */
+	DRBD_FAULT_AL_EE = 8,	/* alloc ee */
+
+	DRBD_FAULT_MAX,
+};
+
+extern void trace_drbd_resync(struct drbd_conf *mdev, int level, const char *fmt, ...);
+
+#ifdef CONFIG_DRBD_FAULT_INJECTION
+extern unsigned int
+_drbd_insert_fault(struct drbd_conf *mdev, unsigned int type);
+static inline int
+drbd_insert_fault(struct drbd_conf *mdev, unsigned int type) {
+	return fault_rate &&
+		(enable_faults & (1<<type)) &&
+		_drbd_insert_fault(mdev, type);
+}
+#define FAULT_ACTIVE(_m, _t) (drbd_insert_fault((_m), (_t)))
+
+#else
+#define FAULT_ACTIVE(_m, _t) (0)
+#endif
+
+/* integer division, round _UP_ to the next integer */
+#define div_ceil(A, B) ((A)/(B) + ((A)%(B) ? 1 : 0))
+/* usual integer division */
+#define div_floor(A, B) ((A)/(B))
+
+/* drbd_meta-data.c (still in drbd_main.c) */
+/* 4th incarnation of the disk layout. */
+#define DRBD_MD_MAGIC (DRBD_MAGIC+4)
+
+extern struct drbd_conf **minor_table;
+extern struct ratelimit_state drbd_ratelimit_state;
+
+/* on the wire */
+enum drbd_packets {
+	/* receiver (data socket) */
+	P_DATA		      = 0x00,
+	P_DATA_REPLY	      = 0x01, /* Response to P_DATA_REQUEST */
+	P_RS_DATA_REPLY	      = 0x02, /* Response to P_RS_DATA_REQUEST */
+	P_BARRIER	      = 0x03,
+	P_BITMAP	      = 0x04,
+	P_BECOME_SYNC_TARGET  = 0x05,
+	P_BECOME_SYNC_SOURCE  = 0x06,
+	P_UNPLUG_REMOTE	      = 0x07, /* Used at various times to hint the peer */
+	P_DATA_REQUEST	      = 0x08, /* Used to ask for a data block */
+	P_RS_DATA_REQUEST     = 0x09, /* Used to ask for a data block for resync */
+	P_SYNC_PARAM	      = 0x0a,
+	P_PROTOCOL	      = 0x0b,
+	P_UUIDS		      = 0x0c,
+	P_SIZES		      = 0x0d,
+	P_STATE		      = 0x0e,
+	P_SYNC_UUID	      = 0x0f,
+	P_AUTH_CHALLENGE      = 0x10,
+	P_AUTH_RESPONSE	      = 0x11,
+	P_STATE_CHG_REQ	      = 0x12,
+
+	/* asender (meta socket */
+	P_PING		      = 0x13,
+	P_PING_ACK	      = 0x14,
+	P_RECV_ACK	      = 0x15, /* Used in protocol B */
+	P_WRITE_ACK	      = 0x16, /* Used in protocol C */
+	P_RS_WRITE_ACK	      = 0x17, /* Is a P_WRITE_ACK, additionally call set_in_sync(). */
+	P_DISCARD_ACK	      = 0x18, /* Used in proto C, two-primaries conflict detection */
+	P_NEG_ACK	      = 0x19, /* Sent if local disk is unusable */
+	P_NEG_DREPLY	      = 0x1a, /* Local disk is broken... */
+	P_NEG_RS_DREPLY	      = 0x1b, /* Local disk is broken... */
+	P_BARRIER_ACK	      = 0x1c,
+	P_STATE_CHG_REPLY     = 0x1d,
+
+	/* "new" commands, no longer fitting into the ordering scheme above */
+
+	P_OV_REQUEST	      = 0x1e, /* data socket */
+	P_OV_REPLY	      = 0x1f,
+	P_OV_RESULT	      = 0x20, /* meta socket */
+	P_CSUM_RS_REQUEST     = 0x21, /* data socket */
+	P_RS_IS_IN_SYNC	      = 0x22, /* meta socket */
+	P_SYNC_PARAM89	      = 0x23, /* data socket, protocol version 89 replacement for P_SYNC_PARAM */
+	P_COMPRESSED_BITMAP   = 0x24, /* compressed or otherwise encoded bitmap transfer */
+
+	P_MAX_CMD	      = 0x25,
+	P_MAY_IGNORE	      = 0x100, /* Flag to test if (cmd > P_MAY_IGNORE) ... */
+	P_MAX_OPT_CMD	      = 0x101,
+
+	/* special command ids for handshake */
+
+	P_HAND_SHAKE_M	      = 0xfff1, /* First Packet on the MetaSock */
+	P_HAND_SHAKE_S	      = 0xfff2, /* First Packet on the Socket */
+
+	P_HAND_SHAKE	      = 0xfffe	/* FIXED for the next century! */
+};
+
+static inline const char *cmdname(enum drbd_packets cmd)
+{
+	/* THINK may need to become several global tables
+	 * when we want to support more than
+	 * one PRO_VERSION */
+	static const char *cmdnames[] = {
+		[P_DATA]	        = "Data",
+		[P_DATA_REPLY]	        = "DataReply",
+		[P_RS_DATA_REPLY]	= "RSDataReply",
+		[P_BARRIER]	        = "Barrier",
+		[P_BITMAP]	        = "ReportBitMap",
+		[P_BECOME_SYNC_TARGET]  = "BecomeSyncTarget",
+		[P_BECOME_SYNC_SOURCE]  = "BecomeSyncSource",
+		[P_UNPLUG_REMOTE]	= "UnplugRemote",
+		[P_DATA_REQUEST]	= "DataRequest",
+		[P_RS_DATA_REQUEST]     = "RSDataRequest",
+		[P_SYNC_PARAM]	        = "SyncParam",
+		[P_SYNC_PARAM89]	= "SyncParam89",
+		[P_PROTOCOL]            = "ReportProtocol",
+		[P_UUIDS]	        = "ReportUUIDs",
+		[P_SIZES]	        = "ReportSizes",
+		[P_STATE]	        = "ReportState",
+		[P_SYNC_UUID]           = "ReportSyncUUID",
+		[P_AUTH_CHALLENGE]      = "AuthChallenge",
+		[P_AUTH_RESPONSE]	= "AuthResponse",
+		[P_PING]		= "Ping",
+		[P_PING_ACK]	        = "PingAck",
+		[P_RECV_ACK]	        = "RecvAck",
+		[P_WRITE_ACK]	        = "WriteAck",
+		[P_RS_WRITE_ACK]	= "RSWriteAck",
+		[P_DISCARD_ACK]	        = "DiscardAck",
+		[P_NEG_ACK]	        = "NegAck",
+		[P_NEG_DREPLY]	        = "NegDReply",
+		[P_NEG_RS_DREPLY]	= "NegRSDReply",
+		[P_BARRIER_ACK]	        = "BarrierAck",
+		[P_STATE_CHG_REQ]       = "StateChgRequest",
+		[P_STATE_CHG_REPLY]     = "StateChgReply",
+		[P_OV_REQUEST]          = "OVRequest",
+		[P_OV_REPLY]            = "OVReply",
+		[P_OV_RESULT]           = "OVResult",
+		[P_MAX_CMD]	        = NULL,
+	};
+
+	if (cmd == P_HAND_SHAKE_M)
+		return "HandShakeM";
+	if (cmd == P_HAND_SHAKE_S)
+		return "HandShakeS";
+	if (cmd == P_HAND_SHAKE)
+		return "HandShake";
+	if (cmd >= P_MAX_CMD)
+		return "Unknown";
+	return cmdnames[cmd];
+}
+
+/* for sending/receiving the bitmap,
+ * possibly in some encoding scheme */
+struct bm_xfer_ctx {
+	/* "const"
+	 * stores total bits and long words
+	 * of the bitmap, so we don't need to
+	 * call the accessor functions over and again. */
+	unsigned long bm_bits;
+	unsigned long bm_words;
+	/* during xfer, current position within the bitmap */
+	unsigned long bit_offset;
+	unsigned long word_offset;
+
+	/* statistics; index: (h->command == P_BITMAP) */
+	unsigned packets[2];
+	unsigned bytes[2];
+};
+
+extern void INFO_bm_xfer_stats(struct drbd_conf *mdev,
+		const char *direction, struct bm_xfer_ctx *c);
+
+static inline void bm_xfer_ctx_bit_to_word_offset(struct bm_xfer_ctx *c)
+{
+	/* word_offset counts "native long words" (32 or 64 bit),
+	 * aligned at 64 bit.
+	 * Encoded packet may end at an unaligned bit offset.
+	 * In case a fallback clear text packet is transmitted in
+	 * between, we adjust this offset back to the last 64bit
+	 * aligned "native long word", which makes coding and decoding
+	 * the plain text bitmap much more convenient.  */
+#if BITS_PER_LONG == 64
+	c->word_offset = c->bit_offset >> 6;
+#elif BITS_PER_LONG == 32
+	c->word_offset = c->bit_offset >> 5;
+	c->word_offset &= ~(1UL);
+#else
+# error "unsupported BITS_PER_LONG"
+#endif
+}
+
+#ifndef __packed
+#define __packed __attribute__((packed))
+#endif
+
+/* This is the layout for a packet on the wire.
+ * The byteorder is the network byte order.
+ *     (except block_id and barrier fields.
+ *	these are pointers to local structs
+ *	and have no relevance for the partner,
+ *	which just echoes them as received.)
+ *
+ * NOTE that the payload starts at a long aligned offset,
+ * regardless of 32 or 64 bit arch!
+ */
+struct p_header {
+	u32	  magic;
+	u16	  command;
+	u16	  length;	/* bytes of data after this header */
+	u8	  payload[0];
+} __packed;
+/* 8 bytes. packet FIXED for the next century! */
+
+/*
+ * short commands, packets without payload, plain p_header:
+ *   P_PING
+ *   P_PING_ACK
+ *   P_BECOME_SYNC_TARGET
+ *   P_BECOME_SYNC_SOURCE
+ *   P_UNPLUG_REMOTE
+ */
+
+/*
+ * commands with out-of-struct payload:
+ *   P_BITMAP    (no additional fields)
+ *   P_DATA, P_DATA_REPLY (see p_data)
+ *   P_COMPRESSED_BITMAP (see receive_compressed_bitmap)
+ */
+
+/* these defines must not be changed without changing the protocol version */
+#define DP_HARDBARRIER	      1
+#define DP_RW_SYNC	      2
+#define DP_MAY_SET_IN_SYNC    4
+
+struct p_data {
+	struct p_header head;
+	u64	    sector;    /* 64 bits sector number */
+	u64	    block_id;  /* to identify the request in protocol B&C */
+	u32	    seq_num;
+	u32	    dp_flags;
+} __packed;
+
+/*
+ * commands which share a struct:
+ *  p_block_ack:
+ *   P_RECV_ACK (proto B), P_WRITE_ACK (proto C),
+ *   P_DISCARD_ACK (proto C, two-primaries conflict detection)
+ *  p_block_req:
+ *   P_DATA_REQUEST, P_RS_DATA_REQUEST
+ */
+struct p_block_ack {
+	struct p_header head;
+	u64	    sector;
+	u64	    block_id;
+	u32	    blksize;
+	u32	    seq_num;
+} __packed;
+
+
+struct p_block_req {
+	struct p_header head;
+	u64 sector;
+	u64 block_id;
+	u32 blksize;
+	u32 pad;	/* to multiple of 8 Byte */
+} __packed;
+
+/*
+ * commands with their own struct for additional fields:
+ *   P_HAND_SHAKE
+ *   P_BARRIER
+ *   P_BARRIER_ACK
+ *   P_SYNC_PARAM
+ *   ReportParams
+ */
+
+struct p_handshake {
+	struct p_header head;	/* 8 bytes */
+	u32 protocol_min;
+	u32 feature_flags;
+	u32 protocol_max;
+
+	/* should be more than enough for future enhancements
+	 * for now, feature_flags and the reserverd array shall be zero.
+	 */
+
+	u32 _pad;
+	u64 reserverd[7];
+} __packed;
+/* 80 bytes, FIXED for the next century */
+
+struct p_barrier {
+	struct p_header head;
+	u32 barrier;	/* barrier number _handle_ only */
+	u32 pad;	/* to multiple of 8 Byte */
+} __packed;
+
+struct p_barrier_ack {
+	struct p_header head;
+	u32 barrier;
+	u32 set_size;
+} __packed;
+
+struct p_rs_param {
+	struct p_header head;
+	u32 rate;
+
+	      /* Since protocol version 88 and higher. */
+	char verify_alg[0];
+} __packed;
+
+struct p_rs_param_89 {
+	struct p_header head;
+	u32 rate;
+        /* protocol version 89: */
+	char verify_alg[SHARED_SECRET_MAX];
+	char csums_alg[SHARED_SECRET_MAX];
+} __packed;
+
+struct p_protocol {
+	struct p_header head;
+	u32 protocol;
+	u32 after_sb_0p;
+	u32 after_sb_1p;
+	u32 after_sb_2p;
+	u32 want_lose;
+	u32 two_primaries;
+
+              /* Since protocol version 87 and higher. */
+	char integrity_alg[0];
+
+} __packed;
+
+struct p_uuids {
+	struct p_header head;
+	u64 uuid[UI_EXTENDED_SIZE];
+} __packed;
+
+struct p_rs_uuid {
+	struct p_header head;
+	u64	    uuid;
+} __packed;
+
+struct p_sizes {
+	struct p_header head;
+	u64	    d_size;  /* size of disk */
+	u64	    u_size;  /* user requested size */
+	u64	    c_size;  /* current exported size */
+	u32	    max_segment_size;  /* Maximal size of a BIO */
+	u32	    queue_order_type;
+} __packed;
+
+struct p_state {
+	struct p_header head;
+	u32	    state;
+} __packed;
+
+struct p_req_state {
+	struct p_header head;
+	u32	    mask;
+	u32	    val;
+} __packed;
+
+struct p_req_state_reply {
+	struct p_header head;
+	u32	    retcode;
+} __packed;
+
+struct p_drbd06_param {
+	u64	  size;
+	u32	  state;
+	u32	  blksize;
+	u32	  protocol;
+	u32	  version;
+	u32	  gen_cnt[5];
+	u32	  bit_map_gen[5];
+} __packed;
+
+struct p_discard {
+	struct p_header head;
+	u64	    block_id;
+	u32	    seq_num;
+	u32	    pad;
+} __packed;
+
+/* Valid values for the encoding field.
+ * Bump proto version when changing this. */
+enum drbd_bitmap_code {
+	/* RLE_VLI_Bytes = 0,
+	 * and other bit variants had been defined during
+	 * algorithm evaluation. */
+	RLE_VLI_Bits = 2,
+};
+
+struct p_compressed_bm {
+	struct p_header head;
+	/* (encoding & 0x0f): actual encoding, see enum drbd_bitmap_code
+	 * (encoding & 0x80): polarity (set/unset) of first runlength
+	 * ((encoding >> 4) & 0x07): pad_bits, number of trailing zero bits
+	 * used to pad up to head.length bytes
+	 */
+	u8 encoding;
+
+	u8 code[0];
+} __packed;
+
+/* DCBP: Drbd Compressed Bitmap Packet ... */
+static inline enum drbd_bitmap_code
+DCBP_get_code(struct p_compressed_bm *p)
+{
+	return (enum drbd_bitmap_code)(p->encoding & 0x0f);
+}
+
+static inline void
+DCBP_set_code(struct p_compressed_bm *p, enum drbd_bitmap_code code)
+{
+	BUG_ON(code & ~0xf);
+	p->encoding = (p->encoding & ~0xf) | code;
+}
+
+static inline int
+DCBP_get_start(struct p_compressed_bm *p)
+{
+	return (p->encoding & 0x80) != 0;
+}
+
+static inline void
+DCBP_set_start(struct p_compressed_bm *p, int set)
+{
+	p->encoding = (p->encoding & ~0x80) | (set ? 0x80 : 0);
+}
+
+static inline int
+DCBP_get_pad_bits(struct p_compressed_bm *p)
+{
+	return (p->encoding >> 4) & 0x7;
+}
+
+static inline void
+DCBP_set_pad_bits(struct p_compressed_bm *p, int n)
+{
+	BUG_ON(n & ~0x7);
+	p->encoding = (p->encoding & (~0x7 << 4)) | (n << 4);
+}
+
+/* one bitmap packet, including the p_header,
+ * should fit within one _architecture independend_ page.
+ * so we need to use the fixed size 4KiB page size
+ * most architechtures have used for a long time.
+ */
+#define BM_PACKET_PAYLOAD_BYTES (4096 - sizeof(struct p_header))
+#define BM_PACKET_WORDS (BM_PACKET_PAYLOAD_BYTES/sizeof(long))
+#define BM_PACKET_VLI_BYTES_MAX (4096 - sizeof(struct p_compressed_bm))
+#if (PAGE_SIZE < 4096)
+/* drbd_send_bitmap / receive_bitmap would break horribly */
+#error "PAGE_SIZE too small"
+#endif
+
+union p_polymorph {
+        struct p_header          header;
+        struct p_handshake       handshake;
+        struct p_data            data;
+        struct p_block_ack       block_ack;
+        struct p_barrier         barrier;
+        struct p_barrier_ack     barrier_ack;
+        struct p_rs_param_89     rs_param_89;
+        struct p_protocol        protocol;
+        struct p_sizes           sizes;
+        struct p_uuids           uuids;
+        struct p_state           state;
+        struct p_req_state       req_state;
+        struct p_req_state_reply req_state_reply;
+        struct p_block_req       block_req;
+} __packed;
+
+/**********************************************************************/
+enum drbd_thread_state {
+	None,
+	Running,
+	Exiting,
+	Restarting
+};
+
+struct drbd_thread {
+	spinlock_t t_lock;
+	struct task_struct *task;
+	struct completion stop;
+	enum drbd_thread_state t_state;
+	int (*function) (struct drbd_thread *);
+	struct drbd_conf *mdev;
+	int reset_cpu_mask;
+};
+
+static inline enum drbd_thread_state get_t_state(struct drbd_thread *thi)
+{
+	/* THINK testing the t_state seems to be uncritical in all cases
+	 * (but thread_{start,stop}), so we can read it *without* the lock.
+	 *	--lge */
+
+	smp_rmb();
+	return thi->t_state;
+}
+
+
+/*
+ * Having this as the first member of a struct provides sort of "inheritance".
+ * "derived" structs can be "drbd_queue_work()"ed.
+ * The callback should know and cast back to the descendant struct.
+ * drbd_request and drbd_epoch_entry are descendants of drbd_work.
+ */
+struct drbd_work;
+typedef int (*drbd_work_cb)(struct drbd_conf *, struct drbd_work *, int cancel);
+struct drbd_work {
+	struct list_head list;
+	drbd_work_cb cb;
+};
+
+struct drbd_tl_epoch;
+struct drbd_request {
+	struct drbd_work w;
+	struct drbd_conf *mdev;
+
+	/* if local IO is not allowed, will be NULL.
+	 * if local IO _is_ allowed, holds the locally submitted bio clone,
+	 * or, after local IO completion, the ERR_PTR(error).
+	 * see drbd_endio_pri(). */
+	struct bio *private_bio;
+
+	struct hlist_node colision;
+	sector_t sector;
+	unsigned int size;
+	unsigned int epoch; /* barrier_nr */
+
+	/* barrier_nr: used to check on "completion" whether this req was in
+	 * the current epoch, and we therefore have to close it,
+	 * starting a new epoch...
+	 */
+
+	/* up to here, the struct layout is identical to drbd_epoch_entry;
+	 * we might be able to use that to our advantage...  */
+
+	struct list_head tl_requests; /* ring list in the transfer log */
+	struct bio *master_bio;       /* master bio pointer */
+	unsigned long rq_state; /* see comments above _req_mod() */
+	int seq_num;
+	unsigned long start_time;
+};
+
+struct drbd_tl_epoch {
+	struct drbd_work w;
+	struct list_head requests; /* requests before */
+	struct drbd_tl_epoch *next; /* pointer to the next barrier */
+	unsigned int br_number;  /* the barriers identifier. */
+	int n_req;	/* number of requests attached before this barrier */
+};
+
+struct drbd_request;
+
+/* These Tl_epoch_entries may be in one of 6 lists:
+   active_ee .. data packet being written
+   sync_ee   .. syncer block being written
+   done_ee   .. block written, need to send P_WRITE_ACK
+   read_ee   .. [RS]P_DATA_REQUEST being read
+*/
+
+struct drbd_epoch {
+	struct list_head list;
+	unsigned int barrier_nr;
+	atomic_t epoch_size; /* increased on every request added. */
+	atomic_t active;     /* increased on every req. added, and dec on every finished. */
+	unsigned long flags;
+};
+
+/* drbd_epoch flag bits */
+enum {
+	DE_BARRIER_IN_NEXT_EPOCH_ISSUED,
+	DE_BARRIER_IN_NEXT_EPOCH_DONE,
+	DE_CONTAINS_A_BARRIER,
+	DE_HAVE_BARRIER_NUMBER,
+	DE_IS_FINISHING,
+};
+
+enum epoch_event {
+	EV_PUT,
+	EV_GOT_BARRIER_NR,
+	EV_BARRIER_DONE,
+	EV_BECAME_LAST,
+	EV_TRACE_FLUSH,       /* TRACE_ are not real events, only used for tracing */
+	EV_TRACE_ADD_BARRIER, /* Doing the first write as a barrier write */
+	EV_TRACE_SETTING_BI,  /* Barrier is expressed with the first write of the next epoch */
+	EV_TRACE_ALLOC,
+	EV_TRACE_FREE,
+	EV_CLEANUP = 32, /* used as flag */
+};
+
+struct drbd_epoch_entry {
+	struct drbd_work    w;
+	struct drbd_conf *mdev;
+	struct bio *private_bio;
+	struct hlist_node colision;
+	sector_t sector;
+	unsigned int size;
+	struct drbd_epoch *epoch;
+
+	/* up to here, the struct layout is identical to drbd_request;
+	 * we might be able to use that to our advantage...  */
+
+	unsigned int flags;
+	u64    block_id;
+};
+
+struct drbd_wq_barrier {
+	struct drbd_work w;
+	struct completion done;
+};
+
+struct digest_info {
+	int digest_size;
+	void *digest;
+};
+
+/* ee flag bits */
+enum {
+	__EE_CALL_AL_COMPLETE_IO,
+	__EE_CONFLICT_PENDING,
+	__EE_MAY_SET_IN_SYNC,
+	__EE_IS_BARRIER,
+};
+#define EE_CALL_AL_COMPLETE_IO (1<<__EE_CALL_AL_COMPLETE_IO)
+#define EE_CONFLICT_PENDING    (1<<__EE_CONFLICT_PENDING)
+#define EE_MAY_SET_IN_SYNC     (1<<__EE_MAY_SET_IN_SYNC)
+#define EE_IS_BARRIER          (1<<__EE_IS_BARRIER)
+
+/* global flag bits */
+enum {
+	CREATE_BARRIER,		/* next P_DATA is preceeded by a P_BARRIER */
+	SIGNAL_ASENDER,		/* whether asender wants to be interrupted */
+	SEND_PING,		/* whether asender should send a ping asap */
+
+	STOP_SYNC_TIMER,	/* tell timer to cancel itself */
+	UNPLUG_QUEUED,		/* only relevant with kernel 2.4 */
+	UNPLUG_REMOTE,		/* sending a "UnplugRemote" could help */
+	MD_DIRTY,		/* current uuids and flags not yet on disk */
+	DISCARD_CONCURRENT,	/* Set on one node, cleared on the peer! */
+	USE_DEGR_WFC_T,		/* degr-wfc-timeout instead of wfc-timeout. */
+	CLUSTER_ST_CHANGE,	/* Cluster wide state change going on... */
+	CL_ST_CHG_SUCCESS,
+	CL_ST_CHG_FAIL,
+	CRASHED_PRIMARY,	/* This node was a crashed primary.
+				 * Gets cleared when the state.conn
+				 * goes into C_CONNECTED state. */
+	WRITE_BM_AFTER_RESYNC,	/* A kmalloc() during resync failed */
+	NO_BARRIER_SUPP,	/* underlying block device doesn't implement barriers */
+	CONSIDER_RESYNC,
+
+	MD_NO_BARRIER,		/* meta data device does not support barriers,
+				   so don't even try */
+	SUSPEND_IO,		/* suspend application io */
+	BITMAP_IO,		/* suspend application io;
+				   once no more io in flight, start bitmap io */
+	BITMAP_IO_QUEUED,       /* Started bitmap IO */
+	RESYNC_AFTER_NEG,       /* Resync after online grow after the attach&negotiate finished. */
+	NET_CONGESTED,		/* The data socket is congested */
+
+	CONFIG_PENDING,		/* serialization of (re)configuration requests.
+				 * if set, also prevents the device from dying */
+	DEVICE_DYING,		/* device became unconfigured,
+				 * but worker thread is still handling the cleanup.
+				 * reconfiguring (nl_disk_conf, nl_net_conf) is dissalowed,
+				 * while this is set. */
+	RESIZE_PENDING,		/* Size change detected locally, waiting for the response from
+				 * the peer, if it changed there as well. */
+};
+
+struct drbd_bitmap; /* opaque for drbd_conf */
+
+/* TODO sort members for performance
+ * MAYBE group them further */
+
+/* THINK maybe we actually want to use the default "event/%s" worker threads
+ * or similar in linux 2.6, which uses per cpu data and threads.
+ *
+ * To be general, this might need a spin_lock member.
+ * For now, please use the mdev->req_lock to protect list_head,
+ * see drbd_queue_work below.
+ */
+struct drbd_work_queue {
+	struct list_head q;
+	struct semaphore s; /* producers up it, worker down()s it */
+	spinlock_t q_lock;  /* to protect the list. */
+};
+
+struct drbd_socket {
+	struct drbd_work_queue work;
+	struct mutex mutex;
+	struct socket    *socket;
+	/* this way we get our
+	 * send/receive buffers off the stack */
+	union p_polymorph sbuf;
+	union p_polymorph rbuf;
+};
+
+struct drbd_md {
+	u64 md_offset;		/* sector offset to 'super' block */
+
+	u64 la_size_sect;	/* last agreed size, unit sectors */
+	u64 uuid[UI_SIZE];
+	u64 device_uuid;
+	u32 flags;
+	u32 md_size_sect;
+
+	s32 al_offset;	/* signed relative sector offset to al area */
+	s32 bm_offset;	/* signed relative sector offset to bitmap */
+
+	/* u32 al_nr_extents;	   important for restoring the AL
+	 * is stored into  sync_conf.al_extents, which in turn
+	 * gets applied to act_log->nr_elements
+	 */
+};
+
+/* for sync_conf and other types... */
+#define NL_PACKET(name, number, fields) struct name { fields };
+#define NL_INTEGER(pn,pr,member) int member;
+#define NL_INT64(pn,pr,member) __u64 member;
+#define NL_BIT(pn,pr,member)   unsigned member:1;
+#define NL_STRING(pn,pr,member,len) unsigned char member[len]; int member ## _len;
+#include "linux/drbd_nl.h"
+
+struct drbd_backing_dev {
+	struct block_device *backing_bdev;
+	struct block_device *md_bdev;
+	struct file *lo_file;
+	struct file *md_file;
+	struct drbd_md md;
+	struct disk_conf dc; /* The user provided config... */
+	sector_t known_size; /* last known size of that backing device */
+};
+
+struct drbd_md_io {
+	struct drbd_conf *mdev;
+	struct completion event;
+	int error;
+};
+
+struct bm_io_work {
+	struct drbd_work w;
+	char *why;
+	int (*io_fn)(struct drbd_conf *mdev);
+	void (*done)(struct drbd_conf *mdev, int rv);
+};
+
+enum write_ordering_e {
+	WO_none,
+	WO_drain_io,
+	WO_bdev_flush,
+	WO_bio_barrier
+};
+
+struct drbd_conf {
+	/* things that are stored as / read from meta data on disk */
+	unsigned long flags;
+
+	/* configured by drbdsetup */
+	struct net_conf *net_conf; /* protected by get_net_conf() and put_net_conf() */
+	struct syncer_conf sync_conf;
+	struct drbd_backing_dev *ldev __protected_by(local);
+
+	sector_t p_size;     /* partner's disk size */
+	struct request_queue *rq_queue;
+	struct block_device *this_bdev;
+	struct gendisk	    *vdisk;
+
+	struct drbd_socket data; /* data/barrier/cstate/parameter packets */
+	struct drbd_socket meta; /* ping/ack (metadata) packets */
+	int agreed_pro_version;  /* actually used protocol version */
+	unsigned long last_received; /* in jiffies, either socket */
+	unsigned int ko_count;
+	struct drbd_work  resync_work,
+			  unplug_work,
+			  md_sync_work;
+	struct timer_list resync_timer;
+	struct timer_list md_sync_timer;
+
+	/* Used after attach while negotiating new disk state. */
+	union drbd_state new_state_tmp;
+
+	union drbd_state state;
+	wait_queue_head_t misc_wait;
+	wait_queue_head_t state_wait;  /* upon each state change. */
+	unsigned int send_cnt;
+	unsigned int recv_cnt;
+	unsigned int read_cnt;
+	unsigned int writ_cnt;
+	unsigned int al_writ_cnt;
+	unsigned int bm_writ_cnt;
+	atomic_t ap_bio_cnt;	 /* Requests we need to complete */
+	atomic_t ap_pending_cnt; /* AP data packets on the wire, ack expected */
+	atomic_t rs_pending_cnt; /* RS request/data packets on the wire */
+	atomic_t unacked_cnt;	 /* Need to send replys for */
+	atomic_t local_cnt;	 /* Waiting for local completion */
+	atomic_t net_cnt;	 /* Users of net_conf */
+	spinlock_t req_lock;
+	struct drbd_tl_epoch *unused_spare_tle; /* for pre-allocation */
+	struct drbd_tl_epoch *newest_tle;
+	struct drbd_tl_epoch *oldest_tle;
+	struct list_head out_of_sequence_requests;
+	struct hlist_head *tl_hash;
+	unsigned int tl_hash_s;
+
+	/* blocks to sync in this run [unit BM_BLOCK_SIZE] */
+	unsigned long rs_total;
+	/* number of sync IOs that failed in this run */
+	unsigned long rs_failed;
+	/* Syncer's start time [unit jiffies] */
+	unsigned long rs_start;
+	/* cumulated time in PausedSyncX state [unit jiffies] */
+	unsigned long rs_paused;
+	/* block not up-to-date at mark [unit BM_BLOCK_SIZE] */
+	unsigned long rs_mark_left;
+	/* marks's time [unit jiffies] */
+	unsigned long rs_mark_time;
+	/* skipped because csum was equeal [unit BM_BLOCK_SIZE] */
+	unsigned long rs_same_csum;
+
+	/* where does the admin want us to start? (sector) */
+	sector_t ov_start_sector;
+	/* where are we now? (sector) */
+	sector_t ov_position;
+	/* Start sector of out of sync range (to merge printk reporting). */
+	sector_t ov_last_oos_start;
+	/* size of out-of-sync range in sectors. */
+	sector_t ov_last_oos_size;
+	unsigned long ov_left; /* in bits */
+	struct crypto_hash *csums_tfm;
+	struct crypto_hash *verify_tfm;
+
+	struct drbd_thread receiver;
+	struct drbd_thread worker;
+	struct drbd_thread asender;
+	struct drbd_bitmap *bitmap;
+	unsigned long bm_resync_fo; /* bit offset for drbd_bm_find_next */
+
+	/* Used to track operations of resync... */
+	struct lru_cache *resync;
+	/* Number of locked elements in resync LRU */
+	unsigned int resync_locked;
+	/* resync extent number waiting for application requests */
+	unsigned int resync_wenr;
+
+	int open_cnt;
+	u64 *p_uuid;
+	struct drbd_epoch *current_epoch;
+	spinlock_t epoch_lock;
+	unsigned int epochs;
+	enum write_ordering_e write_ordering;
+	struct list_head active_ee; /* IO in progress */
+	struct list_head sync_ee;   /* IO in progress */
+	struct list_head done_ee;   /* send ack */
+	struct list_head read_ee;   /* IO in progress */
+	struct list_head net_ee;    /* zero-copy network send in progress */
+	struct hlist_head *ee_hash; /* is proteced by req_lock! */
+	unsigned int ee_hash_s;
+
+	/* this one is protected by ee_lock, single thread */
+	struct drbd_epoch_entry *last_write_w_barrier;
+
+	int next_barrier_nr;
+	struct hlist_head *app_reads_hash; /* is proteced by req_lock */
+	struct list_head resync_reads;
+	atomic_t pp_in_use;
+	wait_queue_head_t ee_wait;
+	struct page *md_io_page;	/* one page buffer for md_io */
+	struct page *md_io_tmpp;	/* for logical_block_size != 512 */
+	struct mutex md_io_mutex;	/* protects the md_io_buffer */
+	spinlock_t al_lock;
+	wait_queue_head_t al_wait;
+	struct lru_cache *act_log;	/* activity log */
+	unsigned int al_tr_number;
+	int al_tr_cycle;
+	int al_tr_pos;   /* position of the next transaction in the journal */
+	struct crypto_hash *cram_hmac_tfm;
+	struct crypto_hash *integrity_w_tfm; /* to be used by the worker thread */
+	struct crypto_hash *integrity_r_tfm; /* to be used by the receiver thread */
+	void *int_dig_out;
+	void *int_dig_in;
+	void *int_dig_vv;
+	wait_queue_head_t seq_wait;
+	atomic_t packet_seq;
+	unsigned int peer_seq;
+	spinlock_t peer_seq_lock;
+	unsigned int minor;
+	unsigned long comm_bm_set; /* communicated number of set bits. */
+	cpumask_var_t cpu_mask;
+	struct bm_io_work bm_io_work;
+	u64 ed_uuid; /* UUID of the exposed data */
+	struct mutex state_mutex;
+	char congestion_reason;  /* Why we where congested... */
+};
+
+static inline struct drbd_conf *minor_to_mdev(unsigned int minor)
+{
+	struct drbd_conf *mdev;
+
+	mdev = minor < minor_count ? minor_table[minor] : NULL;
+
+	return mdev;
+}
+
+static inline unsigned int mdev_to_minor(struct drbd_conf *mdev)
+{
+	return mdev->minor;
+}
+
+/* returns 1 if it was successfull,
+ * returns 0 if there was no data socket.
+ * so wherever you are going to use the data.socket, e.g. do
+ * if (!drbd_get_data_sock(mdev))
+ *	return 0;
+ *	CODE();
+ * drbd_put_data_sock(mdev);
+ */
+static inline int drbd_get_data_sock(struct drbd_conf *mdev)
+{
+	mutex_lock(&mdev->data.mutex);
+	/* drbd_disconnect() could have called drbd_free_sock()
+	 * while we were waiting in down()... */
+	if (unlikely(mdev->data.socket == NULL)) {
+		mutex_unlock(&mdev->data.mutex);
+		return 0;
+	}
+	return 1;
+}
+
+static inline void drbd_put_data_sock(struct drbd_conf *mdev)
+{
+	mutex_unlock(&mdev->data.mutex);
+}
+
+/*
+ * function declarations
+ *************************/
+
+/* drbd_main.c */
+
+enum chg_state_flags {
+	CS_HARD	= 1,
+	CS_VERBOSE = 2,
+	CS_WAIT_COMPLETE = 4,
+	CS_SERIALIZE    = 8,
+	CS_ORDERED      = CS_WAIT_COMPLETE + CS_SERIALIZE,
+};
+
+extern void drbd_init_set_defaults(struct drbd_conf *mdev);
+extern int drbd_change_state(struct drbd_conf *mdev, enum chg_state_flags f,
+			union drbd_state mask, union drbd_state val);
+extern void drbd_force_state(struct drbd_conf *, union drbd_state,
+			union drbd_state);
+extern int _drbd_request_state(struct drbd_conf *, union drbd_state,
+			union drbd_state, enum chg_state_flags);
+extern int __drbd_set_state(struct drbd_conf *, union drbd_state,
+			    enum chg_state_flags, struct completion *done);
+extern void print_st_err(struct drbd_conf *, union drbd_state,
+			union drbd_state, int);
+extern int  drbd_thread_start(struct drbd_thread *thi);
+extern void _drbd_thread_stop(struct drbd_thread *thi, int restart, int wait);
+#ifdef CONFIG_SMP
+extern void drbd_thread_current_set_cpu(struct drbd_conf *mdev);
+extern void drbd_calc_cpu_mask(struct drbd_conf *mdev);
+#else
+#define drbd_thread_current_set_cpu(A) ({})
+#define drbd_calc_cpu_mask(A) ({})
+#endif
+extern void drbd_free_resources(struct drbd_conf *mdev);
+extern void tl_release(struct drbd_conf *mdev, unsigned int barrier_nr,
+		       unsigned int set_size);
+extern void tl_clear(struct drbd_conf *mdev);
+extern void _tl_add_barrier(struct drbd_conf *, struct drbd_tl_epoch *);
+extern void drbd_free_sock(struct drbd_conf *mdev);
+extern int drbd_send(struct drbd_conf *mdev, struct socket *sock,
+			void *buf, size_t size, unsigned msg_flags);
+extern int drbd_send_protocol(struct drbd_conf *mdev);
+extern int drbd_send_uuids(struct drbd_conf *mdev);
+extern int drbd_send_uuids_skip_initial_sync(struct drbd_conf *mdev);
+extern int drbd_send_sync_uuid(struct drbd_conf *mdev, u64 val);
+extern int drbd_send_sizes(struct drbd_conf *mdev, int trigger_reply);
+extern int _drbd_send_state(struct drbd_conf *mdev);
+extern int drbd_send_state(struct drbd_conf *mdev);
+extern int _drbd_send_cmd(struct drbd_conf *mdev, struct socket *sock,
+			enum drbd_packets cmd, struct p_header *h,
+			size_t size, unsigned msg_flags);
+#define USE_DATA_SOCKET 1
+#define USE_META_SOCKET 0
+extern int drbd_send_cmd(struct drbd_conf *mdev, int use_data_socket,
+			enum drbd_packets cmd, struct p_header *h,
+			size_t size);
+extern int drbd_send_cmd2(struct drbd_conf *mdev, enum drbd_packets cmd,
+			char *data, size_t size);
+extern int drbd_send_sync_param(struct drbd_conf *mdev, struct syncer_conf *sc);
+extern int drbd_send_b_ack(struct drbd_conf *mdev, u32 barrier_nr,
+			u32 set_size);
+extern int drbd_send_ack(struct drbd_conf *mdev, enum drbd_packets cmd,
+			struct drbd_epoch_entry *e);
+extern int drbd_send_ack_rp(struct drbd_conf *mdev, enum drbd_packets cmd,
+			struct p_block_req *rp);
+extern int drbd_send_ack_dp(struct drbd_conf *mdev, enum drbd_packets cmd,
+			struct p_data *dp);
+extern int drbd_send_ack_ex(struct drbd_conf *mdev, enum drbd_packets cmd,
+			    sector_t sector, int blksize, u64 block_id);
+extern int drbd_send_block(struct drbd_conf *mdev, enum drbd_packets cmd,
+			   struct drbd_epoch_entry *e);
+extern int drbd_send_dblock(struct drbd_conf *mdev, struct drbd_request *req);
+extern int _drbd_send_barrier(struct drbd_conf *mdev,
+			struct drbd_tl_epoch *barrier);
+extern int drbd_send_drequest(struct drbd_conf *mdev, int cmd,
+			      sector_t sector, int size, u64 block_id);
+extern int drbd_send_drequest_csum(struct drbd_conf *mdev,
+				   sector_t sector,int size,
+				   void *digest, int digest_size,
+				   enum drbd_packets cmd);
+extern int drbd_send_ov_request(struct drbd_conf *mdev,sector_t sector,int size);
+
+extern int drbd_send_bitmap(struct drbd_conf *mdev);
+extern int _drbd_send_bitmap(struct drbd_conf *mdev);
+extern int drbd_send_sr_reply(struct drbd_conf *mdev, int retcode);
+extern void drbd_free_bc(struct drbd_backing_dev *ldev);
+extern void drbd_mdev_cleanup(struct drbd_conf *mdev);
+
+/* drbd_meta-data.c (still in drbd_main.c) */
+extern void drbd_md_sync(struct drbd_conf *mdev);
+extern int  drbd_md_read(struct drbd_conf *mdev, struct drbd_backing_dev *bdev);
+/* maybe define them below as inline? */
+extern void drbd_uuid_set(struct drbd_conf *mdev, int idx, u64 val) __must_hold(local);
+extern void _drbd_uuid_set(struct drbd_conf *mdev, int idx, u64 val) __must_hold(local);
+extern void drbd_uuid_new_current(struct drbd_conf *mdev) __must_hold(local);
+extern void _drbd_uuid_new_current(struct drbd_conf *mdev) __must_hold(local);
+extern void drbd_uuid_set_bm(struct drbd_conf *mdev, u64 val) __must_hold(local);
+extern void drbd_md_set_flag(struct drbd_conf *mdev, int flags) __must_hold(local);
+extern void drbd_md_clear_flag(struct drbd_conf *mdev, int flags)__must_hold(local);
+extern int drbd_md_test_flag(struct drbd_backing_dev *, int);
+extern void drbd_md_mark_dirty(struct drbd_conf *mdev);
+extern void drbd_queue_bitmap_io(struct drbd_conf *mdev,
+				 int (*io_fn)(struct drbd_conf *),
+				 void (*done)(struct drbd_conf *, int),
+				 char *why);
+extern int drbd_bmio_set_n_write(struct drbd_conf *mdev);
+extern int drbd_bmio_clear_n_write(struct drbd_conf *mdev);
+extern int drbd_bitmap_io(struct drbd_conf *mdev, int (*io_fn)(struct drbd_conf *), char *why);
+
+
+/* Meta data layout
+   We reserve a 128MB Block (4k aligned)
+   * either at the end of the backing device
+   * or on a seperate meta data device. */
+
+#define MD_RESERVED_SECT (128LU << 11)  /* 128 MB, unit sectors */
+/* The following numbers are sectors */
+#define MD_AL_OFFSET 8	    /* 8 Sectors after start of meta area */
+#define MD_AL_MAX_SIZE 64   /* = 32 kb LOG  ~ 3776 extents ~ 14 GB Storage */
+/* Allows up to about 3.8TB */
+#define MD_BM_OFFSET (MD_AL_OFFSET + MD_AL_MAX_SIZE)
+
+/* Since the smalles IO unit is usually 512 byte */
+#define MD_SECTOR_SHIFT	 9
+#define MD_SECTOR_SIZE	 (1<<MD_SECTOR_SHIFT)
+
+/* activity log */
+#define AL_EXTENTS_PT ((MD_SECTOR_SIZE-12)/8-1) /* 61 ; Extents per 512B sector */
+#define AL_EXTENT_SHIFT 22		 /* One extent represents 4M Storage */
+#define AL_EXTENT_SIZE (1<<AL_EXTENT_SHIFT)
+
+#if BITS_PER_LONG == 32
+#define LN2_BPL 5
+#define cpu_to_lel(A) cpu_to_le32(A)
+#define lel_to_cpu(A) le32_to_cpu(A)
+#elif BITS_PER_LONG == 64
+#define LN2_BPL 6
+#define cpu_to_lel(A) cpu_to_le64(A)
+#define lel_to_cpu(A) le64_to_cpu(A)
+#else
+#error "LN2 of BITS_PER_LONG unknown!"
+#endif
+
+/* resync bitmap */
+/* 16MB sized 'bitmap extent' to track syncer usage */
+struct bm_extent {
+	int rs_left; /* number of bits set (out of sync) in this extent. */
+	int rs_failed; /* number of failed resync requests in this extent. */
+	unsigned long flags;
+	struct lc_element lce;
+};
+
+#define BME_NO_WRITES  0  /* bm_extent.flags: no more requests on this one! */
+#define BME_LOCKED     1  /* bm_extent.flags: syncer active on this one. */
+
+/* drbd_bitmap.c */
+/*
+ * We need to store one bit for a block.
+ * Example: 1GB disk @ 4096 byte blocks ==> we need 32 KB bitmap.
+ * Bit 0 ==> local node thinks this block is binary identical on both nodes
+ * Bit 1 ==> local node thinks this block needs to be synced.
+ */
+
+#define BM_BLOCK_SHIFT  12			 /* 4k per bit */
+#define BM_BLOCK_SIZE	 (1<<BM_BLOCK_SHIFT)
+/* (9+3) : 512 bytes @ 8 bits; representing 16M storage
+ * per sector of on disk bitmap */
+#define BM_EXT_SHIFT	 (BM_BLOCK_SHIFT + MD_SECTOR_SHIFT + 3)  /* = 24 */
+#define BM_EXT_SIZE	 (1<<BM_EXT_SHIFT)
+
+#if (BM_EXT_SHIFT != 24) || (BM_BLOCK_SHIFT != 12)
+#error "HAVE YOU FIXED drbdmeta AS WELL??"
+#endif
+
+/* thus many _storage_ sectors are described by one bit */
+#define BM_SECT_TO_BIT(x)   ((x)>>(BM_BLOCK_SHIFT-9))
+#define BM_BIT_TO_SECT(x)   ((sector_t)(x)<<(BM_BLOCK_SHIFT-9))
+#define BM_SECT_PER_BIT     BM_BIT_TO_SECT(1)
+
+/* bit to represented kilo byte conversion */
+#define Bit2KB(bits) ((bits)<<(BM_BLOCK_SHIFT-10))
+
+/* in which _bitmap_ extent (resp. sector) the bit for a certain
+ * _storage_ sector is located in */
+#define BM_SECT_TO_EXT(x)   ((x)>>(BM_EXT_SHIFT-9))
+
+/* how much _storage_ sectors we have per bitmap sector */
+#define BM_EXT_TO_SECT(x)   ((sector_t)(x) << (BM_EXT_SHIFT-9))
+#define BM_SECT_PER_EXT     BM_EXT_TO_SECT(1)
+
+/* in one sector of the bitmap, we have this many activity_log extents. */
+#define AL_EXT_PER_BM_SECT  (1 << (BM_EXT_SHIFT - AL_EXTENT_SHIFT))
+#define BM_WORDS_PER_AL_EXT (1 << (AL_EXTENT_SHIFT-BM_BLOCK_SHIFT-LN2_BPL))
+
+#define BM_BLOCKS_PER_BM_EXT_B (BM_EXT_SHIFT - BM_BLOCK_SHIFT)
+#define BM_BLOCKS_PER_BM_EXT_MASK  ((1<<BM_BLOCKS_PER_BM_EXT_B) - 1)
+
+/* the extent in "PER_EXTENT" below is an activity log extent
+ * we need that many (long words/bytes) to store the bitmap
+ *		     of one AL_EXTENT_SIZE chunk of storage.
+ * we can store the bitmap for that many AL_EXTENTS within
+ * one sector of the _on_disk_ bitmap:
+ * bit	 0	  bit 37   bit 38	     bit (512*8)-1
+ *	     ...|........|........|.. // ..|........|
+ * sect. 0	 `296	  `304			   ^(512*8*8)-1
+ *
+#define BM_WORDS_PER_EXT    ( (AL_EXT_SIZE/BM_BLOCK_SIZE) / BITS_PER_LONG )
+#define BM_BYTES_PER_EXT    ( (AL_EXT_SIZE/BM_BLOCK_SIZE) / 8 )  // 128
+#define BM_EXT_PER_SECT	    ( 512 / BM_BYTES_PER_EXTENT )	 //   4
+ */
+
+#define DRBD_MAX_SECTORS_32 (0xffffffffLU)
+#define DRBD_MAX_SECTORS_BM \
+	  ((MD_RESERVED_SECT - MD_BM_OFFSET) * (1LL<<(BM_EXT_SHIFT-9)))
+#if DRBD_MAX_SECTORS_BM < DRBD_MAX_SECTORS_32
+#define DRBD_MAX_SECTORS      DRBD_MAX_SECTORS_BM
+#define DRBD_MAX_SECTORS_FLEX DRBD_MAX_SECTORS_BM
+#elif !defined(CONFIG_LBD) && BITS_PER_LONG == 32
+#define DRBD_MAX_SECTORS      DRBD_MAX_SECTORS_32
+#define DRBD_MAX_SECTORS_FLEX DRBD_MAX_SECTORS_32
+#else
+#define DRBD_MAX_SECTORS      DRBD_MAX_SECTORS_BM
+/* 16 TB in units of sectors */
+#if BITS_PER_LONG == 32
+/* adjust by one page worth of bitmap,
+ * so we won't wrap around in drbd_bm_find_next_bit.
+ * you should use 64bit OS for that much storage, anyways. */
+#define DRBD_MAX_SECTORS_FLEX BM_BIT_TO_SECT(0xffff7fff)
+#else
+#define DRBD_MAX_SECTORS_FLEX BM_BIT_TO_SECT(0x1LU << 32)
+#endif
+#endif
+
+/* Sector shift value for the "hash" functions of tl_hash and ee_hash tables.
+ * With a value of 6 all IO in one 32K block make it to the same slot of the
+ * hash table. */
+#define HT_SHIFT 6
+#define DRBD_MAX_SEGMENT_SIZE (1U<<(9+HT_SHIFT))
+
+/* Number of elements in the app_reads_hash */
+#define APP_R_HSIZE 15
+
+extern int  drbd_bm_init(struct drbd_conf *mdev);
+extern int  drbd_bm_resize(struct drbd_conf *mdev, sector_t sectors);
+extern void drbd_bm_cleanup(struct drbd_conf *mdev);
+extern void drbd_bm_set_all(struct drbd_conf *mdev);
+extern void drbd_bm_clear_all(struct drbd_conf *mdev);
+extern int  drbd_bm_set_bits(
+		struct drbd_conf *mdev, unsigned long s, unsigned long e);
+extern int  drbd_bm_clear_bits(
+		struct drbd_conf *mdev, unsigned long s, unsigned long e);
+/* bm_set_bits variant for use while holding drbd_bm_lock */
+extern void _drbd_bm_set_bits(struct drbd_conf *mdev,
+		const unsigned long s, const unsigned long e);
+extern int  drbd_bm_test_bit(struct drbd_conf *mdev, unsigned long bitnr);
+extern int  drbd_bm_e_weight(struct drbd_conf *mdev, unsigned long enr);
+extern int  drbd_bm_write_sect(struct drbd_conf *mdev, unsigned long enr) __must_hold(local);
+extern int  drbd_bm_read(struct drbd_conf *mdev) __must_hold(local);
+extern int  drbd_bm_write(struct drbd_conf *mdev) __must_hold(local);
+extern unsigned long drbd_bm_ALe_set_all(struct drbd_conf *mdev,
+		unsigned long al_enr);
+extern size_t	     drbd_bm_words(struct drbd_conf *mdev);
+extern unsigned long drbd_bm_bits(struct drbd_conf *mdev);
+extern sector_t      drbd_bm_capacity(struct drbd_conf *mdev);
+extern unsigned long drbd_bm_find_next(struct drbd_conf *mdev, unsigned long bm_fo);
+/* bm_find_next variants for use while you hold drbd_bm_lock() */
+extern unsigned long _drbd_bm_find_next(struct drbd_conf *mdev, unsigned long bm_fo);
+extern unsigned long _drbd_bm_find_next_zero(struct drbd_conf *mdev, unsigned long bm_fo);
+extern unsigned long drbd_bm_total_weight(struct drbd_conf *mdev);
+extern int drbd_bm_rs_done(struct drbd_conf *mdev);
+/* for receive_bitmap */
+extern void drbd_bm_merge_lel(struct drbd_conf *mdev, size_t offset,
+		size_t number, unsigned long *buffer);
+/* for _drbd_send_bitmap and drbd_bm_write_sect */
+extern void drbd_bm_get_lel(struct drbd_conf *mdev, size_t offset,
+		size_t number, unsigned long *buffer);
+
+extern void drbd_bm_lock(struct drbd_conf *mdev, char *why);
+extern void drbd_bm_unlock(struct drbd_conf *mdev);
+
+extern int drbd_bm_count_bits(struct drbd_conf *mdev, const unsigned long s, const unsigned long e);
+/* drbd_main.c */
+
+extern struct kmem_cache *drbd_request_cache;
+extern struct kmem_cache *drbd_ee_cache;	/* epoch entries */
+extern struct kmem_cache *drbd_bm_ext_cache;	/* bitmap extents */
+extern struct kmem_cache *drbd_al_ext_cache;	/* activity log extents */
+extern mempool_t *drbd_request_mempool;
+extern mempool_t *drbd_ee_mempool;
+
+extern struct page *drbd_pp_pool; /* drbd's page pool */
+extern spinlock_t   drbd_pp_lock;
+extern int	    drbd_pp_vacant;
+extern wait_queue_head_t drbd_pp_wait;
+
+extern rwlock_t global_state_lock;
+
+extern struct drbd_conf *drbd_new_device(unsigned int minor);
+extern void drbd_free_mdev(struct drbd_conf *mdev);
+
+extern int proc_details;
+
+/* drbd_req */
+extern int drbd_make_request_26(struct request_queue *q, struct bio *bio);
+extern int drbd_read_remote(struct drbd_conf *mdev, struct drbd_request *req);
+extern int drbd_merge_bvec(struct request_queue *q, struct bvec_merge_data *bvm, struct bio_vec *bvec);
+extern int is_valid_ar_handle(struct drbd_request *, sector_t);
+
+
+/* drbd_nl.c */
+extern void drbd_suspend_io(struct drbd_conf *mdev);
+extern void drbd_resume_io(struct drbd_conf *mdev);
+extern char *ppsize(char *buf, unsigned long long size);
+extern sector_t drbd_new_dev_size(struct drbd_conf *,
+		struct drbd_backing_dev *);
+enum determine_dev_size { dev_size_error = -1, unchanged = 0, shrunk = 1, grew = 2 };
+extern enum determine_dev_size drbd_determin_dev_size(struct drbd_conf *) __must_hold(local);
+extern void resync_after_online_grow(struct drbd_conf *);
+extern void drbd_setup_queue_param(struct drbd_conf *mdev, unsigned int) __must_hold(local);
+extern int drbd_set_role(struct drbd_conf *mdev, enum drbd_role new_role,
+		int force);
+enum drbd_disk_state drbd_try_outdate_peer(struct drbd_conf *mdev);
+extern int drbd_khelper(struct drbd_conf *mdev, char *cmd);
+
+/* drbd_worker.c */
+extern int drbd_worker(struct drbd_thread *thi);
+extern int drbd_alter_sa(struct drbd_conf *mdev, int na);
+extern void drbd_start_resync(struct drbd_conf *mdev, enum drbd_conns side);
+extern void resume_next_sg(struct drbd_conf *mdev);
+extern void suspend_other_sg(struct drbd_conf *mdev);
+extern int drbd_resync_finished(struct drbd_conf *mdev);
+/* maybe rather drbd_main.c ? */
+extern int drbd_md_sync_page_io(struct drbd_conf *mdev,
+		struct drbd_backing_dev *bdev, sector_t sector, int rw);
+extern void drbd_ov_oos_found(struct drbd_conf*, sector_t, int);
+
+static inline void ov_oos_print(struct drbd_conf *mdev)
+{
+	if (mdev->ov_last_oos_size) {
+		dev_err(DEV, "Out of sync: start=%llu, size=%lu (sectors)\n",
+		     (unsigned long long)mdev->ov_last_oos_start,
+		     (unsigned long)mdev->ov_last_oos_size);
+	}
+	mdev->ov_last_oos_size=0;
+}
+
+
+extern void drbd_csum(struct drbd_conf *, struct crypto_hash *, struct bio *, void *);
+/* worker callbacks */
+extern int w_req_cancel_conflict(struct drbd_conf *, struct drbd_work *, int);
+extern int w_read_retry_remote(struct drbd_conf *, struct drbd_work *, int);
+extern int w_e_end_data_req(struct drbd_conf *, struct drbd_work *, int);
+extern int w_e_end_rsdata_req(struct drbd_conf *, struct drbd_work *, int);
+extern int w_e_end_csum_rs_req(struct drbd_conf *, struct drbd_work *, int);
+extern int w_e_end_ov_reply(struct drbd_conf *, struct drbd_work *, int);
+extern int w_e_end_ov_req(struct drbd_conf *, struct drbd_work *, int);
+extern int w_ov_finished(struct drbd_conf *, struct drbd_work *, int);
+extern int w_resync_inactive(struct drbd_conf *, struct drbd_work *, int);
+extern int w_resume_next_sg(struct drbd_conf *, struct drbd_work *, int);
+extern int w_io_error(struct drbd_conf *, struct drbd_work *, int);
+extern int w_send_write_hint(struct drbd_conf *, struct drbd_work *, int);
+extern int w_make_resync_request(struct drbd_conf *, struct drbd_work *, int);
+extern int w_send_dblock(struct drbd_conf *, struct drbd_work *, int);
+extern int w_send_barrier(struct drbd_conf *, struct drbd_work *, int);
+extern int w_send_read_req(struct drbd_conf *, struct drbd_work *, int);
+extern int w_prev_work_done(struct drbd_conf *, struct drbd_work *, int);
+extern int w_e_reissue(struct drbd_conf *, struct drbd_work *, int);
+
+extern void resync_timer_fn(unsigned long data);
+
+/* drbd_receiver.c */
+extern int drbd_release_ee(struct drbd_conf *mdev, struct list_head *list);
+extern struct drbd_epoch_entry *drbd_alloc_ee(struct drbd_conf *mdev,
+					    u64 id,
+					    sector_t sector,
+					    unsigned int data_size,
+					    gfp_t gfp_mask) __must_hold(local);
+extern void drbd_free_ee(struct drbd_conf *mdev, struct drbd_epoch_entry *e);
+extern void drbd_wait_ee_list_empty(struct drbd_conf *mdev,
+		struct list_head *head);
+extern void _drbd_wait_ee_list_empty(struct drbd_conf *mdev,
+		struct list_head *head);
+extern void drbd_set_recv_tcq(struct drbd_conf *mdev, int tcq_enabled);
+extern void _drbd_clear_done_ee(struct drbd_conf *mdev, struct list_head *to_be_freed);
+extern void drbd_flush_workqueue(struct drbd_conf *mdev);
+
+/* yes, there is kernel_setsockopt, but only since 2.6.18. we don't need to
+ * mess with get_fs/set_fs, we know we are KERNEL_DS always. */
+static inline int drbd_setsockopt(struct socket *sock, int level, int optname,
+			char __user *optval, int optlen)
+{
+	int err;
+	if (level == SOL_SOCKET)
+		err = sock_setsockopt(sock, level, optname, optval, optlen);
+	else
+		err = sock->ops->setsockopt(sock, level, optname, optval,
+					    optlen);
+	return err;
+}
+
+static inline void drbd_tcp_cork(struct socket *sock)
+{
+	int __user val = 1;
+	(void) drbd_setsockopt(sock, SOL_TCP, TCP_CORK,
+			(char __user *)&val, sizeof(val));
+}
+
+static inline void drbd_tcp_uncork(struct socket *sock)
+{
+	int __user val = 0;
+	(void) drbd_setsockopt(sock, SOL_TCP, TCP_CORK,
+			(char __user *)&val, sizeof(val));
+}
+
+static inline void drbd_tcp_nodelay(struct socket *sock)
+{
+	int __user val = 1;
+	(void) drbd_setsockopt(sock, SOL_TCP, TCP_NODELAY,
+			(char __user *)&val, sizeof(val));
+}
+
+static inline void drbd_tcp_quickack(struct socket *sock)
+{
+	int __user val = 1;
+	(void) drbd_setsockopt(sock, SOL_TCP, TCP_QUICKACK,
+			(char __user *)&val, sizeof(val));
+}
+
+void drbd_bump_write_ordering(struct drbd_conf *mdev, enum write_ordering_e wo);
+
+/* drbd_proc.c */
+extern struct proc_dir_entry *drbd_proc;
+extern struct file_operations drbd_proc_fops;
+extern const char *drbd_conn_str(enum drbd_conns s);
+extern const char *drbd_role_str(enum drbd_role s);
+
+/* drbd_actlog.c */
+extern void drbd_al_begin_io(struct drbd_conf *mdev, sector_t sector);
+extern void drbd_al_complete_io(struct drbd_conf *mdev, sector_t sector);
+extern void drbd_rs_complete_io(struct drbd_conf *mdev, sector_t sector);
+extern int drbd_rs_begin_io(struct drbd_conf *mdev, sector_t sector);
+extern int drbd_try_rs_begin_io(struct drbd_conf *mdev, sector_t sector);
+extern void drbd_rs_cancel_all(struct drbd_conf *mdev);
+extern int drbd_rs_del_all(struct drbd_conf *mdev);
+extern void drbd_rs_failed_io(struct drbd_conf *mdev,
+		sector_t sector, int size);
+extern int drbd_al_read_log(struct drbd_conf *mdev, struct drbd_backing_dev *);
+extern void __drbd_set_in_sync(struct drbd_conf *mdev, sector_t sector,
+		int size, const char *file, const unsigned int line);
+#define drbd_set_in_sync(mdev, sector, size) \
+	__drbd_set_in_sync(mdev, sector, size, __FILE__, __LINE__)
+extern void __drbd_set_out_of_sync(struct drbd_conf *mdev, sector_t sector,
+		int size, const char *file, const unsigned int line);
+#define drbd_set_out_of_sync(mdev, sector, size) \
+	__drbd_set_out_of_sync(mdev, sector, size, __FILE__, __LINE__)
+extern void drbd_al_apply_to_bm(struct drbd_conf *mdev);
+extern void drbd_al_to_on_disk_bm(struct drbd_conf *mdev);
+extern void drbd_al_shrink(struct drbd_conf *mdev);
+
+
+/* drbd_nl.c */
+
+void drbd_nl_cleanup(void);
+int __init drbd_nl_init(void);
+void drbd_bcast_state(struct drbd_conf *mdev, union drbd_state);
+void drbd_bcast_sync_progress(struct drbd_conf *mdev);
+void drbd_bcast_ee(struct drbd_conf *mdev,
+		const char *reason, const int dgs,
+		const char* seen_hash, const char* calc_hash,
+		const struct drbd_epoch_entry* e);
+
+
+/**
+ * DOC: DRBD State macros
+ *
+ * These macros are used to express state changes in easily readable form.
+ *
+ * The NS macros expand to a mask and a value, that can be bit ored onto the
+ * current state as soon as the spinlock (req_lock) was taken.
+ *
+ * The _NS macros are used for state functions that get called with the
+ * spinlock. These macros expand directly to the new state value.
+ *
+ * Besides the basic forms NS() and _NS() additional _?NS[23] are defined
+ * to express state changes that affect more than one aspect of the state.
+ *
+ * E.g. NS2(conn, C_CONNECTED, peer, R_SECONDARY)
+ * Means that the network connection was established and that the peer
+ * is in secondary role.
+ */
+#define role_MASK R_MASK
+#define peer_MASK R_MASK
+#define disk_MASK D_MASK
+#define pdsk_MASK D_MASK
+#define conn_MASK C_MASK
+#define susp_MASK 1
+#define user_isp_MASK 1
+#define aftr_isp_MASK 1
+
+#define NS(T, S) \
+	({ union drbd_state mask; mask.i = 0; mask.T = T##_MASK; mask; }), \
+	({ union drbd_state val; val.i = 0; val.T = (S); val; })
+#define NS2(T1, S1, T2, S2) \
+	({ union drbd_state mask; mask.i = 0; mask.T1 = T1##_MASK; \
+	  mask.T2 = T2##_MASK; mask; }), \
+	({ union drbd_state val; val.i = 0; val.T1 = (S1); \
+	  val.T2 = (S2); val; })
+#define NS3(T1, S1, T2, S2, T3, S3) \
+	({ union drbd_state mask; mask.i = 0; mask.T1 = T1##_MASK; \
+	  mask.T2 = T2##_MASK; mask.T3 = T3##_MASK; mask; }), \
+	({ union drbd_state val;  val.i = 0; val.T1 = (S1); \
+	  val.T2 = (S2); val.T3 = (S3); val; })
+
+#define _NS(D, T, S) \
+	D, ({ union drbd_state __ns; __ns.i = D->state.i; __ns.T = (S); __ns; })
+#define _NS2(D, T1, S1, T2, S2) \
+	D, ({ union drbd_state __ns; __ns.i = D->state.i; __ns.T1 = (S1); \
+	__ns.T2 = (S2); __ns; })
+#define _NS3(D, T1, S1, T2, S2, T3, S3) \
+	D, ({ union drbd_state __ns; __ns.i = D->state.i; __ns.T1 = (S1); \
+	__ns.T2 = (S2); __ns.T3 = (S3); __ns; })
+
+/*
+ * inline helper functions
+ *************************/
+
+static inline void drbd_state_lock(struct drbd_conf *mdev)
+{
+	wait_event(mdev->misc_wait,
+		   !test_and_set_bit(CLUSTER_ST_CHANGE, &mdev->flags));
+}
+
+static inline void drbd_state_unlock(struct drbd_conf *mdev)
+{
+	clear_bit(CLUSTER_ST_CHANGE, &mdev->flags);
+	wake_up(&mdev->misc_wait);
+}
+
+static inline int _drbd_set_state(struct drbd_conf *mdev,
+				   union drbd_state ns, enum chg_state_flags flags,
+				   struct completion *done)
+{
+	int rv;
+
+	read_lock(&global_state_lock);
+	rv = __drbd_set_state(mdev, ns, flags, done);
+	read_unlock(&global_state_lock);
+
+	return rv;
+}
+
+/**
+ * drbd_request_state() - Reqest a state change
+ * @mdev:	DRBD device.
+ * @mask:	mask of state bits to change.
+ * @val:	value of new state bits.
+ *
+ * This is the most graceful way of requesting a state change. It is verbose
+ * quite verbose in case the state change is not possible, and all those
+ * state changes are globally serialized.
+ */
+static inline int drbd_request_state(struct drbd_conf *mdev,
+				     union drbd_state mask,
+				     union drbd_state val)
+{
+	return _drbd_request_state(mdev, mask, val, CS_VERBOSE + CS_ORDERED);
+}
+
+#define __drbd_chk_io_error(m,f) __drbd_chk_io_error_(m,f, __func__)
+static inline void __drbd_chk_io_error_(struct drbd_conf *mdev, int forcedetach, const char *where)
+{
+	switch (mdev->ldev->dc.on_io_error) {
+	case EP_PASS_ON:
+		if (!forcedetach) {
+			if (printk_ratelimit())
+				dev_err(DEV, "Local IO failed in %s."
+					     "Passing error on...\n", where);
+			break;
+		}
+		/* NOTE fall through to detach case if forcedetach set */
+	case EP_DETACH:
+	case EP_CALL_HELPER:
+		if (mdev->state.disk > D_FAILED) {
+			_drbd_set_state(_NS(mdev, disk, D_FAILED), CS_HARD, NULL);
+			dev_err(DEV, "Local IO failed in %s."
+				     "Detaching...\n", where);
+		}
+		break;
+	}
+}
+
+/**
+ * drbd_chk_io_error: Handle the on_io_error setting, should be called from all io completion handlers
+ * @mdev:	 DRBD device.
+ * @error:	 Error code passed to the IO completion callback
+ * @forcedetach: Force detach. I.e. the error happened while accessing the meta data
+ *
+ * See also drbd_main.c:after_state_ch() if (os.disk > D_FAILED && ns.disk == D_FAILED)
+ */
+#define drbd_chk_io_error(m,e,f) drbd_chk_io_error_(m,e,f, __func__)
+static inline void drbd_chk_io_error_(struct drbd_conf *mdev,
+	int error, int forcedetach, const char *where)
+{
+	if (error) {
+		unsigned long flags;
+		spin_lock_irqsave(&mdev->req_lock, flags);
+		__drbd_chk_io_error_(mdev, forcedetach, where);
+		spin_unlock_irqrestore(&mdev->req_lock, flags);
+	}
+}
+
+
+/**
+ * drbd_md_first_sector() - Returns the first sector number of the meta data area
+ * @bdev:	Meta data block device.
+ *
+ * BTW, for internal meta data, this happens to be the maximum capacity
+ * we could agree upon with our peer node.
+ */
+static inline sector_t drbd_md_first_sector(struct drbd_backing_dev *bdev)
+{
+	switch (bdev->dc.meta_dev_idx) {
+	case DRBD_MD_INDEX_INTERNAL:
+	case DRBD_MD_INDEX_FLEX_INT:
+		return bdev->md.md_offset + bdev->md.bm_offset;
+	case DRBD_MD_INDEX_FLEX_EXT:
+	default:
+		return bdev->md.md_offset;
+	}
+}
+
+/**
+ * drbd_md_last_sector() - Return the last sector number of the meta data area
+ * @bdev:	Meta data block device.
+ */
+static inline sector_t drbd_md_last_sector(struct drbd_backing_dev *bdev)
+{
+	switch (bdev->dc.meta_dev_idx) {
+	case DRBD_MD_INDEX_INTERNAL:
+	case DRBD_MD_INDEX_FLEX_INT:
+		return bdev->md.md_offset + MD_AL_OFFSET - 1;
+	case DRBD_MD_INDEX_FLEX_EXT:
+	default:
+		return bdev->md.md_offset + bdev->md.md_size_sect;
+	}
+}
+
+/* Returns the number of 512 byte sectors of the device */
+static inline sector_t drbd_get_capacity(struct block_device *bdev)
+{
+	/* return bdev ? get_capacity(bdev->bd_disk) : 0; */
+	return bdev ? bdev->bd_inode->i_size >> 9 : 0;
+}
+
+/**
+ * drbd_get_max_capacity() - Returns the capacity we announce to out peer
+ * @bdev:	Meta data block device.
+ *
+ * returns the capacity we announce to out peer.  we clip ourselves at the
+ * various MAX_SECTORS, because if we don't, current implementation will
+ * oops sooner or later
+ */
+static inline sector_t drbd_get_max_capacity(struct drbd_backing_dev *bdev)
+{
+	sector_t s;
+	switch (bdev->dc.meta_dev_idx) {
+	case DRBD_MD_INDEX_INTERNAL:
+	case DRBD_MD_INDEX_FLEX_INT:
+		s = drbd_get_capacity(bdev->backing_bdev)
+			? min_t(sector_t, DRBD_MAX_SECTORS_FLEX,
+					drbd_md_first_sector(bdev))
+			: 0;
+		break;
+	case DRBD_MD_INDEX_FLEX_EXT:
+		s = min_t(sector_t, DRBD_MAX_SECTORS_FLEX,
+				drbd_get_capacity(bdev->backing_bdev));
+		/* clip at maximum size the meta device can support */
+		s = min_t(sector_t, s,
+			BM_EXT_TO_SECT(bdev->md.md_size_sect
+				     - bdev->md.bm_offset));
+		break;
+	default:
+		s = min_t(sector_t, DRBD_MAX_SECTORS,
+				drbd_get_capacity(bdev->backing_bdev));
+	}
+	return s;
+}
+
+/**
+ * drbd_md_ss__() - Return the sector number of our meta data super block
+ * @mdev:	DRBD device.
+ * @bdev:	Meta data block device.
+ */
+static inline sector_t drbd_md_ss__(struct drbd_conf *mdev,
+				    struct drbd_backing_dev *bdev)
+{
+	switch (bdev->dc.meta_dev_idx) {
+	default: /* external, some index */
+		return MD_RESERVED_SECT * bdev->dc.meta_dev_idx;
+	case DRBD_MD_INDEX_INTERNAL:
+		/* with drbd08, internal meta data is always "flexible" */
+	case DRBD_MD_INDEX_FLEX_INT:
+		/* sizeof(struct md_on_disk_07) == 4k
+		 * position: last 4k aligned block of 4k size */
+		if (!bdev->backing_bdev) {
+			if (__ratelimit(&drbd_ratelimit_state)) {
+				dev_err(DEV, "bdev->backing_bdev==NULL\n");
+				dump_stack();
+			}
+			return 0;
+		}
+		return (drbd_get_capacity(bdev->backing_bdev) & ~7ULL)
+			- MD_AL_OFFSET;
+	case DRBD_MD_INDEX_FLEX_EXT:
+		return 0;
+	}
+}
+
+static inline void
+_drbd_queue_work(struct drbd_work_queue *q, struct drbd_work *w)
+{
+	list_add_tail(&w->list, &q->q);
+	up(&q->s);
+}
+
+static inline void
+drbd_queue_work_front(struct drbd_work_queue *q, struct drbd_work *w)
+{
+	unsigned long flags;
+	spin_lock_irqsave(&q->q_lock, flags);
+	list_add(&w->list, &q->q);
+	up(&q->s); /* within the spinlock,
+		      see comment near end of drbd_worker() */
+	spin_unlock_irqrestore(&q->q_lock, flags);
+}
+
+static inline void
+drbd_queue_work(struct drbd_work_queue *q, struct drbd_work *w)
+{
+	unsigned long flags;
+	spin_lock_irqsave(&q->q_lock, flags);
+	list_add_tail(&w->list, &q->q);
+	up(&q->s); /* within the spinlock,
+		      see comment near end of drbd_worker() */
+	spin_unlock_irqrestore(&q->q_lock, flags);
+}
+
+static inline void wake_asender(struct drbd_conf *mdev)
+{
+	if (test_bit(SIGNAL_ASENDER, &mdev->flags))
+		force_sig(DRBD_SIG, mdev->asender.task);
+}
+
+static inline void request_ping(struct drbd_conf *mdev)
+{
+	set_bit(SEND_PING, &mdev->flags);
+	wake_asender(mdev);
+}
+
+static inline int drbd_send_short_cmd(struct drbd_conf *mdev,
+	enum drbd_packets cmd)
+{
+	struct p_header h;
+	return drbd_send_cmd(mdev, USE_DATA_SOCKET, cmd, &h, sizeof(h));
+}
+
+static inline int drbd_send_ping(struct drbd_conf *mdev)
+{
+	struct p_header h;
+	return drbd_send_cmd(mdev, USE_META_SOCKET, P_PING, &h, sizeof(h));
+}
+
+static inline int drbd_send_ping_ack(struct drbd_conf *mdev)
+{
+	struct p_header h;
+	return drbd_send_cmd(mdev, USE_META_SOCKET, P_PING_ACK, &h, sizeof(h));
+}
+
+static inline void drbd_thread_stop(struct drbd_thread *thi)
+{
+	_drbd_thread_stop(thi, FALSE, TRUE);
+}
+
+static inline void drbd_thread_stop_nowait(struct drbd_thread *thi)
+{
+	_drbd_thread_stop(thi, FALSE, FALSE);
+}
+
+static inline void drbd_thread_restart_nowait(struct drbd_thread *thi)
+{
+	_drbd_thread_stop(thi, TRUE, FALSE);
+}
+
+/* counts how many answer packets packets we expect from our peer,
+ * for either explicit application requests,
+ * or implicit barrier packets as necessary.
+ * increased:
+ *  w_send_barrier
+ *  _req_mod(req, queue_for_net_write or queue_for_net_read);
+ *    it is much easier and equally valid to count what we queue for the
+ *    worker, even before it actually was queued or send.
+ *    (drbd_make_request_common; recovery path on read io-error)
+ * decreased:
+ *  got_BarrierAck (respective tl_clear, tl_clear_barrier)
+ *  _req_mod(req, data_received)
+ *     [from receive_DataReply]
+ *  _req_mod(req, write_acked_by_peer or recv_acked_by_peer or neg_acked)
+ *     [from got_BlockAck (P_WRITE_ACK, P_RECV_ACK)]
+ *     for some reason it is NOT decreased in got_NegAck,
+ *     but in the resulting cleanup code from report_params.
+ *     we should try to remember the reason for that...
+ *  _req_mod(req, send_failed or send_canceled)
+ *  _req_mod(req, connection_lost_while_pending)
+ *     [from tl_clear_barrier]
+ */
+static inline void inc_ap_pending(struct drbd_conf *mdev)
+{
+	atomic_inc(&mdev->ap_pending_cnt);
+}
+
+#define ERR_IF_CNT_IS_NEGATIVE(which)				\
+	if (atomic_read(&mdev->which) < 0)			\
+		dev_err(DEV, "in %s:%d: " #which " = %d < 0 !\n",	\
+		    __func__ , __LINE__ ,			\
+		    atomic_read(&mdev->which))
+
+#define dec_ap_pending(mdev)	do {				\
+	typecheck(struct drbd_conf *, mdev);			\
+	if (atomic_dec_and_test(&mdev->ap_pending_cnt))		\
+		wake_up(&mdev->misc_wait);			\
+	ERR_IF_CNT_IS_NEGATIVE(ap_pending_cnt); } while (0)
+
+/* counts how many resync-related answers we still expect from the peer
+ *		     increase			decrease
+ * C_SYNC_TARGET sends P_RS_DATA_REQUEST (and expects P_RS_DATA_REPLY)
+ * C_SYNC_SOURCE sends P_RS_DATA_REPLY   (and expects P_WRITE_ACK whith ID_SYNCER)
+ *					   (or P_NEG_ACK with ID_SYNCER)
+ */
+static inline void inc_rs_pending(struct drbd_conf *mdev)
+{
+	atomic_inc(&mdev->rs_pending_cnt);
+}
+
+#define dec_rs_pending(mdev)	do {				\
+	typecheck(struct drbd_conf *, mdev);			\
+	atomic_dec(&mdev->rs_pending_cnt);			\
+	ERR_IF_CNT_IS_NEGATIVE(rs_pending_cnt); } while (0)
+
+/* counts how many answers we still need to send to the peer.
+ * increased on
+ *  receive_Data	unless protocol A;
+ *			we need to send a P_RECV_ACK (proto B)
+ *			or P_WRITE_ACK (proto C)
+ *  receive_RSDataReply (recv_resync_read) we need to send a P_WRITE_ACK
+ *  receive_DataRequest (receive_RSDataRequest) we need to send back P_DATA
+ *  receive_Barrier_*	we need to send a P_BARRIER_ACK
+ */
+static inline void inc_unacked(struct drbd_conf *mdev)
+{
+	atomic_inc(&mdev->unacked_cnt);
+}
+
+#define dec_unacked(mdev)	do {				\
+	typecheck(struct drbd_conf *, mdev);			\
+	atomic_dec(&mdev->unacked_cnt);				\
+	ERR_IF_CNT_IS_NEGATIVE(unacked_cnt); } while (0)
+
+#define sub_unacked(mdev, n)	do {				\
+	typecheck(struct drbd_conf *, mdev);			\
+	atomic_sub(n, &mdev->unacked_cnt);			\
+	ERR_IF_CNT_IS_NEGATIVE(unacked_cnt); } while (0)
+
+
+static inline void put_net_conf(struct drbd_conf *mdev)
+{
+	if (atomic_dec_and_test(&mdev->net_cnt))
+		wake_up(&mdev->misc_wait);
+}
+
+/**
+ * get_net_conf() - Increase ref count on mdev->net_conf; Returns 0 if nothing there
+ * @mdev:	DRBD device.
+ *
+ * You have to call put_net_conf() when finished working with mdev->net_conf.
+ */
+static inline int get_net_conf(struct drbd_conf *mdev)
+{
+	int have_net_conf;
+
+	atomic_inc(&mdev->net_cnt);
+	have_net_conf = mdev->state.conn >= C_UNCONNECTED;
+	if (!have_net_conf)
+		put_net_conf(mdev);
+	return have_net_conf;
+}
+
+/**
+ * get_ldev() - Increase the ref count on mdev->ldev. Returns 0 if there is no ldev
+ * @M:		DRBD device.
+ *
+ * You have to call put_ldev() when finished working with mdev->ldev.
+ */
+#define get_ldev(M) __cond_lock(local, _get_ldev_if_state(M,D_INCONSISTENT))
+#define get_ldev_if_state(M,MINS) __cond_lock(local, _get_ldev_if_state(M,MINS))
+
+static inline void put_ldev(struct drbd_conf *mdev)
+{
+	__release(local);
+	if (atomic_dec_and_test(&mdev->local_cnt))
+		wake_up(&mdev->misc_wait);
+	D_ASSERT(atomic_read(&mdev->local_cnt) >= 0);
+}
+
+#ifndef __CHECKER__
+static inline int _get_ldev_if_state(struct drbd_conf *mdev, enum drbd_disk_state mins)
+{
+	int io_allowed;
+
+	atomic_inc(&mdev->local_cnt);
+	io_allowed = (mdev->state.disk >= mins);
+	if (!io_allowed)
+		put_ldev(mdev);
+	return io_allowed;
+}
+#else
+extern int _get_ldev_if_state(struct drbd_conf *mdev, enum drbd_disk_state mins);
+#endif
+
+/* you must have an "get_ldev" reference */
+static inline void drbd_get_syncer_progress(struct drbd_conf *mdev,
+		unsigned long *bits_left, unsigned int *per_mil_done)
+{
+	/*
+	 * this is to break it at compile time when we change that
+	 * (we may feel 4TB maximum storage per drbd is not enough)
+	 */
+	typecheck(unsigned long, mdev->rs_total);
+
+	/* note: both rs_total and rs_left are in bits, i.e. in
+	 * units of BM_BLOCK_SIZE.
+	 * for the percentage, we don't care. */
+
+	*bits_left = drbd_bm_total_weight(mdev) - mdev->rs_failed;
+	/* >> 10 to prevent overflow,
+	 * +1 to prevent division by zero */
+	if (*bits_left > mdev->rs_total) {
+		/* doh. maybe a logic bug somewhere.
+		 * may also be just a race condition
+		 * between this and a disconnect during sync.
+		 * for now, just prevent in-kernel buffer overflow.
+		 */
+		smp_rmb();
+		dev_warn(DEV, "cs:%s rs_left=%lu > rs_total=%lu (rs_failed %lu)\n",
+				drbd_conn_str(mdev->state.conn),
+				*bits_left, mdev->rs_total, mdev->rs_failed);
+		*per_mil_done = 0;
+	} else {
+		/* make sure the calculation happens in long context */
+		unsigned long tmp = 1000UL -
+				(*bits_left >> 10)*1000UL
+				/ ((mdev->rs_total >> 10) + 1UL);
+		*per_mil_done = tmp;
+	}
+}
+
+
+/* this throttles on-the-fly application requests
+ * according to max_buffers settings;
+ * maybe re-implement using semaphores? */
+static inline int drbd_get_max_buffers(struct drbd_conf *mdev)
+{
+	int mxb = 1000000; /* arbitrary limit on open requests */
+	if (get_net_conf(mdev)) {
+		mxb = mdev->net_conf->max_buffers;
+		put_net_conf(mdev);
+	}
+	return mxb;
+}
+
+static inline int drbd_state_is_stable(union drbd_state s)
+{
+
+	/* DO NOT add a default clause, we want the compiler to warn us
+	 * for any newly introduced state we may have forgotten to add here */
+
+	switch ((enum drbd_conns)s.conn) {
+	/* new io only accepted when there is no connection, ... */
+	case C_STANDALONE:
+	case C_WF_CONNECTION:
+	/* ... or there is a well established connection. */
+	case C_CONNECTED:
+	case C_SYNC_SOURCE:
+	case C_SYNC_TARGET:
+	case C_VERIFY_S:
+	case C_VERIFY_T:
+	case C_PAUSED_SYNC_S:
+	case C_PAUSED_SYNC_T:
+		/* maybe stable, look at the disk state */
+		break;
+
+	/* no new io accepted during tansitional states
+	 * like handshake or teardown */
+	case C_DISCONNECTING:
+	case C_UNCONNECTED:
+	case C_TIMEOUT:
+	case C_BROKEN_PIPE:
+	case C_NETWORK_FAILURE:
+	case C_PROTOCOL_ERROR:
+	case C_TEAR_DOWN:
+	case C_WF_REPORT_PARAMS:
+	case C_STARTING_SYNC_S:
+	case C_STARTING_SYNC_T:
+	case C_WF_BITMAP_S:
+	case C_WF_BITMAP_T:
+	case C_WF_SYNC_UUID:
+	case C_MASK:
+		/* not "stable" */
+		return 0;
+	}
+
+	switch ((enum drbd_disk_state)s.disk) {
+	case D_DISKLESS:
+	case D_INCONSISTENT:
+	case D_OUTDATED:
+	case D_CONSISTENT:
+	case D_UP_TO_DATE:
+		/* disk state is stable as well. */
+		break;
+
+	/* no new io accepted during tansitional states */
+	case D_ATTACHING:
+	case D_FAILED:
+	case D_NEGOTIATING:
+	case D_UNKNOWN:
+	case D_MASK:
+		/* not "stable" */
+		return 0;
+	}
+
+	return 1;
+}
+
+static inline int __inc_ap_bio_cond(struct drbd_conf *mdev)
+{
+	int mxb = drbd_get_max_buffers(mdev);
+
+	if (mdev->state.susp)
+		return 0;
+	if (test_bit(SUSPEND_IO, &mdev->flags))
+		return 0;
+
+	/* to avoid potential deadlock or bitmap corruption,
+	 * in various places, we only allow new application io
+	 * to start during "stable" states. */
+
+	/* no new io accepted when attaching or detaching the disk */
+	if (!drbd_state_is_stable(mdev->state))
+		return 0;
+
+	/* since some older kernels don't have atomic_add_unless,
+	 * and we are within the spinlock anyways, we have this workaround.  */
+	if (atomic_read(&mdev->ap_bio_cnt) > mxb)
+		return 0;
+	if (test_bit(BITMAP_IO, &mdev->flags))
+		return 0;
+	return 1;
+}
+
+/* I'd like to use wait_event_lock_irq,
+ * but I'm not sure when it got introduced,
+ * and not sure when it has 3 or 4 arguments */
+static inline void inc_ap_bio(struct drbd_conf *mdev, int one_or_two)
+{
+	/* compare with after_state_ch,
+	 * os.conn != C_WF_BITMAP_S && ns.conn == C_WF_BITMAP_S */
+	DEFINE_WAIT(wait);
+
+	/* we wait here
+	 *    as long as the device is suspended
+	 *    until the bitmap is no longer on the fly during connection
+	 *    handshake as long as we would exeed the max_buffer limit.
+	 *
+	 * to avoid races with the reconnect code,
+	 * we need to atomic_inc within the spinlock. */
+
+	spin_lock_irq(&mdev->req_lock);
+	while (!__inc_ap_bio_cond(mdev)) {
+		prepare_to_wait(&mdev->misc_wait, &wait, TASK_UNINTERRUPTIBLE);
+		spin_unlock_irq(&mdev->req_lock);
+		schedule();
+		finish_wait(&mdev->misc_wait, &wait);
+		spin_lock_irq(&mdev->req_lock);
+	}
+	atomic_add(one_or_two, &mdev->ap_bio_cnt);
+	spin_unlock_irq(&mdev->req_lock);
+}
+
+static inline void dec_ap_bio(struct drbd_conf *mdev)
+{
+	int mxb = drbd_get_max_buffers(mdev);
+	int ap_bio = atomic_dec_return(&mdev->ap_bio_cnt);
+
+	D_ASSERT(ap_bio >= 0);
+	/* this currently does wake_up for every dec_ap_bio!
+	 * maybe rather introduce some type of hysteresis?
+	 * e.g. (ap_bio == mxb/2 || ap_bio == 0) ? */
+	if (ap_bio < mxb)
+		wake_up(&mdev->misc_wait);
+	if (ap_bio == 0 && test_bit(BITMAP_IO, &mdev->flags)) {
+		if (!test_and_set_bit(BITMAP_IO_QUEUED, &mdev->flags))
+			drbd_queue_work(&mdev->data.work, &mdev->bm_io_work.w);
+	}
+}
+
+static inline void drbd_set_ed_uuid(struct drbd_conf *mdev, u64 val)
+{
+	mdev->ed_uuid = val;
+}
+
+static inline int seq_cmp(u32 a, u32 b)
+{
+	/* we assume wrap around at 32bit.
+	 * for wrap around at 24bit (old atomic_t),
+	 * we'd have to
+	 *  a <<= 8; b <<= 8;
+	 */
+	return (s32)(a) - (s32)(b);
+}
+#define seq_lt(a, b) (seq_cmp((a), (b)) < 0)
+#define seq_gt(a, b) (seq_cmp((a), (b)) > 0)
+#define seq_ge(a, b) (seq_cmp((a), (b)) >= 0)
+#define seq_le(a, b) (seq_cmp((a), (b)) <= 0)
+/* CAUTION: please no side effects in arguments! */
+#define seq_max(a, b) ((u32)(seq_gt((a), (b)) ? (a) : (b)))
+
+static inline void update_peer_seq(struct drbd_conf *mdev, unsigned int new_seq)
+{
+	unsigned int m;
+	spin_lock(&mdev->peer_seq_lock);
+	m = seq_max(mdev->peer_seq, new_seq);
+	mdev->peer_seq = m;
+	spin_unlock(&mdev->peer_seq_lock);
+	if (m == new_seq)
+		wake_up(&mdev->seq_wait);
+}
+
+static inline void drbd_update_congested(struct drbd_conf *mdev)
+{
+	struct sock *sk = mdev->data.socket->sk;
+	if (sk->sk_wmem_queued > sk->sk_sndbuf * 4 / 5)
+		set_bit(NET_CONGESTED, &mdev->flags);
+}
+
+static inline int drbd_queue_order_type(struct drbd_conf *mdev)
+{
+	/* sorry, we currently have no working implementation
+	 * of distributed TCQ stuff */
+#ifndef QUEUE_ORDERED_NONE
+#define QUEUE_ORDERED_NONE 0
+#endif
+	return QUEUE_ORDERED_NONE;
+}
+
+static inline void drbd_blk_run_queue(struct request_queue *q)
+{
+	if (q && q->unplug_fn)
+		q->unplug_fn(q);
+}
+
+static inline void drbd_kick_lo(struct drbd_conf *mdev)
+{
+	if (get_ldev(mdev)) {
+		drbd_blk_run_queue(bdev_get_queue(mdev->ldev->backing_bdev));
+		put_ldev(mdev);
+	}
+}
+
+static inline void drbd_md_flush(struct drbd_conf *mdev)
+{
+	int r;
+
+	if (test_bit(MD_NO_BARRIER, &mdev->flags))
+		return;
+
+	r = blkdev_issue_flush(mdev->ldev->md_bdev, NULL);
+	if (r) {
+		set_bit(MD_NO_BARRIER, &mdev->flags);
+		dev_err(DEV, "meta data flush failed with status %d, disabling md-flushes\n", r);
+	}
+}
+
+#endif
diff --git a/drivers/block/drbd/drbd_main.c b/drivers/block/drbd/drbd_main.c
new file mode 100644
index 00000000000..edf0b8031e6
--- /dev/null
+++ b/drivers/block/drbd/drbd_main.c
@@ -0,0 +1,3735 @@
+/*
+   drbd.c
+
+   This file is part of DRBD by Philipp Reisner and Lars Ellenberg.
+
+   Copyright (C) 2001-2008, LINBIT Information Technologies GmbH.
+   Copyright (C) 1999-2008, Philipp Reisner <philipp.reisner@linbit.com>.
+   Copyright (C) 2002-2008, Lars Ellenberg <lars.ellenberg@linbit.com>.
+
+   Thanks to Carter Burden, Bart Grantham and Gennadiy Nerubayev
+   from Logicworks, Inc. for making SDP replication support possible.
+
+   drbd is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 2, or (at your option)
+   any later version.
+
+   drbd is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with drbd; see the file COPYING.  If not, write to
+   the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
+
+ */
+
+#include <linux/autoconf.h>
+#include <linux/module.h>
+#include <linux/version.h>
+#include <linux/drbd.h>
+#include <asm/uaccess.h>
+#include <asm/types.h>
+#include <net/sock.h>
+#include <linux/ctype.h>
+#include <linux/smp_lock.h>
+#include <linux/fs.h>
+#include <linux/file.h>
+#include <linux/proc_fs.h>
+#include <linux/init.h>
+#include <linux/mm.h>
+#include <linux/memcontrol.h>
+#include <linux/mm_inline.h>
+#include <linux/slab.h>
+#include <linux/random.h>
+#include <linux/reboot.h>
+#include <linux/notifier.h>
+#include <linux/kthread.h>
+
+#define __KERNEL_SYSCALLS__
+#include <linux/unistd.h>
+#include <linux/vmalloc.h>
+
+#include <linux/drbd_limits.h>
+#include "drbd_int.h"
+#include "drbd_tracing.h"
+#include "drbd_req.h" /* only for _req_mod in tl_release and tl_clear */
+
+#include "drbd_vli.h"
+
+struct after_state_chg_work {
+	struct drbd_work w;
+	union drbd_state os;
+	union drbd_state ns;
+	enum chg_state_flags flags;
+	struct completion *done;
+};
+
+int drbdd_init(struct drbd_thread *);
+int drbd_worker(struct drbd_thread *);
+int drbd_asender(struct drbd_thread *);
+
+int drbd_init(void);
+static int drbd_open(struct block_device *bdev, fmode_t mode);
+static int drbd_release(struct gendisk *gd, fmode_t mode);
+static int w_after_state_ch(struct drbd_conf *mdev, struct drbd_work *w, int unused);
+static void after_state_ch(struct drbd_conf *mdev, union drbd_state os,
+			   union drbd_state ns, enum chg_state_flags flags);
+static int w_md_sync(struct drbd_conf *mdev, struct drbd_work *w, int unused);
+static void md_sync_timer_fn(unsigned long data);
+static int w_bitmap_io(struct drbd_conf *mdev, struct drbd_work *w, int unused);
+
+DEFINE_TRACE(drbd_unplug);
+DEFINE_TRACE(drbd_uuid);
+DEFINE_TRACE(drbd_ee);
+DEFINE_TRACE(drbd_packet);
+DEFINE_TRACE(drbd_md_io);
+DEFINE_TRACE(drbd_epoch);
+DEFINE_TRACE(drbd_netlink);
+DEFINE_TRACE(drbd_actlog);
+DEFINE_TRACE(drbd_bio);
+DEFINE_TRACE(_drbd_resync);
+DEFINE_TRACE(drbd_req);
+
+MODULE_AUTHOR("Philipp Reisner <phil@linbit.com>, "
+	      "Lars Ellenberg <lars@linbit.com>");
+MODULE_DESCRIPTION("drbd - Distributed Replicated Block Device v" REL_VERSION);
+MODULE_VERSION(REL_VERSION);
+MODULE_LICENSE("GPL");
+MODULE_PARM_DESC(minor_count, "Maximum number of drbd devices (1-255)");
+MODULE_ALIAS_BLOCKDEV_MAJOR(DRBD_MAJOR);
+
+#include <linux/moduleparam.h>
+/* allow_open_on_secondary */
+MODULE_PARM_DESC(allow_oos, "DONT USE!");
+/* thanks to these macros, if compiled into the kernel (not-module),
+ * this becomes the boot parameter drbd.minor_count */
+module_param(minor_count, uint, 0444);
+module_param(disable_sendpage, bool, 0644);
+module_param(allow_oos, bool, 0);
+module_param(cn_idx, uint, 0444);
+module_param(proc_details, int, 0644);
+
+#ifdef CONFIG_DRBD_FAULT_INJECTION
+int enable_faults;
+int fault_rate;
+static int fault_count;
+int fault_devs;
+/* bitmap of enabled faults */
+module_param(enable_faults, int, 0664);
+/* fault rate % value - applies to all enabled faults */
+module_param(fault_rate, int, 0664);
+/* count of faults inserted */
+module_param(fault_count, int, 0664);
+/* bitmap of devices to insert faults on */
+module_param(fault_devs, int, 0644);
+#endif
+
+/* module parameter, defined */
+unsigned int minor_count = 32;
+int disable_sendpage;
+int allow_oos;
+unsigned int cn_idx = CN_IDX_DRBD;
+int proc_details;       /* Detail level in proc drbd*/
+
+/* Module parameter for setting the user mode helper program
+ * to run. Default is /sbin/drbdadm */
+char usermode_helper[80] = "/sbin/drbdadm";
+
+module_param_string(usermode_helper, usermode_helper, sizeof(usermode_helper), 0644);
+
+/* in 2.6.x, our device mapping and config info contains our virtual gendisks
+ * as member "struct gendisk *vdisk;"
+ */
+struct drbd_conf **minor_table;
+
+struct kmem_cache *drbd_request_cache;
+struct kmem_cache *drbd_ee_cache;	/* epoch entries */
+struct kmem_cache *drbd_bm_ext_cache;	/* bitmap extents */
+struct kmem_cache *drbd_al_ext_cache;	/* activity log extents */
+mempool_t *drbd_request_mempool;
+mempool_t *drbd_ee_mempool;
+
+/* I do not use a standard mempool, because:
+   1) I want to hand out the pre-allocated objects first.
+   2) I want to be able to interrupt sleeping allocation with a signal.
+   Note: This is a single linked list, the next pointer is the private
+	 member of struct page.
+ */
+struct page *drbd_pp_pool;
+spinlock_t   drbd_pp_lock;
+int          drbd_pp_vacant;
+wait_queue_head_t drbd_pp_wait;
+
+DEFINE_RATELIMIT_STATE(drbd_ratelimit_state, 5 * HZ, 5);
+
+static struct block_device_operations drbd_ops = {
+	.owner =   THIS_MODULE,
+	.open =    drbd_open,
+	.release = drbd_release,
+};
+
+#define ARRY_SIZE(A) (sizeof(A)/sizeof(A[0]))
+
+#ifdef __CHECKER__
+/* When checking with sparse, and this is an inline function, sparse will
+   give tons of false positives. When this is a real functions sparse works.
+ */
+int _get_ldev_if_state(struct drbd_conf *mdev, enum drbd_disk_state mins)
+{
+	int io_allowed;
+
+	atomic_inc(&mdev->local_cnt);
+	io_allowed = (mdev->state.disk >= mins);
+	if (!io_allowed) {
+		if (atomic_dec_and_test(&mdev->local_cnt))
+			wake_up(&mdev->misc_wait);
+	}
+	return io_allowed;
+}
+
+#endif
+
+/**
+ * DOC: The transfer log
+ *
+ * The transfer log is a single linked list of &struct drbd_tl_epoch objects.
+ * mdev->newest_tle points to the head, mdev->oldest_tle points to the tail
+ * of the list. There is always at least one &struct drbd_tl_epoch object.
+ *
+ * Each &struct drbd_tl_epoch has a circular double linked list of requests
+ * attached.
+ */
+static int tl_init(struct drbd_conf *mdev)
+{
+	struct drbd_tl_epoch *b;
+
+	/* during device minor initialization, we may well use GFP_KERNEL */
+	b = kmalloc(sizeof(struct drbd_tl_epoch), GFP_KERNEL);
+	if (!b)
+		return 0;
+	INIT_LIST_HEAD(&b->requests);
+	INIT_LIST_HEAD(&b->w.list);
+	b->next = NULL;
+	b->br_number = 4711;
+	b->n_req = 0;
+	b->w.cb = NULL; /* if this is != NULL, we need to dec_ap_pending in tl_clear */
+
+	mdev->oldest_tle = b;
+	mdev->newest_tle = b;
+	INIT_LIST_HEAD(&mdev->out_of_sequence_requests);
+
+	mdev->tl_hash = NULL;
+	mdev->tl_hash_s = 0;
+
+	return 1;
+}
+
+static void tl_cleanup(struct drbd_conf *mdev)
+{
+	D_ASSERT(mdev->oldest_tle == mdev->newest_tle);
+	D_ASSERT(list_empty(&mdev->out_of_sequence_requests));
+	kfree(mdev->oldest_tle);
+	mdev->oldest_tle = NULL;
+	kfree(mdev->unused_spare_tle);
+	mdev->unused_spare_tle = NULL;
+	kfree(mdev->tl_hash);
+	mdev->tl_hash = NULL;
+	mdev->tl_hash_s = 0;
+}
+
+/**
+ * _tl_add_barrier() - Adds a barrier to the transfer log
+ * @mdev:	DRBD device.
+ * @new:	Barrier to be added before the current head of the TL.
+ *
+ * The caller must hold the req_lock.
+ */
+void _tl_add_barrier(struct drbd_conf *mdev, struct drbd_tl_epoch *new)
+{
+	struct drbd_tl_epoch *newest_before;
+
+	INIT_LIST_HEAD(&new->requests);
+	INIT_LIST_HEAD(&new->w.list);
+	new->w.cb = NULL; /* if this is != NULL, we need to dec_ap_pending in tl_clear */
+	new->next = NULL;
+	new->n_req = 0;
+
+	newest_before = mdev->newest_tle;
+	/* never send a barrier number == 0, because that is special-cased
+	 * when using TCQ for our write ordering code */
+	new->br_number = (newest_before->br_number+1) ?: 1;
+	if (mdev->newest_tle != new) {
+		mdev->newest_tle->next = new;
+		mdev->newest_tle = new;
+	}
+}
+
+/**
+ * tl_release() - Free or recycle the oldest &struct drbd_tl_epoch object of the TL
+ * @mdev:	DRBD device.
+ * @barrier_nr:	Expected identifier of the DRBD write barrier packet.
+ * @set_size:	Expected number of requests before that barrier.
+ *
+ * In case the passed barrier_nr or set_size does not match the oldest
+ * &struct drbd_tl_epoch objects this function will cause a termination
+ * of the connection.
+ */
+void tl_release(struct drbd_conf *mdev, unsigned int barrier_nr,
+		       unsigned int set_size)
+{
+	struct drbd_tl_epoch *b, *nob; /* next old barrier */
+	struct list_head *le, *tle;
+	struct drbd_request *r;
+
+	spin_lock_irq(&mdev->req_lock);
+
+	b = mdev->oldest_tle;
+
+	/* first some paranoia code */
+	if (b == NULL) {
+		dev_err(DEV, "BAD! BarrierAck #%u received, but no epoch in tl!?\n",
+			barrier_nr);
+		goto bail;
+	}
+	if (b->br_number != barrier_nr) {
+		dev_err(DEV, "BAD! BarrierAck #%u received, expected #%u!\n",
+			barrier_nr, b->br_number);
+		goto bail;
+	}
+	if (b->n_req != set_size) {
+		dev_err(DEV, "BAD! BarrierAck #%u received with n_req=%u, expected n_req=%u!\n",
+			barrier_nr, set_size, b->n_req);
+		goto bail;
+	}
+
+	/* Clean up list of requests processed during current epoch */
+	list_for_each_safe(le, tle, &b->requests) {
+		r = list_entry(le, struct drbd_request, tl_requests);
+		_req_mod(r, barrier_acked);
+	}
+	/* There could be requests on the list waiting for completion
+	   of the write to the local disk. To avoid corruptions of
+	   slab's data structures we have to remove the lists head.
+
+	   Also there could have been a barrier ack out of sequence, overtaking
+	   the write acks - which would be a bug and violating write ordering.
+	   To not deadlock in case we lose connection while such requests are
+	   still pending, we need some way to find them for the
+	   _req_mode(connection_lost_while_pending).
+
+	   These have been list_move'd to the out_of_sequence_requests list in
+	   _req_mod(, barrier_acked) above.
+	   */
+	list_del_init(&b->requests);
+
+	nob = b->next;
+	if (test_and_clear_bit(CREATE_BARRIER, &mdev->flags)) {
+		_tl_add_barrier(mdev, b);
+		if (nob)
+			mdev->oldest_tle = nob;
+		/* if nob == NULL b was the only barrier, and becomes the new
+		   barrier. Therefore mdev->oldest_tle points already to b */
+	} else {
+		D_ASSERT(nob != NULL);
+		mdev->oldest_tle = nob;
+		kfree(b);
+	}
+
+	spin_unlock_irq(&mdev->req_lock);
+	dec_ap_pending(mdev);
+
+	return;
+
+bail:
+	spin_unlock_irq(&mdev->req_lock);
+	drbd_force_state(mdev, NS(conn, C_PROTOCOL_ERROR));
+}
+
+
+/**
+ * tl_clear() - Clears all requests and &struct drbd_tl_epoch objects out of the TL
+ * @mdev:	DRBD device.
+ *
+ * This is called after the connection to the peer was lost. The storage covered
+ * by the requests on the transfer gets marked as our of sync. Called from the
+ * receiver thread and the worker thread.
+ */
+void tl_clear(struct drbd_conf *mdev)
+{
+	struct drbd_tl_epoch *b, *tmp;
+	struct list_head *le, *tle;
+	struct drbd_request *r;
+	int new_initial_bnr = net_random();
+
+	spin_lock_irq(&mdev->req_lock);
+
+	b = mdev->oldest_tle;
+	while (b) {
+		list_for_each_safe(le, tle, &b->requests) {
+			r = list_entry(le, struct drbd_request, tl_requests);
+			/* It would be nice to complete outside of spinlock.
+			 * But this is easier for now. */
+			_req_mod(r, connection_lost_while_pending);
+		}
+		tmp = b->next;
+
+		/* there could still be requests on that ring list,
+		 * in case local io is still pending */
+		list_del(&b->requests);
+
+		/* dec_ap_pending corresponding to queue_barrier.
+		 * the newest barrier may not have been queued yet,
+		 * in which case w.cb is still NULL. */
+		if (b->w.cb != NULL)
+			dec_ap_pending(mdev);
+
+		if (b == mdev->newest_tle) {
+			/* recycle, but reinit! */
+			D_ASSERT(tmp == NULL);
+			INIT_LIST_HEAD(&b->requests);
+			INIT_LIST_HEAD(&b->w.list);
+			b->w.cb = NULL;
+			b->br_number = new_initial_bnr;
+			b->n_req = 0;
+
+			mdev->oldest_tle = b;
+			break;
+		}
+		kfree(b);
+		b = tmp;
+	}
+
+	/* we expect this list to be empty. */
+	D_ASSERT(list_empty(&mdev->out_of_sequence_requests));
+
+	/* but just in case, clean it up anyways! */
+	list_for_each_safe(le, tle, &mdev->out_of_sequence_requests) {
+		r = list_entry(le, struct drbd_request, tl_requests);
+		/* It would be nice to complete outside of spinlock.
+		 * But this is easier for now. */
+		_req_mod(r, connection_lost_while_pending);
+	}
+
+	/* ensure bit indicating barrier is required is clear */
+	clear_bit(CREATE_BARRIER, &mdev->flags);
+
+	spin_unlock_irq(&mdev->req_lock);
+}
+
+/**
+ * cl_wide_st_chg() - TRUE if the state change is a cluster wide one
+ * @mdev:	DRBD device.
+ * @os:		old (current) state.
+ * @ns:		new (wanted) state.
+ */
+static int cl_wide_st_chg(struct drbd_conf *mdev,
+			  union drbd_state os, union drbd_state ns)
+{
+	return (os.conn >= C_CONNECTED && ns.conn >= C_CONNECTED &&
+		 ((os.role != R_PRIMARY && ns.role == R_PRIMARY) ||
+		  (os.conn != C_STARTING_SYNC_T && ns.conn == C_STARTING_SYNC_T) ||
+		  (os.conn != C_STARTING_SYNC_S && ns.conn == C_STARTING_SYNC_S) ||
+		  (os.disk != D_DISKLESS && ns.disk == D_DISKLESS))) ||
+		(os.conn >= C_CONNECTED && ns.conn == C_DISCONNECTING) ||
+		(os.conn == C_CONNECTED && ns.conn == C_VERIFY_S);
+}
+
+int drbd_change_state(struct drbd_conf *mdev, enum chg_state_flags f,
+		      union drbd_state mask, union drbd_state val)
+{
+	unsigned long flags;
+	union drbd_state os, ns;
+	int rv;
+
+	spin_lock_irqsave(&mdev->req_lock, flags);
+	os = mdev->state;
+	ns.i = (os.i & ~mask.i) | val.i;
+	rv = _drbd_set_state(mdev, ns, f, NULL);
+	ns = mdev->state;
+	spin_unlock_irqrestore(&mdev->req_lock, flags);
+
+	return rv;
+}
+
+/**
+ * drbd_force_state() - Impose a change which happens outside our control on our state
+ * @mdev:	DRBD device.
+ * @mask:	mask of state bits to change.
+ * @val:	value of new state bits.
+ */
+void drbd_force_state(struct drbd_conf *mdev,
+	union drbd_state mask, union drbd_state val)
+{
+	drbd_change_state(mdev, CS_HARD, mask, val);
+}
+
+static int is_valid_state(struct drbd_conf *mdev, union drbd_state ns);
+static int is_valid_state_transition(struct drbd_conf *,
+				     union drbd_state, union drbd_state);
+static union drbd_state sanitize_state(struct drbd_conf *mdev, union drbd_state os,
+				       union drbd_state ns, int *warn_sync_abort);
+int drbd_send_state_req(struct drbd_conf *,
+			union drbd_state, union drbd_state);
+
+static enum drbd_state_ret_codes _req_st_cond(struct drbd_conf *mdev,
+				    union drbd_state mask, union drbd_state val)
+{
+	union drbd_state os, ns;
+	unsigned long flags;
+	int rv;
+
+	if (test_and_clear_bit(CL_ST_CHG_SUCCESS, &mdev->flags))
+		return SS_CW_SUCCESS;
+
+	if (test_and_clear_bit(CL_ST_CHG_FAIL, &mdev->flags))
+		return SS_CW_FAILED_BY_PEER;
+
+	rv = 0;
+	spin_lock_irqsave(&mdev->req_lock, flags);
+	os = mdev->state;
+	ns.i = (os.i & ~mask.i) | val.i;
+	ns = sanitize_state(mdev, os, ns, NULL);
+
+	if (!cl_wide_st_chg(mdev, os, ns))
+		rv = SS_CW_NO_NEED;
+	if (!rv) {
+		rv = is_valid_state(mdev, ns);
+		if (rv == SS_SUCCESS) {
+			rv = is_valid_state_transition(mdev, ns, os);
+			if (rv == SS_SUCCESS)
+				rv = 0; /* cont waiting, otherwise fail. */
+		}
+	}
+	spin_unlock_irqrestore(&mdev->req_lock, flags);
+
+	return rv;
+}
+
+/**
+ * drbd_req_state() - Perform an eventually cluster wide state change
+ * @mdev:	DRBD device.
+ * @mask:	mask of state bits to change.
+ * @val:	value of new state bits.
+ * @f:		flags
+ *
+ * Should not be called directly, use drbd_request_state() or
+ * _drbd_request_state().
+ */
+static int drbd_req_state(struct drbd_conf *mdev,
+			  union drbd_state mask, union drbd_state val,
+			  enum chg_state_flags f)
+{
+	struct completion done;
+	unsigned long flags;
+	union drbd_state os, ns;
+	int rv;
+
+	init_completion(&done);
+
+	if (f & CS_SERIALIZE)
+		mutex_lock(&mdev->state_mutex);
+
+	spin_lock_irqsave(&mdev->req_lock, flags);
+	os = mdev->state;
+	ns.i = (os.i & ~mask.i) | val.i;
+	ns = sanitize_state(mdev, os, ns, NULL);
+
+	if (cl_wide_st_chg(mdev, os, ns)) {
+		rv = is_valid_state(mdev, ns);
+		if (rv == SS_SUCCESS)
+			rv = is_valid_state_transition(mdev, ns, os);
+		spin_unlock_irqrestore(&mdev->req_lock, flags);
+
+		if (rv < SS_SUCCESS) {
+			if (f & CS_VERBOSE)
+				print_st_err(mdev, os, ns, rv);
+			goto abort;
+		}
+
+		drbd_state_lock(mdev);
+		if (!drbd_send_state_req(mdev, mask, val)) {
+			drbd_state_unlock(mdev);
+			rv = SS_CW_FAILED_BY_PEER;
+			if (f & CS_VERBOSE)
+				print_st_err(mdev, os, ns, rv);
+			goto abort;
+		}
+
+		wait_event(mdev->state_wait,
+			(rv = _req_st_cond(mdev, mask, val)));
+
+		if (rv < SS_SUCCESS) {
+			drbd_state_unlock(mdev);
+			if (f & CS_VERBOSE)
+				print_st_err(mdev, os, ns, rv);
+			goto abort;
+		}
+		spin_lock_irqsave(&mdev->req_lock, flags);
+		os = mdev->state;
+		ns.i = (os.i & ~mask.i) | val.i;
+		rv = _drbd_set_state(mdev, ns, f, &done);
+		drbd_state_unlock(mdev);
+	} else {
+		rv = _drbd_set_state(mdev, ns, f, &done);
+	}
+
+	spin_unlock_irqrestore(&mdev->req_lock, flags);
+
+	if (f & CS_WAIT_COMPLETE && rv == SS_SUCCESS) {
+		D_ASSERT(current != mdev->worker.task);
+		wait_for_completion(&done);
+	}
+
+abort:
+	if (f & CS_SERIALIZE)
+		mutex_unlock(&mdev->state_mutex);
+
+	return rv;
+}
+
+/**
+ * _drbd_request_state() - Request a state change (with flags)
+ * @mdev:	DRBD device.
+ * @mask:	mask of state bits to change.
+ * @val:	value of new state bits.
+ * @f:		flags
+ *
+ * Cousin of drbd_request_state(), useful with the CS_WAIT_COMPLETE
+ * flag, or when logging of failed state change requests is not desired.
+ */
+int _drbd_request_state(struct drbd_conf *mdev,	union drbd_state mask,
+			union drbd_state val,	enum chg_state_flags f)
+{
+	int rv;
+
+	wait_event(mdev->state_wait,
+		   (rv = drbd_req_state(mdev, mask, val, f)) != SS_IN_TRANSIENT_STATE);
+
+	return rv;
+}
+
+static void print_st(struct drbd_conf *mdev, char *name, union drbd_state ns)
+{
+	dev_err(DEV, " %s = { cs:%s ro:%s/%s ds:%s/%s %c%c%c%c }\n",
+	    name,
+	    drbd_conn_str(ns.conn),
+	    drbd_role_str(ns.role),
+	    drbd_role_str(ns.peer),
+	    drbd_disk_str(ns.disk),
+	    drbd_disk_str(ns.pdsk),
+	    ns.susp ? 's' : 'r',
+	    ns.aftr_isp ? 'a' : '-',
+	    ns.peer_isp ? 'p' : '-',
+	    ns.user_isp ? 'u' : '-'
+	    );
+}
+
+void print_st_err(struct drbd_conf *mdev,
+	union drbd_state os, union drbd_state ns, int err)
+{
+	if (err == SS_IN_TRANSIENT_STATE)
+		return;
+	dev_err(DEV, "State change failed: %s\n", drbd_set_st_err_str(err));
+	print_st(mdev, " state", os);
+	print_st(mdev, "wanted", ns);
+}
+
+
+#define drbd_peer_str drbd_role_str
+#define drbd_pdsk_str drbd_disk_str
+
+#define drbd_susp_str(A)     ((A) ? "1" : "0")
+#define drbd_aftr_isp_str(A) ((A) ? "1" : "0")
+#define drbd_peer_isp_str(A) ((A) ? "1" : "0")
+#define drbd_user_isp_str(A) ((A) ? "1" : "0")
+
+#define PSC(A) \
+	({ if (ns.A != os.A) { \
+		pbp += sprintf(pbp, #A "( %s -> %s ) ", \
+			      drbd_##A##_str(os.A), \
+			      drbd_##A##_str(ns.A)); \
+	} })
+
+/**
+ * is_valid_state() - Returns an SS_ error code if ns is not valid
+ * @mdev:	DRBD device.
+ * @ns:		State to consider.
+ */
+static int is_valid_state(struct drbd_conf *mdev, union drbd_state ns)
+{
+	/* See drbd_state_sw_errors in drbd_strings.c */
+
+	enum drbd_fencing_p fp;
+	int rv = SS_SUCCESS;
+
+	fp = FP_DONT_CARE;
+	if (get_ldev(mdev)) {
+		fp = mdev->ldev->dc.fencing;
+		put_ldev(mdev);
+	}
+
+	if (get_net_conf(mdev)) {
+		if (!mdev->net_conf->two_primaries &&
+		    ns.role == R_PRIMARY && ns.peer == R_PRIMARY)
+			rv = SS_TWO_PRIMARIES;
+		put_net_conf(mdev);
+	}
+
+	if (rv <= 0)
+		/* already found a reason to abort */;
+	else if (ns.role == R_SECONDARY && mdev->open_cnt)
+		rv = SS_DEVICE_IN_USE;
+
+	else if (ns.role == R_PRIMARY && ns.conn < C_CONNECTED && ns.disk < D_UP_TO_DATE)
+		rv = SS_NO_UP_TO_DATE_DISK;
+
+	else if (fp >= FP_RESOURCE &&
+		 ns.role == R_PRIMARY && ns.conn < C_CONNECTED && ns.pdsk >= D_UNKNOWN)
+		rv = SS_PRIMARY_NOP;
+
+	else if (ns.role == R_PRIMARY && ns.disk <= D_INCONSISTENT && ns.pdsk <= D_INCONSISTENT)
+		rv = SS_NO_UP_TO_DATE_DISK;
+
+	else if (ns.conn > C_CONNECTED && ns.disk < D_INCONSISTENT)
+		rv = SS_NO_LOCAL_DISK;
+
+	else if (ns.conn > C_CONNECTED && ns.pdsk < D_INCONSISTENT)
+		rv = SS_NO_REMOTE_DISK;
+
+	else if ((ns.conn == C_CONNECTED ||
+		  ns.conn == C_WF_BITMAP_S ||
+		  ns.conn == C_SYNC_SOURCE ||
+		  ns.conn == C_PAUSED_SYNC_S) &&
+		  ns.disk == D_OUTDATED)
+		rv = SS_CONNECTED_OUTDATES;
+
+	else if ((ns.conn == C_VERIFY_S || ns.conn == C_VERIFY_T) &&
+		 (mdev->sync_conf.verify_alg[0] == 0))
+		rv = SS_NO_VERIFY_ALG;
+
+	else if ((ns.conn == C_VERIFY_S || ns.conn == C_VERIFY_T) &&
+		  mdev->agreed_pro_version < 88)
+		rv = SS_NOT_SUPPORTED;
+
+	return rv;
+}
+
+/**
+ * is_valid_state_transition() - Returns an SS_ error code if the state transition is not possible
+ * @mdev:	DRBD device.
+ * @ns:		new state.
+ * @os:		old state.
+ */
+static int is_valid_state_transition(struct drbd_conf *mdev,
+				     union drbd_state ns, union drbd_state os)
+{
+	int rv = SS_SUCCESS;
+
+	if ((ns.conn == C_STARTING_SYNC_T || ns.conn == C_STARTING_SYNC_S) &&
+	    os.conn > C_CONNECTED)
+		rv = SS_RESYNC_RUNNING;
+
+	if (ns.conn == C_DISCONNECTING && os.conn == C_STANDALONE)
+		rv = SS_ALREADY_STANDALONE;
+
+	if (ns.disk > D_ATTACHING && os.disk == D_DISKLESS)
+		rv = SS_IS_DISKLESS;
+
+	if (ns.conn == C_WF_CONNECTION && os.conn < C_UNCONNECTED)
+		rv = SS_NO_NET_CONFIG;
+
+	if (ns.disk == D_OUTDATED && os.disk < D_OUTDATED && os.disk != D_ATTACHING)
+		rv = SS_LOWER_THAN_OUTDATED;
+
+	if (ns.conn == C_DISCONNECTING && os.conn == C_UNCONNECTED)
+		rv = SS_IN_TRANSIENT_STATE;
+
+	if (ns.conn == os.conn && ns.conn == C_WF_REPORT_PARAMS)
+		rv = SS_IN_TRANSIENT_STATE;
+
+	if ((ns.conn == C_VERIFY_S || ns.conn == C_VERIFY_T) && os.conn < C_CONNECTED)
+		rv = SS_NEED_CONNECTION;
+
+	if ((ns.conn == C_VERIFY_S || ns.conn == C_VERIFY_T) &&
+	    ns.conn != os.conn && os.conn > C_CONNECTED)
+		rv = SS_RESYNC_RUNNING;
+
+	if ((ns.conn == C_STARTING_SYNC_S || ns.conn == C_STARTING_SYNC_T) &&
+	    os.conn < C_CONNECTED)
+		rv = SS_NEED_CONNECTION;
+
+	return rv;
+}
+
+/**
+ * sanitize_state() - Resolves implicitly necessary additional changes to a state transition
+ * @mdev:	DRBD device.
+ * @os:		old state.
+ * @ns:		new state.
+ * @warn_sync_abort:
+ *
+ * When we loose connection, we have to set the state of the peers disk (pdsk)
+ * to D_UNKNOWN. This rule and many more along those lines are in this function.
+ */
+static union drbd_state sanitize_state(struct drbd_conf *mdev, union drbd_state os,
+				       union drbd_state ns, int *warn_sync_abort)
+{
+	enum drbd_fencing_p fp;
+
+	fp = FP_DONT_CARE;
+	if (get_ldev(mdev)) {
+		fp = mdev->ldev->dc.fencing;
+		put_ldev(mdev);
+	}
+
+	/* Disallow Network errors to configure a device's network part */
+	if ((ns.conn >= C_TIMEOUT && ns.conn <= C_TEAR_DOWN) &&
+	    os.conn <= C_DISCONNECTING)
+		ns.conn = os.conn;
+
+	/* After a network error (+C_TEAR_DOWN) only C_UNCONNECTED or C_DISCONNECTING can follow */
+	if (os.conn >= C_TIMEOUT && os.conn <= C_TEAR_DOWN &&
+	    ns.conn != C_UNCONNECTED && ns.conn != C_DISCONNECTING)
+		ns.conn = os.conn;
+
+	/* After C_DISCONNECTING only C_STANDALONE may follow */
+	if (os.conn == C_DISCONNECTING && ns.conn != C_STANDALONE)
+		ns.conn = os.conn;
+
+	if (ns.conn < C_CONNECTED) {
+		ns.peer_isp = 0;
+		ns.peer = R_UNKNOWN;
+		if (ns.pdsk > D_UNKNOWN || ns.pdsk < D_INCONSISTENT)
+			ns.pdsk = D_UNKNOWN;
+	}
+
+	/* Clear the aftr_isp when becoming unconfigured */
+	if (ns.conn == C_STANDALONE && ns.disk == D_DISKLESS && ns.role == R_SECONDARY)
+		ns.aftr_isp = 0;
+
+	if (ns.conn <= C_DISCONNECTING && ns.disk == D_DISKLESS)
+		ns.pdsk = D_UNKNOWN;
+
+	/* Abort resync if a disk fails/detaches */
+	if (os.conn > C_CONNECTED && ns.conn > C_CONNECTED &&
+	    (ns.disk <= D_FAILED || ns.pdsk <= D_FAILED)) {
+		if (warn_sync_abort)
+			*warn_sync_abort = 1;
+		ns.conn = C_CONNECTED;
+	}
+
+	if (ns.conn >= C_CONNECTED &&
+	    ((ns.disk == D_CONSISTENT || ns.disk == D_OUTDATED) ||
+	     (ns.disk == D_NEGOTIATING && ns.conn == C_WF_BITMAP_T))) {
+		switch (ns.conn) {
+		case C_WF_BITMAP_T:
+		case C_PAUSED_SYNC_T:
+			ns.disk = D_OUTDATED;
+			break;
+		case C_CONNECTED:
+		case C_WF_BITMAP_S:
+		case C_SYNC_SOURCE:
+		case C_PAUSED_SYNC_S:
+			ns.disk = D_UP_TO_DATE;
+			break;
+		case C_SYNC_TARGET:
+			ns.disk = D_INCONSISTENT;
+			dev_warn(DEV, "Implicitly set disk state Inconsistent!\n");
+			break;
+		}
+		if (os.disk == D_OUTDATED && ns.disk == D_UP_TO_DATE)
+			dev_warn(DEV, "Implicitly set disk from Outdated to UpToDate\n");
+	}
+
+	if (ns.conn >= C_CONNECTED &&
+	    (ns.pdsk == D_CONSISTENT || ns.pdsk == D_OUTDATED)) {
+		switch (ns.conn) {
+		case C_CONNECTED:
+		case C_WF_BITMAP_T:
+		case C_PAUSED_SYNC_T:
+		case C_SYNC_TARGET:
+			ns.pdsk = D_UP_TO_DATE;
+			break;
+		case C_WF_BITMAP_S:
+		case C_PAUSED_SYNC_S:
+			ns.pdsk = D_OUTDATED;
+			break;
+		case C_SYNC_SOURCE:
+			ns.pdsk = D_INCONSISTENT;
+			dev_warn(DEV, "Implicitly set pdsk Inconsistent!\n");
+			break;
+		}
+		if (os.pdsk == D_OUTDATED && ns.pdsk == D_UP_TO_DATE)
+			dev_warn(DEV, "Implicitly set pdsk from Outdated to UpToDate\n");
+	}
+
+	/* Connection breaks down before we finished "Negotiating" */
+	if (ns.conn < C_CONNECTED && ns.disk == D_NEGOTIATING &&
+	    get_ldev_if_state(mdev, D_NEGOTIATING)) {
+		if (mdev->ed_uuid == mdev->ldev->md.uuid[UI_CURRENT]) {
+			ns.disk = mdev->new_state_tmp.disk;
+			ns.pdsk = mdev->new_state_tmp.pdsk;
+		} else {
+			dev_alert(DEV, "Connection lost while negotiating, no data!\n");
+			ns.disk = D_DISKLESS;
+			ns.pdsk = D_UNKNOWN;
+		}
+		put_ldev(mdev);
+	}
+
+	if (fp == FP_STONITH &&
+	    (ns.role == R_PRIMARY &&
+	     ns.conn < C_CONNECTED &&
+	     ns.pdsk > D_OUTDATED))
+			ns.susp = 1;
+
+	if (ns.aftr_isp || ns.peer_isp || ns.user_isp) {
+		if (ns.conn == C_SYNC_SOURCE)
+			ns.conn = C_PAUSED_SYNC_S;
+		if (ns.conn == C_SYNC_TARGET)
+			ns.conn = C_PAUSED_SYNC_T;
+	} else {
+		if (ns.conn == C_PAUSED_SYNC_S)
+			ns.conn = C_SYNC_SOURCE;
+		if (ns.conn == C_PAUSED_SYNC_T)
+			ns.conn = C_SYNC_TARGET;
+	}
+
+	return ns;
+}
+
+/* helper for __drbd_set_state */
+static void set_ov_position(struct drbd_conf *mdev, enum drbd_conns cs)
+{
+	if (cs == C_VERIFY_T) {
+		/* starting online verify from an arbitrary position
+		 * does not fit well into the existing protocol.
+		 * on C_VERIFY_T, we initialize ov_left and friends
+		 * implicitly in receive_DataRequest once the
+		 * first P_OV_REQUEST is received */
+		mdev->ov_start_sector = ~(sector_t)0;
+	} else {
+		unsigned long bit = BM_SECT_TO_BIT(mdev->ov_start_sector);
+		if (bit >= mdev->rs_total)
+			mdev->ov_start_sector =
+				BM_BIT_TO_SECT(mdev->rs_total - 1);
+		mdev->ov_position = mdev->ov_start_sector;
+	}
+}
+
+/**
+ * __drbd_set_state() - Set a new DRBD state
+ * @mdev:	DRBD device.
+ * @ns:		new state.
+ * @flags:	Flags
+ * @done:	Optional completion, that will get completed after the after_state_ch() finished
+ *
+ * Caller needs to hold req_lock, and global_state_lock. Do not call directly.
+ */
+int __drbd_set_state(struct drbd_conf *mdev,
+		    union drbd_state ns, enum chg_state_flags flags,
+		    struct completion *done)
+{
+	union drbd_state os;
+	int rv = SS_SUCCESS;
+	int warn_sync_abort = 0;
+	struct after_state_chg_work *ascw;
+
+	os = mdev->state;
+
+	ns = sanitize_state(mdev, os, ns, &warn_sync_abort);
+
+	if (ns.i == os.i)
+		return SS_NOTHING_TO_DO;
+
+	if (!(flags & CS_HARD)) {
+		/*  pre-state-change checks ; only look at ns  */
+		/* See drbd_state_sw_errors in drbd_strings.c */
+
+		rv = is_valid_state(mdev, ns);
+		if (rv < SS_SUCCESS) {
+			/* If the old state was illegal as well, then let
+			   this happen...*/
+
+			if (is_valid_state(mdev, os) == rv) {
+				dev_err(DEV, "Considering state change from bad state. "
+				    "Error would be: '%s'\n",
+				    drbd_set_st_err_str(rv));
+				print_st(mdev, "old", os);
+				print_st(mdev, "new", ns);
+				rv = is_valid_state_transition(mdev, ns, os);
+			}
+		} else
+			rv = is_valid_state_transition(mdev, ns, os);
+	}
+
+	if (rv < SS_SUCCESS) {
+		if (flags & CS_VERBOSE)
+			print_st_err(mdev, os, ns, rv);
+		return rv;
+	}
+
+	if (warn_sync_abort)
+		dev_warn(DEV, "Resync aborted.\n");
+
+	{
+		char *pbp, pb[300];
+		pbp = pb;
+		*pbp = 0;
+		PSC(role);
+		PSC(peer);
+		PSC(conn);
+		PSC(disk);
+		PSC(pdsk);
+		PSC(susp);
+		PSC(aftr_isp);
+		PSC(peer_isp);
+		PSC(user_isp);
+		dev_info(DEV, "%s\n", pb);
+	}
+
+	/* solve the race between becoming unconfigured,
+	 * worker doing the cleanup, and
+	 * admin reconfiguring us:
+	 * on (re)configure, first set CONFIG_PENDING,
+	 * then wait for a potentially exiting worker,
+	 * start the worker, and schedule one no_op.
+	 * then proceed with configuration.
+	 */
+	if (ns.disk == D_DISKLESS &&
+	    ns.conn == C_STANDALONE &&
+	    ns.role == R_SECONDARY &&
+	    !test_and_set_bit(CONFIG_PENDING, &mdev->flags))
+		set_bit(DEVICE_DYING, &mdev->flags);
+
+	mdev->state.i = ns.i;
+	wake_up(&mdev->misc_wait);
+	wake_up(&mdev->state_wait);
+
+	/*   post-state-change actions   */
+	if (os.conn >= C_SYNC_SOURCE   && ns.conn <= C_CONNECTED) {
+		set_bit(STOP_SYNC_TIMER, &mdev->flags);
+		mod_timer(&mdev->resync_timer, jiffies);
+	}
+
+	/* aborted verify run. log the last position */
+	if ((os.conn == C_VERIFY_S || os.conn == C_VERIFY_T) &&
+	    ns.conn < C_CONNECTED) {
+		mdev->ov_start_sector =
+			BM_BIT_TO_SECT(mdev->rs_total - mdev->ov_left);
+		dev_info(DEV, "Online Verify reached sector %llu\n",
+			(unsigned long long)mdev->ov_start_sector);
+	}
+
+	if ((os.conn == C_PAUSED_SYNC_T || os.conn == C_PAUSED_SYNC_S) &&
+	    (ns.conn == C_SYNC_TARGET  || ns.conn == C_SYNC_SOURCE)) {
+		dev_info(DEV, "Syncer continues.\n");
+		mdev->rs_paused += (long)jiffies-(long)mdev->rs_mark_time;
+		if (ns.conn == C_SYNC_TARGET) {
+			if (!test_and_clear_bit(STOP_SYNC_TIMER, &mdev->flags))
+				mod_timer(&mdev->resync_timer, jiffies);
+			/* This if (!test_bit) is only needed for the case
+			   that a device that has ceased to used its timer,
+			   i.e. it is already in drbd_resync_finished() gets
+			   paused and resumed. */
+		}
+	}
+
+	if ((os.conn == C_SYNC_TARGET  || os.conn == C_SYNC_SOURCE) &&
+	    (ns.conn == C_PAUSED_SYNC_T || ns.conn == C_PAUSED_SYNC_S)) {
+		dev_info(DEV, "Resync suspended\n");
+		mdev->rs_mark_time = jiffies;
+		if (ns.conn == C_PAUSED_SYNC_T)
+			set_bit(STOP_SYNC_TIMER, &mdev->flags);
+	}
+
+	if (os.conn == C_CONNECTED &&
+	    (ns.conn == C_VERIFY_S || ns.conn == C_VERIFY_T)) {
+		mdev->ov_position = 0;
+		mdev->rs_total =
+		mdev->rs_mark_left = drbd_bm_bits(mdev);
+		if (mdev->agreed_pro_version >= 90)
+			set_ov_position(mdev, ns.conn);
+		else
+			mdev->ov_start_sector = 0;
+		mdev->ov_left = mdev->rs_total
+			      - BM_SECT_TO_BIT(mdev->ov_position);
+		mdev->rs_start     =
+		mdev->rs_mark_time = jiffies;
+		mdev->ov_last_oos_size = 0;
+		mdev->ov_last_oos_start = 0;
+
+		if (ns.conn == C_VERIFY_S) {
+			dev_info(DEV, "Starting Online Verify from sector %llu\n",
+					(unsigned long long)mdev->ov_position);
+			mod_timer(&mdev->resync_timer, jiffies);
+		}
+	}
+
+	if (get_ldev(mdev)) {
+		u32 mdf = mdev->ldev->md.flags & ~(MDF_CONSISTENT|MDF_PRIMARY_IND|
+						 MDF_CONNECTED_IND|MDF_WAS_UP_TO_DATE|
+						 MDF_PEER_OUT_DATED|MDF_CRASHED_PRIMARY);
+
+		if (test_bit(CRASHED_PRIMARY, &mdev->flags))
+			mdf |= MDF_CRASHED_PRIMARY;
+		if (mdev->state.role == R_PRIMARY ||
+		    (mdev->state.pdsk < D_INCONSISTENT && mdev->state.peer == R_PRIMARY))
+			mdf |= MDF_PRIMARY_IND;
+		if (mdev->state.conn > C_WF_REPORT_PARAMS)
+			mdf |= MDF_CONNECTED_IND;
+		if (mdev->state.disk > D_INCONSISTENT)
+			mdf |= MDF_CONSISTENT;
+		if (mdev->state.disk > D_OUTDATED)
+			mdf |= MDF_WAS_UP_TO_DATE;
+		if (mdev->state.pdsk <= D_OUTDATED && mdev->state.pdsk >= D_INCONSISTENT)
+			mdf |= MDF_PEER_OUT_DATED;
+		if (mdf != mdev->ldev->md.flags) {
+			mdev->ldev->md.flags = mdf;
+			drbd_md_mark_dirty(mdev);
+		}
+		if (os.disk < D_CONSISTENT && ns.disk >= D_CONSISTENT)
+			drbd_set_ed_uuid(mdev, mdev->ldev->md.uuid[UI_CURRENT]);
+		put_ldev(mdev);
+	}
+
+	/* Peer was forced D_UP_TO_DATE & R_PRIMARY, consider to resync */
+	if (os.disk == D_INCONSISTENT && os.pdsk == D_INCONSISTENT &&
+	    os.peer == R_SECONDARY && ns.peer == R_PRIMARY)
+		set_bit(CONSIDER_RESYNC, &mdev->flags);
+
+	/* Receiver should clean up itself */
+	if (os.conn != C_DISCONNECTING && ns.conn == C_DISCONNECTING)
+		drbd_thread_stop_nowait(&mdev->receiver);
+
+	/* Now the receiver finished cleaning up itself, it should die */
+	if (os.conn != C_STANDALONE && ns.conn == C_STANDALONE)
+		drbd_thread_stop_nowait(&mdev->receiver);
+
+	/* Upon network failure, we need to restart the receiver. */
+	if (os.conn > C_TEAR_DOWN &&
+	    ns.conn <= C_TEAR_DOWN && ns.conn >= C_TIMEOUT)
+		drbd_thread_restart_nowait(&mdev->receiver);
+
+	ascw = kmalloc(sizeof(*ascw), GFP_ATOMIC);
+	if (ascw) {
+		ascw->os = os;
+		ascw->ns = ns;
+		ascw->flags = flags;
+		ascw->w.cb = w_after_state_ch;
+		ascw->done = done;
+		drbd_queue_work(&mdev->data.work, &ascw->w);
+	} else {
+		dev_warn(DEV, "Could not kmalloc an ascw\n");
+	}
+
+	return rv;
+}
+
+static int w_after_state_ch(struct drbd_conf *mdev, struct drbd_work *w, int unused)
+{
+	struct after_state_chg_work *ascw =
+		container_of(w, struct after_state_chg_work, w);
+	after_state_ch(mdev, ascw->os, ascw->ns, ascw->flags);
+	if (ascw->flags & CS_WAIT_COMPLETE) {
+		D_ASSERT(ascw->done != NULL);
+		complete(ascw->done);
+	}
+	kfree(ascw);
+
+	return 1;
+}
+
+static void abw_start_sync(struct drbd_conf *mdev, int rv)
+{
+	if (rv) {
+		dev_err(DEV, "Writing the bitmap failed not starting resync.\n");
+		_drbd_request_state(mdev, NS(conn, C_CONNECTED), CS_VERBOSE);
+		return;
+	}
+
+	switch (mdev->state.conn) {
+	case C_STARTING_SYNC_T:
+		_drbd_request_state(mdev, NS(conn, C_WF_SYNC_UUID), CS_VERBOSE);
+		break;
+	case C_STARTING_SYNC_S:
+		drbd_start_resync(mdev, C_SYNC_SOURCE);
+		break;
+	}
+}
+
+/**
+ * after_state_ch() - Perform after state change actions that may sleep
+ * @mdev:	DRBD device.
+ * @os:		old state.
+ * @ns:		new state.
+ * @flags:	Flags
+ */
+static void after_state_ch(struct drbd_conf *mdev, union drbd_state os,
+			   union drbd_state ns, enum chg_state_flags flags)
+{
+	enum drbd_fencing_p fp;
+
+	if (os.conn != C_CONNECTED && ns.conn == C_CONNECTED) {
+		clear_bit(CRASHED_PRIMARY, &mdev->flags);
+		if (mdev->p_uuid)
+			mdev->p_uuid[UI_FLAGS] &= ~((u64)2);
+	}
+
+	fp = FP_DONT_CARE;
+	if (get_ldev(mdev)) {
+		fp = mdev->ldev->dc.fencing;
+		put_ldev(mdev);
+	}
+
+	/* Inform userspace about the change... */
+	drbd_bcast_state(mdev, ns);
+
+	if (!(os.role == R_PRIMARY && os.disk < D_UP_TO_DATE && os.pdsk < D_UP_TO_DATE) &&
+	    (ns.role == R_PRIMARY && ns.disk < D_UP_TO_DATE && ns.pdsk < D_UP_TO_DATE))
+		drbd_khelper(mdev, "pri-on-incon-degr");
+
+	/* Here we have the actions that are performed after a
+	   state change. This function might sleep */
+
+	if (fp == FP_STONITH && ns.susp) {
+		/* case1: The outdate peer handler is successful:
+		 * case2: The connection was established again: */
+		if ((os.pdsk > D_OUTDATED  && ns.pdsk <= D_OUTDATED) ||
+		    (os.conn < C_CONNECTED && ns.conn >= C_CONNECTED)) {
+			tl_clear(mdev);
+			spin_lock_irq(&mdev->req_lock);
+			_drbd_set_state(_NS(mdev, susp, 0), CS_VERBOSE, NULL);
+			spin_unlock_irq(&mdev->req_lock);
+		}
+	}
+	/* Do not change the order of the if above and the two below... */
+	if (os.pdsk == D_DISKLESS && ns.pdsk > D_DISKLESS) {      /* attach on the peer */
+		drbd_send_uuids(mdev);
+		drbd_send_state(mdev);
+	}
+	if (os.conn != C_WF_BITMAP_S && ns.conn == C_WF_BITMAP_S)
+		drbd_queue_bitmap_io(mdev, &drbd_send_bitmap, NULL, "send_bitmap (WFBitMapS)");
+
+	/* Lost contact to peer's copy of the data */
+	if ((os.pdsk >= D_INCONSISTENT &&
+	     os.pdsk != D_UNKNOWN &&
+	     os.pdsk != D_OUTDATED)
+	&&  (ns.pdsk < D_INCONSISTENT ||
+	     ns.pdsk == D_UNKNOWN ||
+	     ns.pdsk == D_OUTDATED)) {
+		kfree(mdev->p_uuid);
+		mdev->p_uuid = NULL;
+		if (get_ldev(mdev)) {
+			if ((ns.role == R_PRIMARY || ns.peer == R_PRIMARY) &&
+			    mdev->ldev->md.uuid[UI_BITMAP] == 0 && ns.disk >= D_UP_TO_DATE) {
+				drbd_uuid_new_current(mdev);
+				drbd_send_uuids(mdev);
+			}
+			put_ldev(mdev);
+		}
+	}
+
+	if (ns.pdsk < D_INCONSISTENT && get_ldev(mdev)) {
+		if (ns.peer == R_PRIMARY && mdev->ldev->md.uuid[UI_BITMAP] == 0)
+			drbd_uuid_new_current(mdev);
+
+		/* D_DISKLESS Peer becomes secondary */
+		if (os.peer == R_PRIMARY && ns.peer == R_SECONDARY)
+			drbd_al_to_on_disk_bm(mdev);
+		put_ldev(mdev);
+	}
+
+	/* Last part of the attaching process ... */
+	if (ns.conn >= C_CONNECTED &&
+	    os.disk == D_ATTACHING && ns.disk == D_NEGOTIATING) {
+		kfree(mdev->p_uuid); /* We expect to receive up-to-date UUIDs soon. */
+		mdev->p_uuid = NULL; /* ...to not use the old ones in the mean time */
+		drbd_send_sizes(mdev, 0);  /* to start sync... */
+		drbd_send_uuids(mdev);
+		drbd_send_state(mdev);
+	}
+
+	/* We want to pause/continue resync, tell peer. */
+	if (ns.conn >= C_CONNECTED &&
+	     ((os.aftr_isp != ns.aftr_isp) ||
+	      (os.user_isp != ns.user_isp)))
+		drbd_send_state(mdev);
+
+	/* In case one of the isp bits got set, suspend other devices. */
+	if ((!os.aftr_isp && !os.peer_isp && !os.user_isp) &&
+	    (ns.aftr_isp || ns.peer_isp || ns.user_isp))
+		suspend_other_sg(mdev);
+
+	/* Make sure the peer gets informed about eventual state
+	   changes (ISP bits) while we were in WFReportParams. */
+	if (os.conn == C_WF_REPORT_PARAMS && ns.conn >= C_CONNECTED)
+		drbd_send_state(mdev);
+
+	/* We are in the progress to start a full sync... */
+	if ((os.conn != C_STARTING_SYNC_T && ns.conn == C_STARTING_SYNC_T) ||
+	    (os.conn != C_STARTING_SYNC_S && ns.conn == C_STARTING_SYNC_S))
+		drbd_queue_bitmap_io(mdev, &drbd_bmio_set_n_write, &abw_start_sync, "set_n_write from StartingSync");
+
+	/* We are invalidating our self... */
+	if (os.conn < C_CONNECTED && ns.conn < C_CONNECTED &&
+	    os.disk > D_INCONSISTENT && ns.disk == D_INCONSISTENT)
+		drbd_queue_bitmap_io(mdev, &drbd_bmio_set_n_write, NULL, "set_n_write from invalidate");
+
+	if (os.disk > D_FAILED && ns.disk == D_FAILED) {
+		enum drbd_io_error_p eh;
+
+		eh = EP_PASS_ON;
+		if (get_ldev_if_state(mdev, D_FAILED)) {
+			eh = mdev->ldev->dc.on_io_error;
+			put_ldev(mdev);
+		}
+
+		drbd_rs_cancel_all(mdev);
+		/* since get_ldev() only works as long as disk>=D_INCONSISTENT,
+		   and it is D_DISKLESS here, local_cnt can only go down, it can
+		   not increase... It will reach zero */
+		wait_event(mdev->misc_wait, !atomic_read(&mdev->local_cnt));
+		mdev->rs_total = 0;
+		mdev->rs_failed = 0;
+		atomic_set(&mdev->rs_pending_cnt, 0);
+
+		spin_lock_irq(&mdev->req_lock);
+		_drbd_set_state(_NS(mdev, disk, D_DISKLESS), CS_HARD, NULL);
+		spin_unlock_irq(&mdev->req_lock);
+
+		if (eh == EP_CALL_HELPER)
+			drbd_khelper(mdev, "local-io-error");
+	}
+
+	if (os.disk > D_DISKLESS && ns.disk == D_DISKLESS) {
+
+		if (os.disk == D_FAILED) /* && ns.disk == D_DISKLESS*/ {
+			if (drbd_send_state(mdev))
+				dev_warn(DEV, "Notified peer that my disk is broken.\n");
+			else
+				dev_err(DEV, "Sending state in drbd_io_error() failed\n");
+		}
+
+		lc_destroy(mdev->resync);
+		mdev->resync = NULL;
+		lc_destroy(mdev->act_log);
+		mdev->act_log = NULL;
+		__no_warn(local,
+			drbd_free_bc(mdev->ldev);
+			mdev->ldev = NULL;);
+
+		if (mdev->md_io_tmpp)
+			__free_page(mdev->md_io_tmpp);
+	}
+
+	/* Disks got bigger while they were detached */
+	if (ns.disk > D_NEGOTIATING && ns.pdsk > D_NEGOTIATING &&
+	    test_and_clear_bit(RESYNC_AFTER_NEG, &mdev->flags)) {
+		if (ns.conn == C_CONNECTED)
+			resync_after_online_grow(mdev);
+	}
+
+	/* A resync finished or aborted, wake paused devices... */
+	if ((os.conn > C_CONNECTED && ns.conn <= C_CONNECTED) ||
+	    (os.peer_isp && !ns.peer_isp) ||
+	    (os.user_isp && !ns.user_isp))
+		resume_next_sg(mdev);
+
+	/* Upon network connection, we need to start the receiver */
+	if (os.conn == C_STANDALONE && ns.conn == C_UNCONNECTED)
+		drbd_thread_start(&mdev->receiver);
+
+	/* Terminate worker thread if we are unconfigured - it will be
+	   restarted as needed... */
+	if (ns.disk == D_DISKLESS &&
+	    ns.conn == C_STANDALONE &&
+	    ns.role == R_SECONDARY) {
+		if (os.aftr_isp != ns.aftr_isp)
+			resume_next_sg(mdev);
+		/* set in __drbd_set_state, unless CONFIG_PENDING was set */
+		if (test_bit(DEVICE_DYING, &mdev->flags))
+			drbd_thread_stop_nowait(&mdev->worker);
+	}
+
+	drbd_md_sync(mdev);
+}
+
+
+static int drbd_thread_setup(void *arg)
+{
+	struct drbd_thread *thi = (struct drbd_thread *) arg;
+	struct drbd_conf *mdev = thi->mdev;
+	unsigned long flags;
+	int retval;
+
+restart:
+	retval = thi->function(thi);
+
+	spin_lock_irqsave(&thi->t_lock, flags);
+
+	/* if the receiver has been "Exiting", the last thing it did
+	 * was set the conn state to "StandAlone",
+	 * if now a re-connect request comes in, conn state goes C_UNCONNECTED,
+	 * and receiver thread will be "started".
+	 * drbd_thread_start needs to set "Restarting" in that case.
+	 * t_state check and assignment needs to be within the same spinlock,
+	 * so either thread_start sees Exiting, and can remap to Restarting,
+	 * or thread_start see None, and can proceed as normal.
+	 */
+
+	if (thi->t_state == Restarting) {
+		dev_info(DEV, "Restarting %s\n", current->comm);
+		thi->t_state = Running;
+		spin_unlock_irqrestore(&thi->t_lock, flags);
+		goto restart;
+	}
+
+	thi->task = NULL;
+	thi->t_state = None;
+	smp_mb();
+	complete(&thi->stop);
+	spin_unlock_irqrestore(&thi->t_lock, flags);
+
+	dev_info(DEV, "Terminating %s\n", current->comm);
+
+	/* Release mod reference taken when thread was started */
+	module_put(THIS_MODULE);
+	return retval;
+}
+
+static void drbd_thread_init(struct drbd_conf *mdev, struct drbd_thread *thi,
+		      int (*func) (struct drbd_thread *))
+{
+	spin_lock_init(&thi->t_lock);
+	thi->task    = NULL;
+	thi->t_state = None;
+	thi->function = func;
+	thi->mdev = mdev;
+}
+
+int drbd_thread_start(struct drbd_thread *thi)
+{
+	struct drbd_conf *mdev = thi->mdev;
+	struct task_struct *nt;
+	unsigned long flags;
+
+	const char *me =
+		thi == &mdev->receiver ? "receiver" :
+		thi == &mdev->asender  ? "asender"  :
+		thi == &mdev->worker   ? "worker"   : "NONSENSE";
+
+	/* is used from state engine doing drbd_thread_stop_nowait,
+	 * while holding the req lock irqsave */
+	spin_lock_irqsave(&thi->t_lock, flags);
+
+	switch (thi->t_state) {
+	case None:
+		dev_info(DEV, "Starting %s thread (from %s [%d])\n",
+				me, current->comm, current->pid);
+
+		/* Get ref on module for thread - this is released when thread exits */
+		if (!try_module_get(THIS_MODULE)) {
+			dev_err(DEV, "Failed to get module reference in drbd_thread_start\n");
+			spin_unlock_irqrestore(&thi->t_lock, flags);
+			return FALSE;
+		}
+
+		init_completion(&thi->stop);
+		D_ASSERT(thi->task == NULL);
+		thi->reset_cpu_mask = 1;
+		thi->t_state = Running;
+		spin_unlock_irqrestore(&thi->t_lock, flags);
+		flush_signals(current); /* otherw. may get -ERESTARTNOINTR */
+
+		nt = kthread_create(drbd_thread_setup, (void *) thi,
+				    "drbd%d_%s", mdev_to_minor(mdev), me);
+
+		if (IS_ERR(nt)) {
+			dev_err(DEV, "Couldn't start thread\n");
+
+			module_put(THIS_MODULE);
+			return FALSE;
+		}
+		spin_lock_irqsave(&thi->t_lock, flags);
+		thi->task = nt;
+		thi->t_state = Running;
+		spin_unlock_irqrestore(&thi->t_lock, flags);
+		wake_up_process(nt);
+		break;
+	case Exiting:
+		thi->t_state = Restarting;
+		dev_info(DEV, "Restarting %s thread (from %s [%d])\n",
+				me, current->comm, current->pid);
+		/* fall through */
+	case Running:
+	case Restarting:
+	default:
+		spin_unlock_irqrestore(&thi->t_lock, flags);
+		break;
+	}
+
+	return TRUE;
+}
+
+
+void _drbd_thread_stop(struct drbd_thread *thi, int restart, int wait)
+{
+	unsigned long flags;
+
+	enum drbd_thread_state ns = restart ? Restarting : Exiting;
+
+	/* may be called from state engine, holding the req lock irqsave */
+	spin_lock_irqsave(&thi->t_lock, flags);
+
+	if (thi->t_state == None) {
+		spin_unlock_irqrestore(&thi->t_lock, flags);
+		if (restart)
+			drbd_thread_start(thi);
+		return;
+	}
+
+	if (thi->t_state != ns) {
+		if (thi->task == NULL) {
+			spin_unlock_irqrestore(&thi->t_lock, flags);
+			return;
+		}
+
+		thi->t_state = ns;
+		smp_mb();
+		init_completion(&thi->stop);
+		if (thi->task != current)
+			force_sig(DRBD_SIGKILL, thi->task);
+
+	}
+
+	spin_unlock_irqrestore(&thi->t_lock, flags);
+
+	if (wait)
+		wait_for_completion(&thi->stop);
+}
+
+#ifdef CONFIG_SMP
+/**
+ * drbd_calc_cpu_mask() - Generate CPU masks, spread over all CPUs
+ * @mdev:	DRBD device.
+ *
+ * Forces all threads of a device onto the same CPU. This is beneficial for
+ * DRBD's performance. May be overwritten by user's configuration.
+ */
+void drbd_calc_cpu_mask(struct drbd_conf *mdev)
+{
+	int ord, cpu;
+
+	/* user override. */
+	if (cpumask_weight(mdev->cpu_mask))
+		return;
+
+	ord = mdev_to_minor(mdev) % cpumask_weight(cpu_online_mask);
+	for_each_online_cpu(cpu) {
+		if (ord-- == 0) {
+			cpumask_set_cpu(cpu, mdev->cpu_mask);
+			return;
+		}
+	}
+	/* should not be reached */
+	cpumask_setall(mdev->cpu_mask);
+}
+
+/**
+ * drbd_thread_current_set_cpu() - modifies the cpu mask of the _current_ thread
+ * @mdev:	DRBD device.
+ *
+ * call in the "main loop" of _all_ threads, no need for any mutex, current won't die
+ * prematurely.
+ */
+void drbd_thread_current_set_cpu(struct drbd_conf *mdev)
+{
+	struct task_struct *p = current;
+	struct drbd_thread *thi =
+		p == mdev->asender.task  ? &mdev->asender  :
+		p == mdev->receiver.task ? &mdev->receiver :
+		p == mdev->worker.task   ? &mdev->worker   :
+		NULL;
+	ERR_IF(thi == NULL)
+		return;
+	if (!thi->reset_cpu_mask)
+		return;
+	thi->reset_cpu_mask = 0;
+	set_cpus_allowed_ptr(p, mdev->cpu_mask);
+}
+#endif
+
+/* the appropriate socket mutex must be held already */
+int _drbd_send_cmd(struct drbd_conf *mdev, struct socket *sock,
+			  enum drbd_packets cmd, struct p_header *h,
+			  size_t size, unsigned msg_flags)
+{
+	int sent, ok;
+
+	ERR_IF(!h) return FALSE;
+	ERR_IF(!size) return FALSE;
+
+	h->magic   = BE_DRBD_MAGIC;
+	h->command = cpu_to_be16(cmd);
+	h->length  = cpu_to_be16(size-sizeof(struct p_header));
+
+	trace_drbd_packet(mdev, sock, 0, (void *)h, __FILE__, __LINE__);
+	sent = drbd_send(mdev, sock, h, size, msg_flags);
+
+	ok = (sent == size);
+	if (!ok)
+		dev_err(DEV, "short sent %s size=%d sent=%d\n",
+		    cmdname(cmd), (int)size, sent);
+	return ok;
+}
+
+/* don't pass the socket. we may only look at it
+ * when we hold the appropriate socket mutex.
+ */
+int drbd_send_cmd(struct drbd_conf *mdev, int use_data_socket,
+		  enum drbd_packets cmd, struct p_header *h, size_t size)
+{
+	int ok = 0;
+	struct socket *sock;
+
+	if (use_data_socket) {
+		mutex_lock(&mdev->data.mutex);
+		sock = mdev->data.socket;
+	} else {
+		mutex_lock(&mdev->meta.mutex);
+		sock = mdev->meta.socket;
+	}
+
+	/* drbd_disconnect() could have called drbd_free_sock()
+	 * while we were waiting in down()... */
+	if (likely(sock != NULL))
+		ok = _drbd_send_cmd(mdev, sock, cmd, h, size, 0);
+
+	if (use_data_socket)
+		mutex_unlock(&mdev->data.mutex);
+	else
+		mutex_unlock(&mdev->meta.mutex);
+	return ok;
+}
+
+int drbd_send_cmd2(struct drbd_conf *mdev, enum drbd_packets cmd, char *data,
+		   size_t size)
+{
+	struct p_header h;
+	int ok;
+
+	h.magic   = BE_DRBD_MAGIC;
+	h.command = cpu_to_be16(cmd);
+	h.length  = cpu_to_be16(size);
+
+	if (!drbd_get_data_sock(mdev))
+		return 0;
+
+	trace_drbd_packet(mdev, mdev->data.socket, 0, (void *)&h, __FILE__, __LINE__);
+
+	ok = (sizeof(h) ==
+		drbd_send(mdev, mdev->data.socket, &h, sizeof(h), 0));
+	ok = ok && (size ==
+		drbd_send(mdev, mdev->data.socket, data, size, 0));
+
+	drbd_put_data_sock(mdev);
+
+	return ok;
+}
+
+int drbd_send_sync_param(struct drbd_conf *mdev, struct syncer_conf *sc)
+{
+	struct p_rs_param_89 *p;
+	struct socket *sock;
+	int size, rv;
+	const int apv = mdev->agreed_pro_version;
+
+	size = apv <= 87 ? sizeof(struct p_rs_param)
+		: apv == 88 ? sizeof(struct p_rs_param)
+			+ strlen(mdev->sync_conf.verify_alg) + 1
+		: /* 89 */    sizeof(struct p_rs_param_89);
+
+	/* used from admin command context and receiver/worker context.
+	 * to avoid kmalloc, grab the socket right here,
+	 * then use the pre-allocated sbuf there */
+	mutex_lock(&mdev->data.mutex);
+	sock = mdev->data.socket;
+
+	if (likely(sock != NULL)) {
+		enum drbd_packets cmd = apv >= 89 ? P_SYNC_PARAM89 : P_SYNC_PARAM;
+
+		p = &mdev->data.sbuf.rs_param_89;
+
+		/* initialize verify_alg and csums_alg */
+		memset(p->verify_alg, 0, 2 * SHARED_SECRET_MAX);
+
+		p->rate = cpu_to_be32(sc->rate);
+
+		if (apv >= 88)
+			strcpy(p->verify_alg, mdev->sync_conf.verify_alg);
+		if (apv >= 89)
+			strcpy(p->csums_alg, mdev->sync_conf.csums_alg);
+
+		rv = _drbd_send_cmd(mdev, sock, cmd, &p->head, size, 0);
+	} else
+		rv = 0; /* not ok */
+
+	mutex_unlock(&mdev->data.mutex);
+
+	return rv;
+}
+
+int drbd_send_protocol(struct drbd_conf *mdev)
+{
+	struct p_protocol *p;
+	int size, rv;
+
+	size = sizeof(struct p_protocol);
+
+	if (mdev->agreed_pro_version >= 87)
+		size += strlen(mdev->net_conf->integrity_alg) + 1;
+
+	/* we must not recurse into our own queue,
+	 * as that is blocked during handshake */
+	p = kmalloc(size, GFP_NOIO);
+	if (p == NULL)
+		return 0;
+
+	p->protocol      = cpu_to_be32(mdev->net_conf->wire_protocol);
+	p->after_sb_0p   = cpu_to_be32(mdev->net_conf->after_sb_0p);
+	p->after_sb_1p   = cpu_to_be32(mdev->net_conf->after_sb_1p);
+	p->after_sb_2p   = cpu_to_be32(mdev->net_conf->after_sb_2p);
+	p->want_lose     = cpu_to_be32(mdev->net_conf->want_lose);
+	p->two_primaries = cpu_to_be32(mdev->net_conf->two_primaries);
+
+	if (mdev->agreed_pro_version >= 87)
+		strcpy(p->integrity_alg, mdev->net_conf->integrity_alg);
+
+	rv = drbd_send_cmd(mdev, USE_DATA_SOCKET, P_PROTOCOL,
+			   (struct p_header *)p, size);
+	kfree(p);
+	return rv;
+}
+
+int _drbd_send_uuids(struct drbd_conf *mdev, u64 uuid_flags)
+{
+	struct p_uuids p;
+	int i;
+
+	if (!get_ldev_if_state(mdev, D_NEGOTIATING))
+		return 1;
+
+	for (i = UI_CURRENT; i < UI_SIZE; i++)
+		p.uuid[i] = mdev->ldev ? cpu_to_be64(mdev->ldev->md.uuid[i]) : 0;
+
+	mdev->comm_bm_set = drbd_bm_total_weight(mdev);
+	p.uuid[UI_SIZE] = cpu_to_be64(mdev->comm_bm_set);
+	uuid_flags |= mdev->net_conf->want_lose ? 1 : 0;
+	uuid_flags |= test_bit(CRASHED_PRIMARY, &mdev->flags) ? 2 : 0;
+	uuid_flags |= mdev->new_state_tmp.disk == D_INCONSISTENT ? 4 : 0;
+	p.uuid[UI_FLAGS] = cpu_to_be64(uuid_flags);
+
+	put_ldev(mdev);
+
+	return drbd_send_cmd(mdev, USE_DATA_SOCKET, P_UUIDS,
+			     (struct p_header *)&p, sizeof(p));
+}
+
+int drbd_send_uuids(struct drbd_conf *mdev)
+{
+	return _drbd_send_uuids(mdev, 0);
+}
+
+int drbd_send_uuids_skip_initial_sync(struct drbd_conf *mdev)
+{
+	return _drbd_send_uuids(mdev, 8);
+}
+
+
+int drbd_send_sync_uuid(struct drbd_conf *mdev, u64 val)
+{
+	struct p_rs_uuid p;
+
+	p.uuid = cpu_to_be64(val);
+
+	return drbd_send_cmd(mdev, USE_DATA_SOCKET, P_SYNC_UUID,
+			     (struct p_header *)&p, sizeof(p));
+}
+
+int drbd_send_sizes(struct drbd_conf *mdev, int trigger_reply)
+{
+	struct p_sizes p;
+	sector_t d_size, u_size;
+	int q_order_type;
+	int ok;
+
+	if (get_ldev_if_state(mdev, D_NEGOTIATING)) {
+		D_ASSERT(mdev->ldev->backing_bdev);
+		d_size = drbd_get_max_capacity(mdev->ldev);
+		u_size = mdev->ldev->dc.disk_size;
+		q_order_type = drbd_queue_order_type(mdev);
+		p.queue_order_type = cpu_to_be32(drbd_queue_order_type(mdev));
+		put_ldev(mdev);
+	} else {
+		d_size = 0;
+		u_size = 0;
+		q_order_type = QUEUE_ORDERED_NONE;
+	}
+
+	p.d_size = cpu_to_be64(d_size);
+	p.u_size = cpu_to_be64(u_size);
+	p.c_size = cpu_to_be64(trigger_reply ? 0 : drbd_get_capacity(mdev->this_bdev));
+	p.max_segment_size = cpu_to_be32(queue_max_segment_size(mdev->rq_queue));
+	p.queue_order_type = cpu_to_be32(q_order_type);
+
+	ok = drbd_send_cmd(mdev, USE_DATA_SOCKET, P_SIZES,
+			   (struct p_header *)&p, sizeof(p));
+	return ok;
+}
+
+/**
+ * drbd_send_state() - Sends the drbd state to the peer
+ * @mdev:	DRBD device.
+ */
+int drbd_send_state(struct drbd_conf *mdev)
+{
+	struct socket *sock;
+	struct p_state p;
+	int ok = 0;
+
+	/* Grab state lock so we wont send state if we're in the middle
+	 * of a cluster wide state change on another thread */
+	drbd_state_lock(mdev);
+
+	mutex_lock(&mdev->data.mutex);
+
+	p.state = cpu_to_be32(mdev->state.i); /* Within the send mutex */
+	sock = mdev->data.socket;
+
+	if (likely(sock != NULL)) {
+		ok = _drbd_send_cmd(mdev, sock, P_STATE,
+				    (struct p_header *)&p, sizeof(p), 0);
+	}
+
+	mutex_unlock(&mdev->data.mutex);
+
+	drbd_state_unlock(mdev);
+	return ok;
+}
+
+int drbd_send_state_req(struct drbd_conf *mdev,
+	union drbd_state mask, union drbd_state val)
+{
+	struct p_req_state p;
+
+	p.mask    = cpu_to_be32(mask.i);
+	p.val     = cpu_to_be32(val.i);
+
+	return drbd_send_cmd(mdev, USE_DATA_SOCKET, P_STATE_CHG_REQ,
+			     (struct p_header *)&p, sizeof(p));
+}
+
+int drbd_send_sr_reply(struct drbd_conf *mdev, int retcode)
+{
+	struct p_req_state_reply p;
+
+	p.retcode    = cpu_to_be32(retcode);
+
+	return drbd_send_cmd(mdev, USE_META_SOCKET, P_STATE_CHG_REPLY,
+			     (struct p_header *)&p, sizeof(p));
+}
+
+int fill_bitmap_rle_bits(struct drbd_conf *mdev,
+	struct p_compressed_bm *p,
+	struct bm_xfer_ctx *c)
+{
+	struct bitstream bs;
+	unsigned long plain_bits;
+	unsigned long tmp;
+	unsigned long rl;
+	unsigned len;
+	unsigned toggle;
+	int bits;
+
+	/* may we use this feature? */
+	if ((mdev->sync_conf.use_rle == 0) ||
+		(mdev->agreed_pro_version < 90))
+			return 0;
+
+	if (c->bit_offset >= c->bm_bits)
+		return 0; /* nothing to do. */
+
+	/* use at most thus many bytes */
+	bitstream_init(&bs, p->code, BM_PACKET_VLI_BYTES_MAX, 0);
+	memset(p->code, 0, BM_PACKET_VLI_BYTES_MAX);
+	/* plain bits covered in this code string */
+	plain_bits = 0;
+
+	/* p->encoding & 0x80 stores whether the first run length is set.
+	 * bit offset is implicit.
+	 * start with toggle == 2 to be able to tell the first iteration */
+	toggle = 2;
+
+	/* see how much plain bits we can stuff into one packet
+	 * using RLE and VLI. */
+	do {
+		tmp = (toggle == 0) ? _drbd_bm_find_next_zero(mdev, c->bit_offset)
+				    : _drbd_bm_find_next(mdev, c->bit_offset);
+		if (tmp == -1UL)
+			tmp = c->bm_bits;
+		rl = tmp - c->bit_offset;
+
+		if (toggle == 2) { /* first iteration */
+			if (rl == 0) {
+				/* the first checked bit was set,
+				 * store start value, */
+				DCBP_set_start(p, 1);
+				/* but skip encoding of zero run length */
+				toggle = !toggle;
+				continue;
+			}
+			DCBP_set_start(p, 0);
+		}
+
+		/* paranoia: catch zero runlength.
+		 * can only happen if bitmap is modified while we scan it. */
+		if (rl == 0) {
+			dev_err(DEV, "unexpected zero runlength while encoding bitmap "
+			    "t:%u bo:%lu\n", toggle, c->bit_offset);
+			return -1;
+		}
+
+		bits = vli_encode_bits(&bs, rl);
+		if (bits == -ENOBUFS) /* buffer full */
+			break;
+		if (bits <= 0) {
+			dev_err(DEV, "error while encoding bitmap: %d\n", bits);
+			return 0;
+		}
+
+		toggle = !toggle;
+		plain_bits += rl;
+		c->bit_offset = tmp;
+	} while (c->bit_offset < c->bm_bits);
+
+	len = bs.cur.b - p->code + !!bs.cur.bit;
+
+	if (plain_bits < (len << 3)) {
+		/* incompressible with this method.
+		 * we need to rewind both word and bit position. */
+		c->bit_offset -= plain_bits;
+		bm_xfer_ctx_bit_to_word_offset(c);
+		c->bit_offset = c->word_offset * BITS_PER_LONG;
+		return 0;
+	}
+
+	/* RLE + VLI was able to compress it just fine.
+	 * update c->word_offset. */
+	bm_xfer_ctx_bit_to_word_offset(c);
+
+	/* store pad_bits */
+	DCBP_set_pad_bits(p, (8 - bs.cur.bit) & 0x7);
+
+	return len;
+}
+
+enum { OK, FAILED, DONE }
+send_bitmap_rle_or_plain(struct drbd_conf *mdev,
+	struct p_header *h, struct bm_xfer_ctx *c)
+{
+	struct p_compressed_bm *p = (void*)h;
+	unsigned long num_words;
+	int len;
+	int ok;
+
+	len = fill_bitmap_rle_bits(mdev, p, c);
+
+	if (len < 0)
+		return FAILED;
+
+	if (len) {
+		DCBP_set_code(p, RLE_VLI_Bits);
+		ok = _drbd_send_cmd(mdev, mdev->data.socket, P_COMPRESSED_BITMAP, h,
+			sizeof(*p) + len, 0);
+
+		c->packets[0]++;
+		c->bytes[0] += sizeof(*p) + len;
+
+		if (c->bit_offset >= c->bm_bits)
+			len = 0; /* DONE */
+	} else {
+		/* was not compressible.
+		 * send a buffer full of plain text bits instead. */
+		num_words = min_t(size_t, BM_PACKET_WORDS, c->bm_words - c->word_offset);
+		len = num_words * sizeof(long);
+		if (len)
+			drbd_bm_get_lel(mdev, c->word_offset, num_words, (unsigned long*)h->payload);
+		ok = _drbd_send_cmd(mdev, mdev->data.socket, P_BITMAP,
+				   h, sizeof(struct p_header) + len, 0);
+		c->word_offset += num_words;
+		c->bit_offset = c->word_offset * BITS_PER_LONG;
+
+		c->packets[1]++;
+		c->bytes[1] += sizeof(struct p_header) + len;
+
+		if (c->bit_offset > c->bm_bits)
+			c->bit_offset = c->bm_bits;
+	}
+	ok = ok ? ((len == 0) ? DONE : OK) : FAILED;
+
+	if (ok == DONE)
+		INFO_bm_xfer_stats(mdev, "send", c);
+	return ok;
+}
+
+/* See the comment at receive_bitmap() */
+int _drbd_send_bitmap(struct drbd_conf *mdev)
+{
+	struct bm_xfer_ctx c;
+	struct p_header *p;
+	int ret;
+
+	ERR_IF(!mdev->bitmap) return FALSE;
+
+	/* maybe we should use some per thread scratch page,
+	 * and allocate that during initial device creation? */
+	p = (struct p_header *) __get_free_page(GFP_NOIO);
+	if (!p) {
+		dev_err(DEV, "failed to allocate one page buffer in %s\n", __func__);
+		return FALSE;
+	}
+
+	if (get_ldev(mdev)) {
+		if (drbd_md_test_flag(mdev->ldev, MDF_FULL_SYNC)) {
+			dev_info(DEV, "Writing the whole bitmap, MDF_FullSync was set.\n");
+			drbd_bm_set_all(mdev);
+			if (drbd_bm_write(mdev)) {
+				/* write_bm did fail! Leave full sync flag set in Meta P_DATA
+				 * but otherwise process as per normal - need to tell other
+				 * side that a full resync is required! */
+				dev_err(DEV, "Failed to write bitmap to disk!\n");
+			} else {
+				drbd_md_clear_flag(mdev, MDF_FULL_SYNC);
+				drbd_md_sync(mdev);
+			}
+		}
+		put_ldev(mdev);
+	}
+
+	c = (struct bm_xfer_ctx) {
+		.bm_bits = drbd_bm_bits(mdev),
+		.bm_words = drbd_bm_words(mdev),
+	};
+
+	do {
+		ret = send_bitmap_rle_or_plain(mdev, p, &c);
+	} while (ret == OK);
+
+	free_page((unsigned long) p);
+	return (ret == DONE);
+}
+
+int drbd_send_bitmap(struct drbd_conf *mdev)
+{
+	int err;
+
+	if (!drbd_get_data_sock(mdev))
+		return -1;
+	err = !_drbd_send_bitmap(mdev);
+	drbd_put_data_sock(mdev);
+	return err;
+}
+
+int drbd_send_b_ack(struct drbd_conf *mdev, u32 barrier_nr, u32 set_size)
+{
+	int ok;
+	struct p_barrier_ack p;
+
+	p.barrier  = barrier_nr;
+	p.set_size = cpu_to_be32(set_size);
+
+	if (mdev->state.conn < C_CONNECTED)
+		return FALSE;
+	ok = drbd_send_cmd(mdev, USE_META_SOCKET, P_BARRIER_ACK,
+			(struct p_header *)&p, sizeof(p));
+	return ok;
+}
+
+/**
+ * _drbd_send_ack() - Sends an ack packet
+ * @mdev:	DRBD device.
+ * @cmd:	Packet command code.
+ * @sector:	sector, needs to be in big endian byte order
+ * @blksize:	size in byte, needs to be in big endian byte order
+ * @block_id:	Id, big endian byte order
+ */
+static int _drbd_send_ack(struct drbd_conf *mdev, enum drbd_packets cmd,
+			  u64 sector,
+			  u32 blksize,
+			  u64 block_id)
+{
+	int ok;
+	struct p_block_ack p;
+
+	p.sector   = sector;
+	p.block_id = block_id;
+	p.blksize  = blksize;
+	p.seq_num  = cpu_to_be32(atomic_add_return(1, &mdev->packet_seq));
+
+	if (!mdev->meta.socket || mdev->state.conn < C_CONNECTED)
+		return FALSE;
+	ok = drbd_send_cmd(mdev, USE_META_SOCKET, cmd,
+				(struct p_header *)&p, sizeof(p));
+	return ok;
+}
+
+int drbd_send_ack_dp(struct drbd_conf *mdev, enum drbd_packets cmd,
+		     struct p_data *dp)
+{
+	const int header_size = sizeof(struct p_data)
+			      - sizeof(struct p_header);
+	int data_size  = ((struct p_header *)dp)->length - header_size;
+
+	return _drbd_send_ack(mdev, cmd, dp->sector, cpu_to_be32(data_size),
+			      dp->block_id);
+}
+
+int drbd_send_ack_rp(struct drbd_conf *mdev, enum drbd_packets cmd,
+		     struct p_block_req *rp)
+{
+	return _drbd_send_ack(mdev, cmd, rp->sector, rp->blksize, rp->block_id);
+}
+
+/**
+ * drbd_send_ack() - Sends an ack packet
+ * @mdev:	DRBD device.
+ * @cmd:	Packet command code.
+ * @e:		Epoch entry.
+ */
+int drbd_send_ack(struct drbd_conf *mdev,
+	enum drbd_packets cmd, struct drbd_epoch_entry *e)
+{
+	return _drbd_send_ack(mdev, cmd,
+			      cpu_to_be64(e->sector),
+			      cpu_to_be32(e->size),
+			      e->block_id);
+}
+
+/* This function misuses the block_id field to signal if the blocks
+ * are is sync or not. */
+int drbd_send_ack_ex(struct drbd_conf *mdev, enum drbd_packets cmd,
+		     sector_t sector, int blksize, u64 block_id)
+{
+	return _drbd_send_ack(mdev, cmd,
+			      cpu_to_be64(sector),
+			      cpu_to_be32(blksize),
+			      cpu_to_be64(block_id));
+}
+
+int drbd_send_drequest(struct drbd_conf *mdev, int cmd,
+		       sector_t sector, int size, u64 block_id)
+{
+	int ok;
+	struct p_block_req p;
+
+	p.sector   = cpu_to_be64(sector);
+	p.block_id = block_id;
+	p.blksize  = cpu_to_be32(size);
+
+	ok = drbd_send_cmd(mdev, USE_DATA_SOCKET, cmd,
+				(struct p_header *)&p, sizeof(p));
+	return ok;
+}
+
+int drbd_send_drequest_csum(struct drbd_conf *mdev,
+			    sector_t sector, int size,
+			    void *digest, int digest_size,
+			    enum drbd_packets cmd)
+{
+	int ok;
+	struct p_block_req p;
+
+	p.sector   = cpu_to_be64(sector);
+	p.block_id = BE_DRBD_MAGIC + 0xbeef;
+	p.blksize  = cpu_to_be32(size);
+
+	p.head.magic   = BE_DRBD_MAGIC;
+	p.head.command = cpu_to_be16(cmd);
+	p.head.length  = cpu_to_be16(sizeof(p) - sizeof(struct p_header) + digest_size);
+
+	mutex_lock(&mdev->data.mutex);
+
+	ok = (sizeof(p) == drbd_send(mdev, mdev->data.socket, &p, sizeof(p), 0));
+	ok = ok && (digest_size == drbd_send(mdev, mdev->data.socket, digest, digest_size, 0));
+
+	mutex_unlock(&mdev->data.mutex);
+
+	return ok;
+}
+
+int drbd_send_ov_request(struct drbd_conf *mdev, sector_t sector, int size)
+{
+	int ok;
+	struct p_block_req p;
+
+	p.sector   = cpu_to_be64(sector);
+	p.block_id = BE_DRBD_MAGIC + 0xbabe;
+	p.blksize  = cpu_to_be32(size);
+
+	ok = drbd_send_cmd(mdev, USE_DATA_SOCKET, P_OV_REQUEST,
+			   (struct p_header *)&p, sizeof(p));
+	return ok;
+}
+
+/* called on sndtimeo
+ * returns FALSE if we should retry,
+ * TRUE if we think connection is dead
+ */
+static int we_should_drop_the_connection(struct drbd_conf *mdev, struct socket *sock)
+{
+	int drop_it;
+	/* long elapsed = (long)(jiffies - mdev->last_received); */
+
+	drop_it =   mdev->meta.socket == sock
+		|| !mdev->asender.task
+		|| get_t_state(&mdev->asender) != Running
+		|| mdev->state.conn < C_CONNECTED;
+
+	if (drop_it)
+		return TRUE;
+
+	drop_it = !--mdev->ko_count;
+	if (!drop_it) {
+		dev_err(DEV, "[%s/%d] sock_sendmsg time expired, ko = %u\n",
+		       current->comm, current->pid, mdev->ko_count);
+		request_ping(mdev);
+	}
+
+	return drop_it; /* && (mdev->state == R_PRIMARY) */;
+}
+
+/* The idea of sendpage seems to be to put some kind of reference
+ * to the page into the skb, and to hand it over to the NIC. In
+ * this process get_page() gets called.
+ *
+ * As soon as the page was really sent over the network put_page()
+ * gets called by some part of the network layer. [ NIC driver? ]
+ *
+ * [ get_page() / put_page() increment/decrement the count. If count
+ *   reaches 0 the page will be freed. ]
+ *
+ * This works nicely with pages from FSs.
+ * But this means that in protocol A we might signal IO completion too early!
+ *
+ * In order not to corrupt data during a resync we must make sure
+ * that we do not reuse our own buffer pages (EEs) to early, therefore
+ * we have the net_ee list.
+ *
+ * XFS seems to have problems, still, it submits pages with page_count == 0!
+ * As a workaround, we disable sendpage on pages
+ * with page_count == 0 or PageSlab.
+ */
+static int _drbd_no_send_page(struct drbd_conf *mdev, struct page *page,
+		   int offset, size_t size)
+{
+	int sent = drbd_send(mdev, mdev->data.socket, kmap(page) + offset, size, 0);
+	kunmap(page);
+	if (sent == size)
+		mdev->send_cnt += size>>9;
+	return sent == size;
+}
+
+static int _drbd_send_page(struct drbd_conf *mdev, struct page *page,
+		    int offset, size_t size)
+{
+	mm_segment_t oldfs = get_fs();
+	int sent, ok;
+	int len = size;
+
+	/* e.g. XFS meta- & log-data is in slab pages, which have a
+	 * page_count of 0 and/or have PageSlab() set.
+	 * we cannot use send_page for those, as that does get_page();
+	 * put_page(); and would cause either a VM_BUG directly, or
+	 * __page_cache_release a page that would actually still be referenced
+	 * by someone, leading to some obscure delayed Oops somewhere else. */
+	if (disable_sendpage || (page_count(page) < 1) || PageSlab(page))
+		return _drbd_no_send_page(mdev, page, offset, size);
+
+	drbd_update_congested(mdev);
+	set_fs(KERNEL_DS);
+	do {
+		sent = mdev->data.socket->ops->sendpage(mdev->data.socket, page,
+							offset, len,
+							MSG_NOSIGNAL);
+		if (sent == -EAGAIN) {
+			if (we_should_drop_the_connection(mdev,
+							  mdev->data.socket))
+				break;
+			else
+				continue;
+		}
+		if (sent <= 0) {
+			dev_warn(DEV, "%s: size=%d len=%d sent=%d\n",
+			     __func__, (int)size, len, sent);
+			break;
+		}
+		len    -= sent;
+		offset += sent;
+	} while (len > 0 /* THINK && mdev->cstate >= C_CONNECTED*/);
+	set_fs(oldfs);
+	clear_bit(NET_CONGESTED, &mdev->flags);
+
+	ok = (len == 0);
+	if (likely(ok))
+		mdev->send_cnt += size>>9;
+	return ok;
+}
+
+static int _drbd_send_bio(struct drbd_conf *mdev, struct bio *bio)
+{
+	struct bio_vec *bvec;
+	int i;
+	__bio_for_each_segment(bvec, bio, i, 0) {
+		if (!_drbd_no_send_page(mdev, bvec->bv_page,
+				     bvec->bv_offset, bvec->bv_len))
+			return 0;
+	}
+	return 1;
+}
+
+static int _drbd_send_zc_bio(struct drbd_conf *mdev, struct bio *bio)
+{
+	struct bio_vec *bvec;
+	int i;
+	__bio_for_each_segment(bvec, bio, i, 0) {
+		if (!_drbd_send_page(mdev, bvec->bv_page,
+				     bvec->bv_offset, bvec->bv_len))
+			return 0;
+	}
+
+	return 1;
+}
+
+/* Used to send write requests
+ * R_PRIMARY -> Peer	(P_DATA)
+ */
+int drbd_send_dblock(struct drbd_conf *mdev, struct drbd_request *req)
+{
+	int ok = 1;
+	struct p_data p;
+	unsigned int dp_flags = 0;
+	void *dgb;
+	int dgs;
+
+	if (!drbd_get_data_sock(mdev))
+		return 0;
+
+	dgs = (mdev->agreed_pro_version >= 87 && mdev->integrity_w_tfm) ?
+		crypto_hash_digestsize(mdev->integrity_w_tfm) : 0;
+
+	p.head.magic   = BE_DRBD_MAGIC;
+	p.head.command = cpu_to_be16(P_DATA);
+	p.head.length  =
+		cpu_to_be16(sizeof(p) - sizeof(struct p_header) + dgs + req->size);
+
+	p.sector   = cpu_to_be64(req->sector);
+	p.block_id = (unsigned long)req;
+	p.seq_num  = cpu_to_be32(req->seq_num =
+				 atomic_add_return(1, &mdev->packet_seq));
+	dp_flags = 0;
+
+	/* NOTE: no need to check if barriers supported here as we would
+	 *       not pass the test in make_request_common in that case
+	 */
+	if (bio_rw_flagged(req->master_bio, BIO_RW_BARRIER)) {
+		dev_err(DEV, "ASSERT FAILED would have set DP_HARDBARRIER\n");
+		/* dp_flags |= DP_HARDBARRIER; */
+	}
+	if (bio_rw_flagged(req->master_bio, BIO_RW_SYNCIO))
+		dp_flags |= DP_RW_SYNC;
+	/* for now handle SYNCIO and UNPLUG
+	 * as if they still were one and the same flag */
+	if (bio_rw_flagged(req->master_bio, BIO_RW_UNPLUG))
+		dp_flags |= DP_RW_SYNC;
+	if (mdev->state.conn >= C_SYNC_SOURCE &&
+	    mdev->state.conn <= C_PAUSED_SYNC_T)
+		dp_flags |= DP_MAY_SET_IN_SYNC;
+
+	p.dp_flags = cpu_to_be32(dp_flags);
+	trace_drbd_packet(mdev, mdev->data.socket, 0, (void *)&p, __FILE__, __LINE__);
+	set_bit(UNPLUG_REMOTE, &mdev->flags);
+	ok = (sizeof(p) ==
+		drbd_send(mdev, mdev->data.socket, &p, sizeof(p), MSG_MORE));
+	if (ok && dgs) {
+		dgb = mdev->int_dig_out;
+		drbd_csum(mdev, mdev->integrity_w_tfm, req->master_bio, dgb);
+		ok = drbd_send(mdev, mdev->data.socket, dgb, dgs, MSG_MORE);
+	}
+	if (ok) {
+		if (mdev->net_conf->wire_protocol == DRBD_PROT_A)
+			ok = _drbd_send_bio(mdev, req->master_bio);
+		else
+			ok = _drbd_send_zc_bio(mdev, req->master_bio);
+	}
+
+	drbd_put_data_sock(mdev);
+	return ok;
+}
+
+/* answer packet, used to send data back for read requests:
+ *  Peer       -> (diskless) R_PRIMARY   (P_DATA_REPLY)
+ *  C_SYNC_SOURCE -> C_SYNC_TARGET         (P_RS_DATA_REPLY)
+ */
+int drbd_send_block(struct drbd_conf *mdev, enum drbd_packets cmd,
+		    struct drbd_epoch_entry *e)
+{
+	int ok;
+	struct p_data p;
+	void *dgb;
+	int dgs;
+
+	dgs = (mdev->agreed_pro_version >= 87 && mdev->integrity_w_tfm) ?
+		crypto_hash_digestsize(mdev->integrity_w_tfm) : 0;
+
+	p.head.magic   = BE_DRBD_MAGIC;
+	p.head.command = cpu_to_be16(cmd);
+	p.head.length  =
+		cpu_to_be16(sizeof(p) - sizeof(struct p_header) + dgs + e->size);
+
+	p.sector   = cpu_to_be64(e->sector);
+	p.block_id = e->block_id;
+	/* p.seq_num  = 0;    No sequence numbers here.. */
+
+	/* Only called by our kernel thread.
+	 * This one may be interrupted by DRBD_SIG and/or DRBD_SIGKILL
+	 * in response to admin command or module unload.
+	 */
+	if (!drbd_get_data_sock(mdev))
+		return 0;
+
+	trace_drbd_packet(mdev, mdev->data.socket, 0, (void *)&p, __FILE__, __LINE__);
+	ok = sizeof(p) == drbd_send(mdev, mdev->data.socket, &p,
+					sizeof(p), MSG_MORE);
+	if (ok && dgs) {
+		dgb = mdev->int_dig_out;
+		drbd_csum(mdev, mdev->integrity_w_tfm, e->private_bio, dgb);
+		ok = drbd_send(mdev, mdev->data.socket, dgb, dgs, MSG_MORE);
+	}
+	if (ok)
+		ok = _drbd_send_zc_bio(mdev, e->private_bio);
+
+	drbd_put_data_sock(mdev);
+	return ok;
+}
+
+/*
+  drbd_send distinguishes two cases:
+
+  Packets sent via the data socket "sock"
+  and packets sent via the meta data socket "msock"
+
+		    sock                      msock
+  -----------------+-------------------------+------------------------------
+  timeout           conf.timeout / 2          conf.timeout / 2
+  timeout action    send a ping via msock     Abort communication
+					      and close all sockets
+*/
+
+/*
+ * you must have down()ed the appropriate [m]sock_mutex elsewhere!
+ */
+int drbd_send(struct drbd_conf *mdev, struct socket *sock,
+	      void *buf, size_t size, unsigned msg_flags)
+{
+	struct kvec iov;
+	struct msghdr msg;
+	int rv, sent = 0;
+
+	if (!sock)
+		return -1000;
+
+	/* THINK  if (signal_pending) return ... ? */
+
+	iov.iov_base = buf;
+	iov.iov_len  = size;
+
+	msg.msg_name       = NULL;
+	msg.msg_namelen    = 0;
+	msg.msg_control    = NULL;
+	msg.msg_controllen = 0;
+	msg.msg_flags      = msg_flags | MSG_NOSIGNAL;
+
+	if (sock == mdev->data.socket) {
+		mdev->ko_count = mdev->net_conf->ko_count;
+		drbd_update_congested(mdev);
+	}
+	do {
+		/* STRANGE
+		 * tcp_sendmsg does _not_ use its size parameter at all ?
+		 *
+		 * -EAGAIN on timeout, -EINTR on signal.
+		 */
+/* THINK
+ * do we need to block DRBD_SIG if sock == &meta.socket ??
+ * otherwise wake_asender() might interrupt some send_*Ack !
+ */
+		rv = kernel_sendmsg(sock, &msg, &iov, 1, size);
+		if (rv == -EAGAIN) {
+			if (we_should_drop_the_connection(mdev, sock))
+				break;
+			else
+				continue;
+		}
+		D_ASSERT(rv != 0);
+		if (rv == -EINTR) {
+			flush_signals(current);
+			rv = 0;
+		}
+		if (rv < 0)
+			break;
+		sent += rv;
+		iov.iov_base += rv;
+		iov.iov_len  -= rv;
+	} while (sent < size);
+
+	if (sock == mdev->data.socket)
+		clear_bit(NET_CONGESTED, &mdev->flags);
+
+	if (rv <= 0) {
+		if (rv != -EAGAIN) {
+			dev_err(DEV, "%s_sendmsg returned %d\n",
+			    sock == mdev->meta.socket ? "msock" : "sock",
+			    rv);
+			drbd_force_state(mdev, NS(conn, C_BROKEN_PIPE));
+		} else
+			drbd_force_state(mdev, NS(conn, C_TIMEOUT));
+	}
+
+	return sent;
+}
+
+static int drbd_open(struct block_device *bdev, fmode_t mode)
+{
+	struct drbd_conf *mdev = bdev->bd_disk->private_data;
+	unsigned long flags;
+	int rv = 0;
+
+	spin_lock_irqsave(&mdev->req_lock, flags);
+	/* to have a stable mdev->state.role
+	 * and no race with updating open_cnt */
+
+	if (mdev->state.role != R_PRIMARY) {
+		if (mode & FMODE_WRITE)
+			rv = -EROFS;
+		else if (!allow_oos)
+			rv = -EMEDIUMTYPE;
+	}
+
+	if (!rv)
+		mdev->open_cnt++;
+	spin_unlock_irqrestore(&mdev->req_lock, flags);
+
+	return rv;
+}
+
+static int drbd_release(struct gendisk *gd, fmode_t mode)
+{
+	struct drbd_conf *mdev = gd->private_data;
+	mdev->open_cnt--;
+	return 0;
+}
+
+static void drbd_unplug_fn(struct request_queue *q)
+{
+	struct drbd_conf *mdev = q->queuedata;
+
+	trace_drbd_unplug(mdev, "got unplugged");
+
+	/* unplug FIRST */
+	spin_lock_irq(q->queue_lock);
+	blk_remove_plug(q);
+	spin_unlock_irq(q->queue_lock);
+
+	/* only if connected */
+	spin_lock_irq(&mdev->req_lock);
+	if (mdev->state.pdsk >= D_INCONSISTENT && mdev->state.conn >= C_CONNECTED) {
+		D_ASSERT(mdev->state.role == R_PRIMARY);
+		if (test_and_clear_bit(UNPLUG_REMOTE, &mdev->flags)) {
+			/* add to the data.work queue,
+			 * unless already queued.
+			 * XXX this might be a good addition to drbd_queue_work
+			 * anyways, to detect "double queuing" ... */
+			if (list_empty(&mdev->unplug_work.list))
+				drbd_queue_work(&mdev->data.work,
+						&mdev->unplug_work);
+		}
+	}
+	spin_unlock_irq(&mdev->req_lock);
+
+	if (mdev->state.disk >= D_INCONSISTENT)
+		drbd_kick_lo(mdev);
+}
+
+static void drbd_set_defaults(struct drbd_conf *mdev)
+{
+	mdev->sync_conf.after      = DRBD_AFTER_DEF;
+	mdev->sync_conf.rate       = DRBD_RATE_DEF;
+	mdev->sync_conf.al_extents = DRBD_AL_EXTENTS_DEF;
+	mdev->state = (union drbd_state) {
+		{ .role = R_SECONDARY,
+		  .peer = R_UNKNOWN,
+		  .conn = C_STANDALONE,
+		  .disk = D_DISKLESS,
+		  .pdsk = D_UNKNOWN,
+		  .susp = 0
+		} };
+}
+
+void drbd_init_set_defaults(struct drbd_conf *mdev)
+{
+	/* the memset(,0,) did most of this.
+	 * note: only assignments, no allocation in here */
+
+	drbd_set_defaults(mdev);
+
+	/* for now, we do NOT yet support it,
+	 * even though we start some framework
+	 * to eventually support barriers */
+	set_bit(NO_BARRIER_SUPP, &mdev->flags);
+
+	atomic_set(&mdev->ap_bio_cnt, 0);
+	atomic_set(&mdev->ap_pending_cnt, 0);
+	atomic_set(&mdev->rs_pending_cnt, 0);
+	atomic_set(&mdev->unacked_cnt, 0);
+	atomic_set(&mdev->local_cnt, 0);
+	atomic_set(&mdev->net_cnt, 0);
+	atomic_set(&mdev->packet_seq, 0);
+	atomic_set(&mdev->pp_in_use, 0);
+
+	mutex_init(&mdev->md_io_mutex);
+	mutex_init(&mdev->data.mutex);
+	mutex_init(&mdev->meta.mutex);
+	sema_init(&mdev->data.work.s, 0);
+	sema_init(&mdev->meta.work.s, 0);
+	mutex_init(&mdev->state_mutex);
+
+	spin_lock_init(&mdev->data.work.q_lock);
+	spin_lock_init(&mdev->meta.work.q_lock);
+
+	spin_lock_init(&mdev->al_lock);
+	spin_lock_init(&mdev->req_lock);
+	spin_lock_init(&mdev->peer_seq_lock);
+	spin_lock_init(&mdev->epoch_lock);
+
+	INIT_LIST_HEAD(&mdev->active_ee);
+	INIT_LIST_HEAD(&mdev->sync_ee);
+	INIT_LIST_HEAD(&mdev->done_ee);
+	INIT_LIST_HEAD(&mdev->read_ee);
+	INIT_LIST_HEAD(&mdev->net_ee);
+	INIT_LIST_HEAD(&mdev->resync_reads);
+	INIT_LIST_HEAD(&mdev->data.work.q);
+	INIT_LIST_HEAD(&mdev->meta.work.q);
+	INIT_LIST_HEAD(&mdev->resync_work.list);
+	INIT_LIST_HEAD(&mdev->unplug_work.list);
+	INIT_LIST_HEAD(&mdev->md_sync_work.list);
+	INIT_LIST_HEAD(&mdev->bm_io_work.w.list);
+	mdev->resync_work.cb  = w_resync_inactive;
+	mdev->unplug_work.cb  = w_send_write_hint;
+	mdev->md_sync_work.cb = w_md_sync;
+	mdev->bm_io_work.w.cb = w_bitmap_io;
+	init_timer(&mdev->resync_timer);
+	init_timer(&mdev->md_sync_timer);
+	mdev->resync_timer.function = resync_timer_fn;
+	mdev->resync_timer.data = (unsigned long) mdev;
+	mdev->md_sync_timer.function = md_sync_timer_fn;
+	mdev->md_sync_timer.data = (unsigned long) mdev;
+
+	init_waitqueue_head(&mdev->misc_wait);
+	init_waitqueue_head(&mdev->state_wait);
+	init_waitqueue_head(&mdev->ee_wait);
+	init_waitqueue_head(&mdev->al_wait);
+	init_waitqueue_head(&mdev->seq_wait);
+
+	drbd_thread_init(mdev, &mdev->receiver, drbdd_init);
+	drbd_thread_init(mdev, &mdev->worker, drbd_worker);
+	drbd_thread_init(mdev, &mdev->asender, drbd_asender);
+
+	mdev->agreed_pro_version = PRO_VERSION_MAX;
+	mdev->write_ordering = WO_bio_barrier;
+	mdev->resync_wenr = LC_FREE;
+}
+
+void drbd_mdev_cleanup(struct drbd_conf *mdev)
+{
+	if (mdev->receiver.t_state != None)
+		dev_err(DEV, "ASSERT FAILED: receiver t_state == %d expected 0.\n",
+				mdev->receiver.t_state);
+
+	/* no need to lock it, I'm the only thread alive */
+	if (atomic_read(&mdev->current_epoch->epoch_size) !=  0)
+		dev_err(DEV, "epoch_size:%d\n", atomic_read(&mdev->current_epoch->epoch_size));
+	mdev->al_writ_cnt  =
+	mdev->bm_writ_cnt  =
+	mdev->read_cnt     =
+	mdev->recv_cnt     =
+	mdev->send_cnt     =
+	mdev->writ_cnt     =
+	mdev->p_size       =
+	mdev->rs_start     =
+	mdev->rs_total     =
+	mdev->rs_failed    =
+	mdev->rs_mark_left =
+	mdev->rs_mark_time = 0;
+	D_ASSERT(mdev->net_conf == NULL);
+
+	drbd_set_my_capacity(mdev, 0);
+	if (mdev->bitmap) {
+		/* maybe never allocated. */
+		drbd_bm_resize(mdev, 0);
+		drbd_bm_cleanup(mdev);
+	}
+
+	drbd_free_resources(mdev);
+
+	/*
+	 * currently we drbd_init_ee only on module load, so
+	 * we may do drbd_release_ee only on module unload!
+	 */
+	D_ASSERT(list_empty(&mdev->active_ee));
+	D_ASSERT(list_empty(&mdev->sync_ee));
+	D_ASSERT(list_empty(&mdev->done_ee));
+	D_ASSERT(list_empty(&mdev->read_ee));
+	D_ASSERT(list_empty(&mdev->net_ee));
+	D_ASSERT(list_empty(&mdev->resync_reads));
+	D_ASSERT(list_empty(&mdev->data.work.q));
+	D_ASSERT(list_empty(&mdev->meta.work.q));
+	D_ASSERT(list_empty(&mdev->resync_work.list));
+	D_ASSERT(list_empty(&mdev->unplug_work.list));
+
+}
+
+
+static void drbd_destroy_mempools(void)
+{
+	struct page *page;
+
+	while (drbd_pp_pool) {
+		page = drbd_pp_pool;
+		drbd_pp_pool = (struct page *)page_private(page);
+		__free_page(page);
+		drbd_pp_vacant--;
+	}
+
+	/* D_ASSERT(atomic_read(&drbd_pp_vacant)==0); */
+
+	if (drbd_ee_mempool)
+		mempool_destroy(drbd_ee_mempool);
+	if (drbd_request_mempool)
+		mempool_destroy(drbd_request_mempool);
+	if (drbd_ee_cache)
+		kmem_cache_destroy(drbd_ee_cache);
+	if (drbd_request_cache)
+		kmem_cache_destroy(drbd_request_cache);
+	if (drbd_bm_ext_cache)
+		kmem_cache_destroy(drbd_bm_ext_cache);
+	if (drbd_al_ext_cache)
+		kmem_cache_destroy(drbd_al_ext_cache);
+
+	drbd_ee_mempool      = NULL;
+	drbd_request_mempool = NULL;
+	drbd_ee_cache        = NULL;
+	drbd_request_cache   = NULL;
+	drbd_bm_ext_cache    = NULL;
+	drbd_al_ext_cache    = NULL;
+
+	return;
+}
+
+static int drbd_create_mempools(void)
+{
+	struct page *page;
+	const int number = (DRBD_MAX_SEGMENT_SIZE/PAGE_SIZE) * minor_count;
+	int i;
+
+	/* prepare our caches and mempools */
+	drbd_request_mempool = NULL;
+	drbd_ee_cache        = NULL;
+	drbd_request_cache   = NULL;
+	drbd_bm_ext_cache    = NULL;
+	drbd_al_ext_cache    = NULL;
+	drbd_pp_pool         = NULL;
+
+	/* caches */
+	drbd_request_cache = kmem_cache_create(
+		"drbd_req", sizeof(struct drbd_request), 0, 0, NULL);
+	if (drbd_request_cache == NULL)
+		goto Enomem;
+
+	drbd_ee_cache = kmem_cache_create(
+		"drbd_ee", sizeof(struct drbd_epoch_entry), 0, 0, NULL);
+	if (drbd_ee_cache == NULL)
+		goto Enomem;
+
+	drbd_bm_ext_cache = kmem_cache_create(
+		"drbd_bm", sizeof(struct bm_extent), 0, 0, NULL);
+	if (drbd_bm_ext_cache == NULL)
+		goto Enomem;
+
+	drbd_al_ext_cache = kmem_cache_create(
+		"drbd_al", sizeof(struct lc_element), 0, 0, NULL);
+	if (drbd_al_ext_cache == NULL)
+		goto Enomem;
+
+	/* mempools */
+	drbd_request_mempool = mempool_create(number,
+		mempool_alloc_slab, mempool_free_slab, drbd_request_cache);
+	if (drbd_request_mempool == NULL)
+		goto Enomem;
+
+	drbd_ee_mempool = mempool_create(number,
+		mempool_alloc_slab, mempool_free_slab, drbd_ee_cache);
+	if (drbd_request_mempool == NULL)
+		goto Enomem;
+
+	/* drbd's page pool */
+	spin_lock_init(&drbd_pp_lock);
+
+	for (i = 0; i < number; i++) {
+		page = alloc_page(GFP_HIGHUSER);
+		if (!page)
+			goto Enomem;
+		set_page_private(page, (unsigned long)drbd_pp_pool);
+		drbd_pp_pool = page;
+	}
+	drbd_pp_vacant = number;
+
+	return 0;
+
+Enomem:
+	drbd_destroy_mempools(); /* in case we allocated some */
+	return -ENOMEM;
+}
+
+static int drbd_notify_sys(struct notifier_block *this, unsigned long code,
+	void *unused)
+{
+	/* just so we have it.  you never know what interesting things we
+	 * might want to do here some day...
+	 */
+
+	return NOTIFY_DONE;
+}
+
+static struct notifier_block drbd_notifier = {
+	.notifier_call = drbd_notify_sys,
+};
+
+static void drbd_release_ee_lists(struct drbd_conf *mdev)
+{
+	int rr;
+
+	rr = drbd_release_ee(mdev, &mdev->active_ee);
+	if (rr)
+		dev_err(DEV, "%d EEs in active list found!\n", rr);
+
+	rr = drbd_release_ee(mdev, &mdev->sync_ee);
+	if (rr)
+		dev_err(DEV, "%d EEs in sync list found!\n", rr);
+
+	rr = drbd_release_ee(mdev, &mdev->read_ee);
+	if (rr)
+		dev_err(DEV, "%d EEs in read list found!\n", rr);
+
+	rr = drbd_release_ee(mdev, &mdev->done_ee);
+	if (rr)
+		dev_err(DEV, "%d EEs in done list found!\n", rr);
+
+	rr = drbd_release_ee(mdev, &mdev->net_ee);
+	if (rr)
+		dev_err(DEV, "%d EEs in net list found!\n", rr);
+}
+
+/* caution. no locking.
+ * currently only used from module cleanup code. */
+static void drbd_delete_device(unsigned int minor)
+{
+	struct drbd_conf *mdev = minor_to_mdev(minor);
+
+	if (!mdev)
+		return;
+
+	/* paranoia asserts */
+	if (mdev->open_cnt != 0)
+		dev_err(DEV, "open_cnt = %d in %s:%u", mdev->open_cnt,
+				__FILE__ , __LINE__);
+
+	ERR_IF (!list_empty(&mdev->data.work.q)) {
+		struct list_head *lp;
+		list_for_each(lp, &mdev->data.work.q) {
+			dev_err(DEV, "lp = %p\n", lp);
+		}
+	};
+	/* end paranoia asserts */
+
+	del_gendisk(mdev->vdisk);
+
+	/* cleanup stuff that may have been allocated during
+	 * device (re-)configuration or state changes */
+
+	if (mdev->this_bdev)
+		bdput(mdev->this_bdev);
+
+	drbd_free_resources(mdev);
+
+	drbd_release_ee_lists(mdev);
+
+	/* should be free'd on disconnect? */
+	kfree(mdev->ee_hash);
+	/*
+	mdev->ee_hash_s = 0;
+	mdev->ee_hash = NULL;
+	*/
+
+	lc_destroy(mdev->act_log);
+	lc_destroy(mdev->resync);
+
+	kfree(mdev->p_uuid);
+	/* mdev->p_uuid = NULL; */
+
+	kfree(mdev->int_dig_out);
+	kfree(mdev->int_dig_in);
+	kfree(mdev->int_dig_vv);
+
+	/* cleanup the rest that has been
+	 * allocated from drbd_new_device
+	 * and actually free the mdev itself */
+	drbd_free_mdev(mdev);
+}
+
+static void drbd_cleanup(void)
+{
+	unsigned int i;
+
+	unregister_reboot_notifier(&drbd_notifier);
+
+	drbd_nl_cleanup();
+
+	if (minor_table) {
+		if (drbd_proc)
+			remove_proc_entry("drbd", NULL);
+		i = minor_count;
+		while (i--)
+			drbd_delete_device(i);
+		drbd_destroy_mempools();
+	}
+
+	kfree(minor_table);
+
+	unregister_blkdev(DRBD_MAJOR, "drbd");
+
+	printk(KERN_INFO "drbd: module cleanup done.\n");
+}
+
+/**
+ * drbd_congested() - Callback for pdflush
+ * @congested_data:	User data
+ * @bdi_bits:		Bits pdflush is currently interested in
+ *
+ * Returns 1<<BDI_async_congested and/or 1<<BDI_sync_congested if we are congested.
+ */
+static int drbd_congested(void *congested_data, int bdi_bits)
+{
+	struct drbd_conf *mdev = congested_data;
+	struct request_queue *q;
+	char reason = '-';
+	int r = 0;
+
+	if (!__inc_ap_bio_cond(mdev)) {
+		/* DRBD has frozen IO */
+		r = bdi_bits;
+		reason = 'd';
+		goto out;
+	}
+
+	if (get_ldev(mdev)) {
+		q = bdev_get_queue(mdev->ldev->backing_bdev);
+		r = bdi_congested(&q->backing_dev_info, bdi_bits);
+		put_ldev(mdev);
+		if (r)
+			reason = 'b';
+	}
+
+	if (bdi_bits & (1 << BDI_async_congested) && test_bit(NET_CONGESTED, &mdev->flags)) {
+		r |= (1 << BDI_async_congested);
+		reason = reason == 'b' ? 'a' : 'n';
+	}
+
+out:
+	mdev->congestion_reason = reason;
+	return r;
+}
+
+struct drbd_conf *drbd_new_device(unsigned int minor)
+{
+	struct drbd_conf *mdev;
+	struct gendisk *disk;
+	struct request_queue *q;
+
+	/* GFP_KERNEL, we are outside of all write-out paths */
+	mdev = kzalloc(sizeof(struct drbd_conf), GFP_KERNEL);
+	if (!mdev)
+		return NULL;
+	if (!zalloc_cpumask_var(&mdev->cpu_mask, GFP_KERNEL))
+		goto out_no_cpumask;
+
+	mdev->minor = minor;
+
+	drbd_init_set_defaults(mdev);
+
+	q = blk_alloc_queue(GFP_KERNEL);
+	if (!q)
+		goto out_no_q;
+	mdev->rq_queue = q;
+	q->queuedata   = mdev;
+	blk_queue_max_segment_size(q, DRBD_MAX_SEGMENT_SIZE);
+
+	disk = alloc_disk(1);
+	if (!disk)
+		goto out_no_disk;
+	mdev->vdisk = disk;
+
+	set_disk_ro(disk, TRUE);
+
+	disk->queue = q;
+	disk->major = DRBD_MAJOR;
+	disk->first_minor = minor;
+	disk->fops = &drbd_ops;
+	sprintf(disk->disk_name, "drbd%d", minor);
+	disk->private_data = mdev;
+
+	mdev->this_bdev = bdget(MKDEV(DRBD_MAJOR, minor));
+	/* we have no partitions. we contain only ourselves. */
+	mdev->this_bdev->bd_contains = mdev->this_bdev;
+
+	q->backing_dev_info.congested_fn = drbd_congested;
+	q->backing_dev_info.congested_data = mdev;
+
+	blk_queue_make_request(q, drbd_make_request_26);
+	blk_queue_bounce_limit(q, BLK_BOUNCE_ANY);
+	blk_queue_merge_bvec(q, drbd_merge_bvec);
+	q->queue_lock = &mdev->req_lock; /* needed since we use */
+		/* plugging on a queue, that actually has no requests! */
+	q->unplug_fn = drbd_unplug_fn;
+
+	mdev->md_io_page = alloc_page(GFP_KERNEL);
+	if (!mdev->md_io_page)
+		goto out_no_io_page;
+
+	if (drbd_bm_init(mdev))
+		goto out_no_bitmap;
+	/* no need to lock access, we are still initializing this minor device. */
+	if (!tl_init(mdev))
+		goto out_no_tl;
+
+	mdev->app_reads_hash = kzalloc(APP_R_HSIZE*sizeof(void *), GFP_KERNEL);
+	if (!mdev->app_reads_hash)
+		goto out_no_app_reads;
+
+	mdev->current_epoch = kzalloc(sizeof(struct drbd_epoch), GFP_KERNEL);
+	if (!mdev->current_epoch)
+		goto out_no_epoch;
+
+	INIT_LIST_HEAD(&mdev->current_epoch->list);
+	mdev->epochs = 1;
+
+	return mdev;
+
+/* out_whatever_else:
+	kfree(mdev->current_epoch); */
+out_no_epoch:
+	kfree(mdev->app_reads_hash);
+out_no_app_reads:
+	tl_cleanup(mdev);
+out_no_tl:
+	drbd_bm_cleanup(mdev);
+out_no_bitmap:
+	__free_page(mdev->md_io_page);
+out_no_io_page:
+	put_disk(disk);
+out_no_disk:
+	blk_cleanup_queue(q);
+out_no_q:
+	free_cpumask_var(mdev->cpu_mask);
+out_no_cpumask:
+	kfree(mdev);
+	return NULL;
+}
+
+/* counterpart of drbd_new_device.
+ * last part of drbd_delete_device. */
+void drbd_free_mdev(struct drbd_conf *mdev)
+{
+	kfree(mdev->current_epoch);
+	kfree(mdev->app_reads_hash);
+	tl_cleanup(mdev);
+	if (mdev->bitmap) /* should no longer be there. */
+		drbd_bm_cleanup(mdev);
+	__free_page(mdev->md_io_page);
+	put_disk(mdev->vdisk);
+	blk_cleanup_queue(mdev->rq_queue);
+	free_cpumask_var(mdev->cpu_mask);
+	kfree(mdev);
+}
+
+
+int __init drbd_init(void)
+{
+	int err;
+
+	if (sizeof(struct p_handshake) != 80) {
+		printk(KERN_ERR
+		       "drbd: never change the size or layout "
+		       "of the HandShake packet.\n");
+		return -EINVAL;
+	}
+
+	if (1 > minor_count || minor_count > 255) {
+		printk(KERN_ERR
+			"drbd: invalid minor_count (%d)\n", minor_count);
+#ifdef MODULE
+		return -EINVAL;
+#else
+		minor_count = 8;
+#endif
+	}
+
+	err = drbd_nl_init();
+	if (err)
+		return err;
+
+	err = register_blkdev(DRBD_MAJOR, "drbd");
+	if (err) {
+		printk(KERN_ERR
+		       "drbd: unable to register block device major %d\n",
+		       DRBD_MAJOR);
+		return err;
+	}
+
+	register_reboot_notifier(&drbd_notifier);
+
+	/*
+	 * allocate all necessary structs
+	 */
+	err = -ENOMEM;
+
+	init_waitqueue_head(&drbd_pp_wait);
+
+	drbd_proc = NULL; /* play safe for drbd_cleanup */
+	minor_table = kzalloc(sizeof(struct drbd_conf *)*minor_count,
+				GFP_KERNEL);
+	if (!minor_table)
+		goto Enomem;
+
+	err = drbd_create_mempools();
+	if (err)
+		goto Enomem;
+
+	drbd_proc = proc_create("drbd", S_IFREG | S_IRUGO , NULL, &drbd_proc_fops);
+	if (!drbd_proc)	{
+		printk(KERN_ERR "drbd: unable to register proc file\n");
+		goto Enomem;
+	}
+
+	rwlock_init(&global_state_lock);
+
+	printk(KERN_INFO "drbd: initialized. "
+	       "Version: " REL_VERSION " (api:%d/proto:%d-%d)\n",
+	       API_VERSION, PRO_VERSION_MIN, PRO_VERSION_MAX);
+	printk(KERN_INFO "drbd: %s\n", drbd_buildtag());
+	printk(KERN_INFO "drbd: registered as block device major %d\n",
+		DRBD_MAJOR);
+	printk(KERN_INFO "drbd: minor_table @ 0x%p\n", minor_table);
+
+	return 0; /* Success! */
+
+Enomem:
+	drbd_cleanup();
+	if (err == -ENOMEM)
+		/* currently always the case */
+		printk(KERN_ERR "drbd: ran out of memory\n");
+	else
+		printk(KERN_ERR "drbd: initialization failure\n");
+	return err;
+}
+
+void drbd_free_bc(struct drbd_backing_dev *ldev)
+{
+	if (ldev == NULL)
+		return;
+
+	bd_release(ldev->backing_bdev);
+	bd_release(ldev->md_bdev);
+
+	fput(ldev->lo_file);
+	fput(ldev->md_file);
+
+	kfree(ldev);
+}
+
+void drbd_free_sock(struct drbd_conf *mdev)
+{
+	if (mdev->data.socket) {
+		kernel_sock_shutdown(mdev->data.socket, SHUT_RDWR);
+		sock_release(mdev->data.socket);
+		mdev->data.socket = NULL;
+	}
+	if (mdev->meta.socket) {
+		kernel_sock_shutdown(mdev->meta.socket, SHUT_RDWR);
+		sock_release(mdev->meta.socket);
+		mdev->meta.socket = NULL;
+	}
+}
+
+
+void drbd_free_resources(struct drbd_conf *mdev)
+{
+	crypto_free_hash(mdev->csums_tfm);
+	mdev->csums_tfm = NULL;
+	crypto_free_hash(mdev->verify_tfm);
+	mdev->verify_tfm = NULL;
+	crypto_free_hash(mdev->cram_hmac_tfm);
+	mdev->cram_hmac_tfm = NULL;
+	crypto_free_hash(mdev->integrity_w_tfm);
+	mdev->integrity_w_tfm = NULL;
+	crypto_free_hash(mdev->integrity_r_tfm);
+	mdev->integrity_r_tfm = NULL;
+
+	drbd_free_sock(mdev);
+
+	__no_warn(local,
+		  drbd_free_bc(mdev->ldev);
+		  mdev->ldev = NULL;);
+}
+
+/* meta data management */
+
+struct meta_data_on_disk {
+	u64 la_size;           /* last agreed size. */
+	u64 uuid[UI_SIZE];   /* UUIDs. */
+	u64 device_uuid;
+	u64 reserved_u64_1;
+	u32 flags;             /* MDF */
+	u32 magic;
+	u32 md_size_sect;
+	u32 al_offset;         /* offset to this block */
+	u32 al_nr_extents;     /* important for restoring the AL */
+	      /* `-- act_log->nr_elements <-- sync_conf.al_extents */
+	u32 bm_offset;         /* offset to the bitmap, from here */
+	u32 bm_bytes_per_bit;  /* BM_BLOCK_SIZE */
+	u32 reserved_u32[4];
+
+} __packed;
+
+/**
+ * drbd_md_sync() - Writes the meta data super block if the MD_DIRTY flag bit is set
+ * @mdev:	DRBD device.
+ */
+void drbd_md_sync(struct drbd_conf *mdev)
+{
+	struct meta_data_on_disk *buffer;
+	sector_t sector;
+	int i;
+
+	if (!test_and_clear_bit(MD_DIRTY, &mdev->flags))
+		return;
+	del_timer(&mdev->md_sync_timer);
+
+	/* We use here D_FAILED and not D_ATTACHING because we try to write
+	 * metadata even if we detach due to a disk failure! */
+	if (!get_ldev_if_state(mdev, D_FAILED))
+		return;
+
+	trace_drbd_md_io(mdev, WRITE, mdev->ldev);
+
+	mutex_lock(&mdev->md_io_mutex);
+	buffer = (struct meta_data_on_disk *)page_address(mdev->md_io_page);
+	memset(buffer, 0, 512);
+
+	buffer->la_size = cpu_to_be64(drbd_get_capacity(mdev->this_bdev));
+	for (i = UI_CURRENT; i < UI_SIZE; i++)
+		buffer->uuid[i] = cpu_to_be64(mdev->ldev->md.uuid[i]);
+	buffer->flags = cpu_to_be32(mdev->ldev->md.flags);
+	buffer->magic = cpu_to_be32(DRBD_MD_MAGIC);
+
+	buffer->md_size_sect  = cpu_to_be32(mdev->ldev->md.md_size_sect);
+	buffer->al_offset     = cpu_to_be32(mdev->ldev->md.al_offset);
+	buffer->al_nr_extents = cpu_to_be32(mdev->act_log->nr_elements);
+	buffer->bm_bytes_per_bit = cpu_to_be32(BM_BLOCK_SIZE);
+	buffer->device_uuid = cpu_to_be64(mdev->ldev->md.device_uuid);
+
+	buffer->bm_offset = cpu_to_be32(mdev->ldev->md.bm_offset);
+
+	D_ASSERT(drbd_md_ss__(mdev, mdev->ldev) == mdev->ldev->md.md_offset);
+	sector = mdev->ldev->md.md_offset;
+
+	if (drbd_md_sync_page_io(mdev, mdev->ldev, sector, WRITE)) {
+		clear_bit(MD_DIRTY, &mdev->flags);
+	} else {
+		/* this was a try anyways ... */
+		dev_err(DEV, "meta data update failed!\n");
+
+		drbd_chk_io_error(mdev, 1, TRUE);
+	}
+
+	/* Update mdev->ldev->md.la_size_sect,
+	 * since we updated it on metadata. */
+	mdev->ldev->md.la_size_sect = drbd_get_capacity(mdev->this_bdev);
+
+	mutex_unlock(&mdev->md_io_mutex);
+	put_ldev(mdev);
+}
+
+/**
+ * drbd_md_read() - Reads in the meta data super block
+ * @mdev:	DRBD device.
+ * @bdev:	Device from which the meta data should be read in.
+ *
+ * Return 0 (NO_ERROR) on success, and an enum drbd_ret_codes in case
+ * something goes wrong.  Currently only: ERR_IO_MD_DISK, ERR_MD_INVALID.
+ */
+int drbd_md_read(struct drbd_conf *mdev, struct drbd_backing_dev *bdev)
+{
+	struct meta_data_on_disk *buffer;
+	int i, rv = NO_ERROR;
+
+	if (!get_ldev_if_state(mdev, D_ATTACHING))
+		return ERR_IO_MD_DISK;
+
+	trace_drbd_md_io(mdev, READ, bdev);
+
+	mutex_lock(&mdev->md_io_mutex);
+	buffer = (struct meta_data_on_disk *)page_address(mdev->md_io_page);
+
+	if (!drbd_md_sync_page_io(mdev, bdev, bdev->md.md_offset, READ)) {
+		/* NOTE: cant do normal error processing here as this is
+		   called BEFORE disk is attached */
+		dev_err(DEV, "Error while reading metadata.\n");
+		rv = ERR_IO_MD_DISK;
+		goto err;
+	}
+
+	if (be32_to_cpu(buffer->magic) != DRBD_MD_MAGIC) {
+		dev_err(DEV, "Error while reading metadata, magic not found.\n");
+		rv = ERR_MD_INVALID;
+		goto err;
+	}
+	if (be32_to_cpu(buffer->al_offset) != bdev->md.al_offset) {
+		dev_err(DEV, "unexpected al_offset: %d (expected %d)\n",
+		    be32_to_cpu(buffer->al_offset), bdev->md.al_offset);
+		rv = ERR_MD_INVALID;
+		goto err;
+	}
+	if (be32_to_cpu(buffer->bm_offset) != bdev->md.bm_offset) {
+		dev_err(DEV, "unexpected bm_offset: %d (expected %d)\n",
+		    be32_to_cpu(buffer->bm_offset), bdev->md.bm_offset);
+		rv = ERR_MD_INVALID;
+		goto err;
+	}
+	if (be32_to_cpu(buffer->md_size_sect) != bdev->md.md_size_sect) {
+		dev_err(DEV, "unexpected md_size: %u (expected %u)\n",
+		    be32_to_cpu(buffer->md_size_sect), bdev->md.md_size_sect);
+		rv = ERR_MD_INVALID;
+		goto err;
+	}
+
+	if (be32_to_cpu(buffer->bm_bytes_per_bit) != BM_BLOCK_SIZE) {
+		dev_err(DEV, "unexpected bm_bytes_per_bit: %u (expected %u)\n",
+		    be32_to_cpu(buffer->bm_bytes_per_bit), BM_BLOCK_SIZE);
+		rv = ERR_MD_INVALID;
+		goto err;
+	}
+
+	bdev->md.la_size_sect = be64_to_cpu(buffer->la_size);
+	for (i = UI_CURRENT; i < UI_SIZE; i++)
+		bdev->md.uuid[i] = be64_to_cpu(buffer->uuid[i]);
+	bdev->md.flags = be32_to_cpu(buffer->flags);
+	mdev->sync_conf.al_extents = be32_to_cpu(buffer->al_nr_extents);
+	bdev->md.device_uuid = be64_to_cpu(buffer->device_uuid);
+
+	if (mdev->sync_conf.al_extents < 7)
+		mdev->sync_conf.al_extents = 127;
+
+ err:
+	mutex_unlock(&mdev->md_io_mutex);
+	put_ldev(mdev);
+
+	return rv;
+}
+
+/**
+ * drbd_md_mark_dirty() - Mark meta data super block as dirty
+ * @mdev:	DRBD device.
+ *
+ * Call this function if you change anything that should be written to
+ * the meta-data super block. This function sets MD_DIRTY, and starts a
+ * timer that ensures that within five seconds you have to call drbd_md_sync().
+ */
+void drbd_md_mark_dirty(struct drbd_conf *mdev)
+{
+	set_bit(MD_DIRTY, &mdev->flags);
+	mod_timer(&mdev->md_sync_timer, jiffies + 5*HZ);
+}
+
+
+static void drbd_uuid_move_history(struct drbd_conf *mdev) __must_hold(local)
+{
+	int i;
+
+	for (i = UI_HISTORY_START; i < UI_HISTORY_END; i++) {
+		mdev->ldev->md.uuid[i+1] = mdev->ldev->md.uuid[i];
+
+		trace_drbd_uuid(mdev, i+1);
+	}
+}
+
+void _drbd_uuid_set(struct drbd_conf *mdev, int idx, u64 val) __must_hold(local)
+{
+	if (idx == UI_CURRENT) {
+		if (mdev->state.role == R_PRIMARY)
+			val |= 1;
+		else
+			val &= ~((u64)1);
+
+		drbd_set_ed_uuid(mdev, val);
+	}
+
+	mdev->ldev->md.uuid[idx] = val;
+	trace_drbd_uuid(mdev, idx);
+	drbd_md_mark_dirty(mdev);
+}
+
+
+void drbd_uuid_set(struct drbd_conf *mdev, int idx, u64 val) __must_hold(local)
+{
+	if (mdev->ldev->md.uuid[idx]) {
+		drbd_uuid_move_history(mdev);
+		mdev->ldev->md.uuid[UI_HISTORY_START] = mdev->ldev->md.uuid[idx];
+		trace_drbd_uuid(mdev, UI_HISTORY_START);
+	}
+	_drbd_uuid_set(mdev, idx, val);
+}
+
+/**
+ * drbd_uuid_new_current() - Creates a new current UUID
+ * @mdev:	DRBD device.
+ *
+ * Creates a new current UUID, and rotates the old current UUID into
+ * the bitmap slot. Causes an incremental resync upon next connect.
+ */
+void drbd_uuid_new_current(struct drbd_conf *mdev) __must_hold(local)
+{
+	u64 val;
+
+	dev_info(DEV, "Creating new current UUID\n");
+	D_ASSERT(mdev->ldev->md.uuid[UI_BITMAP] == 0);
+	mdev->ldev->md.uuid[UI_BITMAP] = mdev->ldev->md.uuid[UI_CURRENT];
+	trace_drbd_uuid(mdev, UI_BITMAP);
+
+	get_random_bytes(&val, sizeof(u64));
+	_drbd_uuid_set(mdev, UI_CURRENT, val);
+}
+
+void drbd_uuid_set_bm(struct drbd_conf *mdev, u64 val) __must_hold(local)
+{
+	if (mdev->ldev->md.uuid[UI_BITMAP] == 0 && val == 0)
+		return;
+
+	if (val == 0) {
+		drbd_uuid_move_history(mdev);
+		mdev->ldev->md.uuid[UI_HISTORY_START] = mdev->ldev->md.uuid[UI_BITMAP];
+		mdev->ldev->md.uuid[UI_BITMAP] = 0;
+		trace_drbd_uuid(mdev, UI_HISTORY_START);
+		trace_drbd_uuid(mdev, UI_BITMAP);
+	} else {
+		if (mdev->ldev->md.uuid[UI_BITMAP])
+			dev_warn(DEV, "bm UUID already set");
+
+		mdev->ldev->md.uuid[UI_BITMAP] = val;
+		mdev->ldev->md.uuid[UI_BITMAP] &= ~((u64)1);
+
+		trace_drbd_uuid(mdev, UI_BITMAP);
+	}
+	drbd_md_mark_dirty(mdev);
+}
+
+/**
+ * drbd_bmio_set_n_write() - io_fn for drbd_queue_bitmap_io() or drbd_bitmap_io()
+ * @mdev:	DRBD device.
+ *
+ * Sets all bits in the bitmap and writes the whole bitmap to stable storage.
+ */
+int drbd_bmio_set_n_write(struct drbd_conf *mdev)
+{
+	int rv = -EIO;
+
+	if (get_ldev_if_state(mdev, D_ATTACHING)) {
+		drbd_md_set_flag(mdev, MDF_FULL_SYNC);
+		drbd_md_sync(mdev);
+		drbd_bm_set_all(mdev);
+
+		rv = drbd_bm_write(mdev);
+
+		if (!rv) {
+			drbd_md_clear_flag(mdev, MDF_FULL_SYNC);
+			drbd_md_sync(mdev);
+		}
+
+		put_ldev(mdev);
+	}
+
+	return rv;
+}
+
+/**
+ * drbd_bmio_clear_n_write() - io_fn for drbd_queue_bitmap_io() or drbd_bitmap_io()
+ * @mdev:	DRBD device.
+ *
+ * Clears all bits in the bitmap and writes the whole bitmap to stable storage.
+ */
+int drbd_bmio_clear_n_write(struct drbd_conf *mdev)
+{
+	int rv = -EIO;
+
+	if (get_ldev_if_state(mdev, D_ATTACHING)) {
+		drbd_bm_clear_all(mdev);
+		rv = drbd_bm_write(mdev);
+		put_ldev(mdev);
+	}
+
+	return rv;
+}
+
+static int w_bitmap_io(struct drbd_conf *mdev, struct drbd_work *w, int unused)
+{
+	struct bm_io_work *work = container_of(w, struct bm_io_work, w);
+	int rv;
+
+	D_ASSERT(atomic_read(&mdev->ap_bio_cnt) == 0);
+
+	drbd_bm_lock(mdev, work->why);
+	rv = work->io_fn(mdev);
+	drbd_bm_unlock(mdev);
+
+	clear_bit(BITMAP_IO, &mdev->flags);
+	wake_up(&mdev->misc_wait);
+
+	if (work->done)
+		work->done(mdev, rv);
+
+	clear_bit(BITMAP_IO_QUEUED, &mdev->flags);
+	work->why = NULL;
+
+	return 1;
+}
+
+/**
+ * drbd_queue_bitmap_io() - Queues an IO operation on the whole bitmap
+ * @mdev:	DRBD device.
+ * @io_fn:	IO callback to be called when bitmap IO is possible
+ * @done:	callback to be called after the bitmap IO was performed
+ * @why:	Descriptive text of the reason for doing the IO
+ *
+ * While IO on the bitmap happens we freeze application IO thus we ensure
+ * that drbd_set_out_of_sync() can not be called. This function MAY ONLY be
+ * called from worker context. It MUST NOT be used while a previous such
+ * work is still pending!
+ */
+void drbd_queue_bitmap_io(struct drbd_conf *mdev,
+			  int (*io_fn)(struct drbd_conf *),
+			  void (*done)(struct drbd_conf *, int),
+			  char *why)
+{
+	D_ASSERT(current == mdev->worker.task);
+
+	D_ASSERT(!test_bit(BITMAP_IO_QUEUED, &mdev->flags));
+	D_ASSERT(!test_bit(BITMAP_IO, &mdev->flags));
+	D_ASSERT(list_empty(&mdev->bm_io_work.w.list));
+	if (mdev->bm_io_work.why)
+		dev_err(DEV, "FIXME going to queue '%s' but '%s' still pending?\n",
+			why, mdev->bm_io_work.why);
+
+	mdev->bm_io_work.io_fn = io_fn;
+	mdev->bm_io_work.done = done;
+	mdev->bm_io_work.why = why;
+
+	set_bit(BITMAP_IO, &mdev->flags);
+	if (atomic_read(&mdev->ap_bio_cnt) == 0) {
+		if (list_empty(&mdev->bm_io_work.w.list)) {
+			set_bit(BITMAP_IO_QUEUED, &mdev->flags);
+			drbd_queue_work(&mdev->data.work, &mdev->bm_io_work.w);
+		} else
+			dev_err(DEV, "FIXME avoided double queuing bm_io_work\n");
+	}
+}
+
+/**
+ * drbd_bitmap_io() -  Does an IO operation on the whole bitmap
+ * @mdev:	DRBD device.
+ * @io_fn:	IO callback to be called when bitmap IO is possible
+ * @why:	Descriptive text of the reason for doing the IO
+ *
+ * freezes application IO while that the actual IO operations runs. This
+ * functions MAY NOT be called from worker context.
+ */
+int drbd_bitmap_io(struct drbd_conf *mdev, int (*io_fn)(struct drbd_conf *), char *why)
+{
+	int rv;
+
+	D_ASSERT(current != mdev->worker.task);
+
+	drbd_suspend_io(mdev);
+
+	drbd_bm_lock(mdev, why);
+	rv = io_fn(mdev);
+	drbd_bm_unlock(mdev);
+
+	drbd_resume_io(mdev);
+
+	return rv;
+}
+
+void drbd_md_set_flag(struct drbd_conf *mdev, int flag) __must_hold(local)
+{
+	if ((mdev->ldev->md.flags & flag) != flag) {
+		drbd_md_mark_dirty(mdev);
+		mdev->ldev->md.flags |= flag;
+	}
+}
+
+void drbd_md_clear_flag(struct drbd_conf *mdev, int flag) __must_hold(local)
+{
+	if ((mdev->ldev->md.flags & flag) != 0) {
+		drbd_md_mark_dirty(mdev);
+		mdev->ldev->md.flags &= ~flag;
+	}
+}
+int drbd_md_test_flag(struct drbd_backing_dev *bdev, int flag)
+{
+	return (bdev->md.flags & flag) != 0;
+}
+
+static void md_sync_timer_fn(unsigned long data)
+{
+	struct drbd_conf *mdev = (struct drbd_conf *) data;
+
+	drbd_queue_work_front(&mdev->data.work, &mdev->md_sync_work);
+}
+
+static int w_md_sync(struct drbd_conf *mdev, struct drbd_work *w, int unused)
+{
+	dev_warn(DEV, "md_sync_timer expired! Worker calls drbd_md_sync().\n");
+	drbd_md_sync(mdev);
+
+	return 1;
+}
+
+#ifdef CONFIG_DRBD_FAULT_INJECTION
+/* Fault insertion support including random number generator shamelessly
+ * stolen from kernel/rcutorture.c */
+struct fault_random_state {
+	unsigned long state;
+	unsigned long count;
+};
+
+#define FAULT_RANDOM_MULT 39916801  /* prime */
+#define FAULT_RANDOM_ADD	479001701 /* prime */
+#define FAULT_RANDOM_REFRESH 10000
+
+/*
+ * Crude but fast random-number generator.  Uses a linear congruential
+ * generator, with occasional help from get_random_bytes().
+ */
+static unsigned long
+_drbd_fault_random(struct fault_random_state *rsp)
+{
+	long refresh;
+
+	if (--rsp->count < 0) {
+		get_random_bytes(&refresh, sizeof(refresh));
+		rsp->state += refresh;
+		rsp->count = FAULT_RANDOM_REFRESH;
+	}
+	rsp->state = rsp->state * FAULT_RANDOM_MULT + FAULT_RANDOM_ADD;
+	return swahw32(rsp->state);
+}
+
+static char *
+_drbd_fault_str(unsigned int type) {
+	static char *_faults[] = {
+		[DRBD_FAULT_MD_WR] = "Meta-data write",
+		[DRBD_FAULT_MD_RD] = "Meta-data read",
+		[DRBD_FAULT_RS_WR] = "Resync write",
+		[DRBD_FAULT_RS_RD] = "Resync read",
+		[DRBD_FAULT_DT_WR] = "Data write",
+		[DRBD_FAULT_DT_RD] = "Data read",
+		[DRBD_FAULT_DT_RA] = "Data read ahead",
+		[DRBD_FAULT_BM_ALLOC] = "BM allocation",
+		[DRBD_FAULT_AL_EE] = "EE allocation"
+	};
+
+	return (type < DRBD_FAULT_MAX) ? _faults[type] : "**Unknown**";
+}
+
+unsigned int
+_drbd_insert_fault(struct drbd_conf *mdev, unsigned int type)
+{
+	static struct fault_random_state rrs = {0, 0};
+
+	unsigned int ret = (
+		(fault_devs == 0 ||
+			((1 << mdev_to_minor(mdev)) & fault_devs) != 0) &&
+		(((_drbd_fault_random(&rrs) % 100) + 1) <= fault_rate));
+
+	if (ret) {
+		fault_count++;
+
+		if (printk_ratelimit())
+			dev_warn(DEV, "***Simulating %s failure\n",
+				_drbd_fault_str(type));
+	}
+
+	return ret;
+}
+#endif
+
+const char *drbd_buildtag(void)
+{
+	/* DRBD built from external sources has here a reference to the
+	   git hash of the source code. */
+
+	static char buildtag[38] = "\0uilt-in";
+
+	if (buildtag[0] == 0) {
+#ifdef CONFIG_MODULES
+		if (THIS_MODULE != NULL)
+			sprintf(buildtag, "srcversion: %-24s", THIS_MODULE->srcversion);
+		else
+#endif
+			buildtag[0] = 'b';
+	}
+
+	return buildtag;
+}
+
+module_init(drbd_init)
+module_exit(drbd_cleanup)
+
+/* For drbd_tracing: */
+EXPORT_SYMBOL(drbd_conn_str);
+EXPORT_SYMBOL(drbd_role_str);
+EXPORT_SYMBOL(drbd_disk_str);
+EXPORT_SYMBOL(drbd_set_st_err_str);
diff --git a/drivers/block/drbd/drbd_nl.c b/drivers/block/drbd/drbd_nl.c
new file mode 100644
index 00000000000..1927acefe23
--- /dev/null
+++ b/drivers/block/drbd/drbd_nl.c
@@ -0,0 +1,2365 @@
+/*
+   drbd_nl.c
+
+   This file is part of DRBD by Philipp Reisner and Lars Ellenberg.
+
+   Copyright (C) 2001-2008, LINBIT Information Technologies GmbH.
+   Copyright (C) 1999-2008, Philipp Reisner <philipp.reisner@linbit.com>.
+   Copyright (C) 2002-2008, Lars Ellenberg <lars.ellenberg@linbit.com>.
+
+   drbd is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 2, or (at your option)
+   any later version.
+
+   drbd is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with drbd; see the file COPYING.  If not, write to
+   the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
+
+ */
+
+#include <linux/autoconf.h>
+#include <linux/module.h>
+#include <linux/drbd.h>
+#include <linux/in.h>
+#include <linux/fs.h>
+#include <linux/file.h>
+#include <linux/slab.h>
+#include <linux/connector.h>
+#include <linux/blkpg.h>
+#include <linux/cpumask.h>
+#include "drbd_int.h"
+#include "drbd_tracing.h"
+#include "drbd_wrappers.h"
+#include <asm/unaligned.h>
+#include <linux/drbd_tag_magic.h>
+#include <linux/drbd_limits.h>
+
+static unsigned short *tl_add_blob(unsigned short *, enum drbd_tags, const void *, int);
+static unsigned short *tl_add_str(unsigned short *, enum drbd_tags, const char *);
+static unsigned short *tl_add_int(unsigned short *, enum drbd_tags, const void *);
+
+/* see get_sb_bdev and bd_claim */
+static char *drbd_m_holder = "Hands off! this is DRBD's meta data device.";
+
+/* Generate the tag_list to struct functions */
+#define NL_PACKET(name, number, fields) \
+static int name ## _from_tags(struct drbd_conf *mdev, \
+	unsigned short *tags, struct name *arg) __attribute__ ((unused)); \
+static int name ## _from_tags(struct drbd_conf *mdev, \
+	unsigned short *tags, struct name *arg) \
+{ \
+	int tag; \
+	int dlen; \
+	\
+	while ((tag = get_unaligned(tags++)) != TT_END) {	\
+		dlen = get_unaligned(tags++);			\
+		switch (tag_number(tag)) { \
+		fields \
+		default: \
+			if (tag & T_MANDATORY) { \
+				dev_err(DEV, "Unknown tag: %d\n", tag_number(tag)); \
+				return 0; \
+			} \
+		} \
+		tags = (unsigned short *)((char *)tags + dlen); \
+	} \
+	return 1; \
+}
+#define NL_INTEGER(pn, pr, member) \
+	case pn: /* D_ASSERT( tag_type(tag) == TT_INTEGER ); */ \
+		arg->member = get_unaligned((int *)(tags));	\
+		break;
+#define NL_INT64(pn, pr, member) \
+	case pn: /* D_ASSERT( tag_type(tag) == TT_INT64 ); */ \
+		arg->member = get_unaligned((u64 *)(tags));	\
+		break;
+#define NL_BIT(pn, pr, member) \
+	case pn: /* D_ASSERT( tag_type(tag) == TT_BIT ); */ \
+		arg->member = *(char *)(tags) ? 1 : 0; \
+		break;
+#define NL_STRING(pn, pr, member, len) \
+	case pn: /* D_ASSERT( tag_type(tag) == TT_STRING ); */ \
+		if (dlen > len) { \
+			dev_err(DEV, "arg too long: %s (%u wanted, max len: %u bytes)\n", \
+				#member, dlen, (unsigned int)len); \
+			return 0; \
+		} \
+		 arg->member ## _len = dlen; \
+		 memcpy(arg->member, tags, min_t(size_t, dlen, len)); \
+		 break;
+#include "linux/drbd_nl.h"
+
+/* Generate the struct to tag_list functions */
+#define NL_PACKET(name, number, fields) \
+static unsigned short* \
+name ## _to_tags(struct drbd_conf *mdev, \
+	struct name *arg, unsigned short *tags) __attribute__ ((unused)); \
+static unsigned short* \
+name ## _to_tags(struct drbd_conf *mdev, \
+	struct name *arg, unsigned short *tags) \
+{ \
+	fields \
+	return tags; \
+}
+
+#define NL_INTEGER(pn, pr, member) \
+	put_unaligned(pn | pr | TT_INTEGER, tags++);	\
+	put_unaligned(sizeof(int), tags++);		\
+	put_unaligned(arg->member, (int *)tags);	\
+	tags = (unsigned short *)((char *)tags+sizeof(int));
+#define NL_INT64(pn, pr, member) \
+	put_unaligned(pn | pr | TT_INT64, tags++);	\
+	put_unaligned(sizeof(u64), tags++);		\
+	put_unaligned(arg->member, (u64 *)tags);	\
+	tags = (unsigned short *)((char *)tags+sizeof(u64));
+#define NL_BIT(pn, pr, member) \
+	put_unaligned(pn | pr | TT_BIT, tags++);	\
+	put_unaligned(sizeof(char), tags++);		\
+	*(char *)tags = arg->member; \
+	tags = (unsigned short *)((char *)tags+sizeof(char));
+#define NL_STRING(pn, pr, member, len) \
+	put_unaligned(pn | pr | TT_STRING, tags++);	\
+	put_unaligned(arg->member ## _len, tags++);	\
+	memcpy(tags, arg->member, arg->member ## _len); \
+	tags = (unsigned short *)((char *)tags + arg->member ## _len);
+#include "linux/drbd_nl.h"
+
+void drbd_bcast_ev_helper(struct drbd_conf *mdev, char *helper_name);
+void drbd_nl_send_reply(struct cn_msg *, int);
+
+int drbd_khelper(struct drbd_conf *mdev, char *cmd)
+{
+	char *envp[] = { "HOME=/",
+			"TERM=linux",
+			"PATH=/sbin:/usr/sbin:/bin:/usr/bin",
+			NULL, /* Will be set to address family */
+			NULL, /* Will be set to address */
+			NULL };
+
+	char mb[12], af[20], ad[60], *afs;
+	char *argv[] = {usermode_helper, cmd, mb, NULL };
+	int ret;
+
+	snprintf(mb, 12, "minor-%d", mdev_to_minor(mdev));
+
+	if (get_net_conf(mdev)) {
+		switch (((struct sockaddr *)mdev->net_conf->peer_addr)->sa_family) {
+		case AF_INET6:
+			afs = "ipv6";
+			snprintf(ad, 60, "DRBD_PEER_ADDRESS=%pI6",
+				 &((struct sockaddr_in6 *)mdev->net_conf->peer_addr)->sin6_addr);
+			break;
+		case AF_INET:
+			afs = "ipv4";
+			snprintf(ad, 60, "DRBD_PEER_ADDRESS=%pI4",
+				 &((struct sockaddr_in *)mdev->net_conf->peer_addr)->sin_addr);
+			break;
+		default:
+			afs = "ssocks";
+			snprintf(ad, 60, "DRBD_PEER_ADDRESS=%pI4",
+				 &((struct sockaddr_in *)mdev->net_conf->peer_addr)->sin_addr);
+		}
+		snprintf(af, 20, "DRBD_PEER_AF=%s", afs);
+		envp[3]=af;
+		envp[4]=ad;
+		put_net_conf(mdev);
+	}
+
+	dev_info(DEV, "helper command: %s %s %s\n", usermode_helper, cmd, mb);
+
+	drbd_bcast_ev_helper(mdev, cmd);
+	ret = call_usermodehelper(usermode_helper, argv, envp, 1);
+	if (ret)
+		dev_warn(DEV, "helper command: %s %s %s exit code %u (0x%x)\n",
+				usermode_helper, cmd, mb,
+				(ret >> 8) & 0xff, ret);
+	else
+		dev_info(DEV, "helper command: %s %s %s exit code %u (0x%x)\n",
+				usermode_helper, cmd, mb,
+				(ret >> 8) & 0xff, ret);
+
+	if (ret < 0) /* Ignore any ERRNOs we got. */
+		ret = 0;
+
+	return ret;
+}
+
+enum drbd_disk_state drbd_try_outdate_peer(struct drbd_conf *mdev)
+{
+	char *ex_to_string;
+	int r;
+	enum drbd_disk_state nps;
+	enum drbd_fencing_p fp;
+
+	D_ASSERT(mdev->state.pdsk == D_UNKNOWN);
+
+	if (get_ldev_if_state(mdev, D_CONSISTENT)) {
+		fp = mdev->ldev->dc.fencing;
+		put_ldev(mdev);
+	} else {
+		dev_warn(DEV, "Not fencing peer, I'm not even Consistent myself.\n");
+		return mdev->state.pdsk;
+	}
+
+	if (fp == FP_STONITH)
+		_drbd_request_state(mdev, NS(susp, 1), CS_WAIT_COMPLETE);
+
+	r = drbd_khelper(mdev, "fence-peer");
+
+	switch ((r>>8) & 0xff) {
+	case 3: /* peer is inconsistent */
+		ex_to_string = "peer is inconsistent or worse";
+		nps = D_INCONSISTENT;
+		break;
+	case 4: /* peer got outdated, or was already outdated */
+		ex_to_string = "peer was fenced";
+		nps = D_OUTDATED;
+		break;
+	case 5: /* peer was down */
+		if (mdev->state.disk == D_UP_TO_DATE) {
+			/* we will(have) create(d) a new UUID anyways... */
+			ex_to_string = "peer is unreachable, assumed to be dead";
+			nps = D_OUTDATED;
+		} else {
+			ex_to_string = "peer unreachable, doing nothing since disk != UpToDate";
+			nps = mdev->state.pdsk;
+		}
+		break;
+	case 6: /* Peer is primary, voluntarily outdate myself.
+		 * This is useful when an unconnected R_SECONDARY is asked to
+		 * become R_PRIMARY, but finds the other peer being active. */
+		ex_to_string = "peer is active";
+		dev_warn(DEV, "Peer is primary, outdating myself.\n");
+		nps = D_UNKNOWN;
+		_drbd_request_state(mdev, NS(disk, D_OUTDATED), CS_WAIT_COMPLETE);
+		break;
+	case 7:
+		if (fp != FP_STONITH)
+			dev_err(DEV, "fence-peer() = 7 && fencing != Stonith !!!\n");
+		ex_to_string = "peer was stonithed";
+		nps = D_OUTDATED;
+		break;
+	default:
+		/* The script is broken ... */
+		nps = D_UNKNOWN;
+		dev_err(DEV, "fence-peer helper broken, returned %d\n", (r>>8)&0xff);
+		return nps;
+	}
+
+	dev_info(DEV, "fence-peer helper returned %d (%s)\n",
+			(r>>8) & 0xff, ex_to_string);
+	return nps;
+}
+
+
+int drbd_set_role(struct drbd_conf *mdev, enum drbd_role new_role, int force)
+{
+	const int max_tries = 4;
+	int r = 0;
+	int try = 0;
+	int forced = 0;
+	union drbd_state mask, val;
+	enum drbd_disk_state nps;
+
+	if (new_role == R_PRIMARY)
+		request_ping(mdev); /* Detect a dead peer ASAP */
+
+	mutex_lock(&mdev->state_mutex);
+
+	mask.i = 0; mask.role = R_MASK;
+	val.i  = 0; val.role  = new_role;
+
+	while (try++ < max_tries) {
+		r = _drbd_request_state(mdev, mask, val, CS_WAIT_COMPLETE);
+
+		/* in case we first succeeded to outdate,
+		 * but now suddenly could establish a connection */
+		if (r == SS_CW_FAILED_BY_PEER && mask.pdsk != 0) {
+			val.pdsk = 0;
+			mask.pdsk = 0;
+			continue;
+		}
+
+		if (r == SS_NO_UP_TO_DATE_DISK && force &&
+		    (mdev->state.disk == D_INCONSISTENT ||
+		     mdev->state.disk == D_OUTDATED)) {
+			mask.disk = D_MASK;
+			val.disk  = D_UP_TO_DATE;
+			forced = 1;
+			continue;
+		}
+
+		if (r == SS_NO_UP_TO_DATE_DISK &&
+		    mdev->state.disk == D_CONSISTENT && mask.pdsk == 0) {
+			D_ASSERT(mdev->state.pdsk == D_UNKNOWN);
+			nps = drbd_try_outdate_peer(mdev);
+
+			if (nps == D_OUTDATED || nps == D_INCONSISTENT) {
+				val.disk = D_UP_TO_DATE;
+				mask.disk = D_MASK;
+			}
+
+			val.pdsk = nps;
+			mask.pdsk = D_MASK;
+
+			continue;
+		}
+
+		if (r == SS_NOTHING_TO_DO)
+			goto fail;
+		if (r == SS_PRIMARY_NOP && mask.pdsk == 0) {
+			nps = drbd_try_outdate_peer(mdev);
+
+			if (force && nps > D_OUTDATED) {
+				dev_warn(DEV, "Forced into split brain situation!\n");
+				nps = D_OUTDATED;
+			}
+
+			mask.pdsk = D_MASK;
+			val.pdsk  = nps;
+
+			continue;
+		}
+		if (r == SS_TWO_PRIMARIES) {
+			/* Maybe the peer is detected as dead very soon...
+			   retry at most once more in this case. */
+			__set_current_state(TASK_INTERRUPTIBLE);
+			schedule_timeout((mdev->net_conf->ping_timeo+1)*HZ/10);
+			if (try < max_tries)
+				try = max_tries - 1;
+			continue;
+		}
+		if (r < SS_SUCCESS) {
+			r = _drbd_request_state(mdev, mask, val,
+						CS_VERBOSE + CS_WAIT_COMPLETE);
+			if (r < SS_SUCCESS)
+				goto fail;
+		}
+		break;
+	}
+
+	if (r < SS_SUCCESS)
+		goto fail;
+
+	if (forced)
+		dev_warn(DEV, "Forced to consider local data as UpToDate!\n");
+
+	/* Wait until nothing is on the fly :) */
+	wait_event(mdev->misc_wait, atomic_read(&mdev->ap_pending_cnt) == 0);
+
+	if (new_role == R_SECONDARY) {
+		set_disk_ro(mdev->vdisk, TRUE);
+		if (get_ldev(mdev)) {
+			mdev->ldev->md.uuid[UI_CURRENT] &= ~(u64)1;
+			put_ldev(mdev);
+		}
+	} else {
+		if (get_net_conf(mdev)) {
+			mdev->net_conf->want_lose = 0;
+			put_net_conf(mdev);
+		}
+		set_disk_ro(mdev->vdisk, FALSE);
+		if (get_ldev(mdev)) {
+			if (((mdev->state.conn < C_CONNECTED ||
+			       mdev->state.pdsk <= D_FAILED)
+			      && mdev->ldev->md.uuid[UI_BITMAP] == 0) || forced)
+				drbd_uuid_new_current(mdev);
+
+			mdev->ldev->md.uuid[UI_CURRENT] |=  (u64)1;
+			put_ldev(mdev);
+		}
+	}
+
+	if ((new_role == R_SECONDARY) && get_ldev(mdev)) {
+		drbd_al_to_on_disk_bm(mdev);
+		put_ldev(mdev);
+	}
+
+	if (mdev->state.conn >= C_WF_REPORT_PARAMS) {
+		/* if this was forced, we should consider sync */
+		if (forced)
+			drbd_send_uuids(mdev);
+		drbd_send_state(mdev);
+	}
+
+	drbd_md_sync(mdev);
+
+	kobject_uevent(&disk_to_dev(mdev->vdisk)->kobj, KOBJ_CHANGE);
+ fail:
+	mutex_unlock(&mdev->state_mutex);
+	return r;
+}
+
+
+static int drbd_nl_primary(struct drbd_conf *mdev, struct drbd_nl_cfg_req *nlp,
+			   struct drbd_nl_cfg_reply *reply)
+{
+	struct primary primary_args;
+
+	memset(&primary_args, 0, sizeof(struct primary));
+	if (!primary_from_tags(mdev, nlp->tag_list, &primary_args)) {
+		reply->ret_code = ERR_MANDATORY_TAG;
+		return 0;
+	}
+
+	reply->ret_code =
+		drbd_set_role(mdev, R_PRIMARY, primary_args.overwrite_peer);
+
+	return 0;
+}
+
+static int drbd_nl_secondary(struct drbd_conf *mdev, struct drbd_nl_cfg_req *nlp,
+			     struct drbd_nl_cfg_reply *reply)
+{
+	reply->ret_code = drbd_set_role(mdev, R_SECONDARY, 0);
+
+	return 0;
+}
+
+/* initializes the md.*_offset members, so we are able to find
+ * the on disk meta data */
+static void drbd_md_set_sector_offsets(struct drbd_conf *mdev,
+				       struct drbd_backing_dev *bdev)
+{
+	sector_t md_size_sect = 0;
+	switch (bdev->dc.meta_dev_idx) {
+	default:
+		/* v07 style fixed size indexed meta data */
+		bdev->md.md_size_sect = MD_RESERVED_SECT;
+		bdev->md.md_offset = drbd_md_ss__(mdev, bdev);
+		bdev->md.al_offset = MD_AL_OFFSET;
+		bdev->md.bm_offset = MD_BM_OFFSET;
+		break;
+	case DRBD_MD_INDEX_FLEX_EXT:
+		/* just occupy the full device; unit: sectors */
+		bdev->md.md_size_sect = drbd_get_capacity(bdev->md_bdev);
+		bdev->md.md_offset = 0;
+		bdev->md.al_offset = MD_AL_OFFSET;
+		bdev->md.bm_offset = MD_BM_OFFSET;
+		break;
+	case DRBD_MD_INDEX_INTERNAL:
+	case DRBD_MD_INDEX_FLEX_INT:
+		bdev->md.md_offset = drbd_md_ss__(mdev, bdev);
+		/* al size is still fixed */
+		bdev->md.al_offset = -MD_AL_MAX_SIZE;
+		/* we need (slightly less than) ~ this much bitmap sectors: */
+		md_size_sect = drbd_get_capacity(bdev->backing_bdev);
+		md_size_sect = ALIGN(md_size_sect, BM_SECT_PER_EXT);
+		md_size_sect = BM_SECT_TO_EXT(md_size_sect);
+		md_size_sect = ALIGN(md_size_sect, 8);
+
+		/* plus the "drbd meta data super block",
+		 * and the activity log; */
+		md_size_sect += MD_BM_OFFSET;
+
+		bdev->md.md_size_sect = md_size_sect;
+		/* bitmap offset is adjusted by 'super' block size */
+		bdev->md.bm_offset   = -md_size_sect + MD_AL_OFFSET;
+		break;
+	}
+}
+
+char *ppsize(char *buf, unsigned long long size)
+{
+	/* Needs 9 bytes at max. */
+	static char units[] = { 'K', 'M', 'G', 'T', 'P', 'E' };
+	int base = 0;
+	while (size >= 10000) {
+		/* shift + round */
+		size = (size >> 10) + !!(size & (1<<9));
+		base++;
+	}
+	sprintf(buf, "%lu %cB", (long)size, units[base]);
+
+	return buf;
+}
+
+/* there is still a theoretical deadlock when called from receiver
+ * on an D_INCONSISTENT R_PRIMARY:
+ *  remote READ does inc_ap_bio, receiver would need to receive answer
+ *  packet from remote to dec_ap_bio again.
+ *  receiver receive_sizes(), comes here,
+ *  waits for ap_bio_cnt == 0. -> deadlock.
+ * but this cannot happen, actually, because:
+ *  R_PRIMARY D_INCONSISTENT, and peer's disk is unreachable
+ *  (not connected, or bad/no disk on peer):
+ *  see drbd_fail_request_early, ap_bio_cnt is zero.
+ *  R_PRIMARY D_INCONSISTENT, and C_SYNC_TARGET:
+ *  peer may not initiate a resize.
+ */
+void drbd_suspend_io(struct drbd_conf *mdev)
+{
+	set_bit(SUSPEND_IO, &mdev->flags);
+	wait_event(mdev->misc_wait, !atomic_read(&mdev->ap_bio_cnt));
+}
+
+void drbd_resume_io(struct drbd_conf *mdev)
+{
+	clear_bit(SUSPEND_IO, &mdev->flags);
+	wake_up(&mdev->misc_wait);
+}
+
+/**
+ * drbd_determine_dev_size() -  Sets the right device size obeying all constraints
+ * @mdev:	DRBD device.
+ *
+ * Returns 0 on success, negative return values indicate errors.
+ * You should call drbd_md_sync() after calling this function.
+ */
+enum determine_dev_size drbd_determin_dev_size(struct drbd_conf *mdev) __must_hold(local)
+{
+	sector_t prev_first_sect, prev_size; /* previous meta location */
+	sector_t la_size;
+	sector_t size;
+	char ppb[10];
+
+	int md_moved, la_size_changed;
+	enum determine_dev_size rv = unchanged;
+
+	/* race:
+	 * application request passes inc_ap_bio,
+	 * but then cannot get an AL-reference.
+	 * this function later may wait on ap_bio_cnt == 0. -> deadlock.
+	 *
+	 * to avoid that:
+	 * Suspend IO right here.
+	 * still lock the act_log to not trigger ASSERTs there.
+	 */
+	drbd_suspend_io(mdev);
+
+	/* no wait necessary anymore, actually we could assert that */
+	wait_event(mdev->al_wait, lc_try_lock(mdev->act_log));
+
+	prev_first_sect = drbd_md_first_sector(mdev->ldev);
+	prev_size = mdev->ldev->md.md_size_sect;
+	la_size = mdev->ldev->md.la_size_sect;
+
+	/* TODO: should only be some assert here, not (re)init... */
+	drbd_md_set_sector_offsets(mdev, mdev->ldev);
+
+	size = drbd_new_dev_size(mdev, mdev->ldev);
+
+	if (drbd_get_capacity(mdev->this_bdev) != size ||
+	    drbd_bm_capacity(mdev) != size) {
+		int err;
+		err = drbd_bm_resize(mdev, size);
+		if (unlikely(err)) {
+			/* currently there is only one error: ENOMEM! */
+			size = drbd_bm_capacity(mdev)>>1;
+			if (size == 0) {
+				dev_err(DEV, "OUT OF MEMORY! "
+				    "Could not allocate bitmap!\n");
+			} else {
+				dev_err(DEV, "BM resizing failed. "
+				    "Leaving size unchanged at size = %lu KB\n",
+				    (unsigned long)size);
+			}
+			rv = dev_size_error;
+		}
+		/* racy, see comments above. */
+		drbd_set_my_capacity(mdev, size);
+		mdev->ldev->md.la_size_sect = size;
+		dev_info(DEV, "size = %s (%llu KB)\n", ppsize(ppb, size>>1),
+		     (unsigned long long)size>>1);
+	}
+	if (rv == dev_size_error)
+		goto out;
+
+	la_size_changed = (la_size != mdev->ldev->md.la_size_sect);
+
+	md_moved = prev_first_sect != drbd_md_first_sector(mdev->ldev)
+		|| prev_size	   != mdev->ldev->md.md_size_sect;
+
+	if (la_size_changed || md_moved) {
+		drbd_al_shrink(mdev); /* All extents inactive. */
+		dev_info(DEV, "Writing the whole bitmap, %s\n",
+			 la_size_changed && md_moved ? "size changed and md moved" :
+			 la_size_changed ? "size changed" : "md moved");
+		rv = drbd_bitmap_io(mdev, &drbd_bm_write, "size changed"); /* does drbd_resume_io() ! */
+		drbd_md_mark_dirty(mdev);
+	}
+
+	if (size > la_size)
+		rv = grew;
+	if (size < la_size)
+		rv = shrunk;
+out:
+	lc_unlock(mdev->act_log);
+	wake_up(&mdev->al_wait);
+	drbd_resume_io(mdev);
+
+	return rv;
+}
+
+sector_t
+drbd_new_dev_size(struct drbd_conf *mdev, struct drbd_backing_dev *bdev)
+{
+	sector_t p_size = mdev->p_size;   /* partner's disk size. */
+	sector_t la_size = bdev->md.la_size_sect; /* last agreed size. */
+	sector_t m_size; /* my size */
+	sector_t u_size = bdev->dc.disk_size; /* size requested by user. */
+	sector_t size = 0;
+
+	m_size = drbd_get_max_capacity(bdev);
+
+	if (p_size && m_size) {
+		size = min_t(sector_t, p_size, m_size);
+	} else {
+		if (la_size) {
+			size = la_size;
+			if (m_size && m_size < size)
+				size = m_size;
+			if (p_size && p_size < size)
+				size = p_size;
+		} else {
+			if (m_size)
+				size = m_size;
+			if (p_size)
+				size = p_size;
+		}
+	}
+
+	if (size == 0)
+		dev_err(DEV, "Both nodes diskless!\n");
+
+	if (u_size) {
+		if (u_size > size)
+			dev_err(DEV, "Requested disk size is too big (%lu > %lu)\n",
+			    (unsigned long)u_size>>1, (unsigned long)size>>1);
+		else
+			size = u_size;
+	}
+
+	return size;
+}
+
+/**
+ * drbd_check_al_size() - Ensures that the AL is of the right size
+ * @mdev:	DRBD device.
+ *
+ * Returns -EBUSY if current al lru is still used, -ENOMEM when allocation
+ * failed, and 0 on success. You should call drbd_md_sync() after you called
+ * this function.
+ */
+static int drbd_check_al_size(struct drbd_conf *mdev)
+{
+	struct lru_cache *n, *t;
+	struct lc_element *e;
+	unsigned int in_use;
+	int i;
+
+	ERR_IF(mdev->sync_conf.al_extents < 7)
+		mdev->sync_conf.al_extents = 127;
+
+	if (mdev->act_log &&
+	    mdev->act_log->nr_elements == mdev->sync_conf.al_extents)
+		return 0;
+
+	in_use = 0;
+	t = mdev->act_log;
+	n = lc_create("act_log", drbd_al_ext_cache,
+		mdev->sync_conf.al_extents, sizeof(struct lc_element), 0);
+
+	if (n == NULL) {
+		dev_err(DEV, "Cannot allocate act_log lru!\n");
+		return -ENOMEM;
+	}
+	spin_lock_irq(&mdev->al_lock);
+	if (t) {
+		for (i = 0; i < t->nr_elements; i++) {
+			e = lc_element_by_index(t, i);
+			if (e->refcnt)
+				dev_err(DEV, "refcnt(%d)==%d\n",
+				    e->lc_number, e->refcnt);
+			in_use += e->refcnt;
+		}
+	}
+	if (!in_use)
+		mdev->act_log = n;
+	spin_unlock_irq(&mdev->al_lock);
+	if (in_use) {
+		dev_err(DEV, "Activity log still in use!\n");
+		lc_destroy(n);
+		return -EBUSY;
+	} else {
+		if (t)
+			lc_destroy(t);
+	}
+	drbd_md_mark_dirty(mdev); /* we changed mdev->act_log->nr_elemens */
+	return 0;
+}
+
+void drbd_setup_queue_param(struct drbd_conf *mdev, unsigned int max_seg_s) __must_hold(local)
+{
+	struct request_queue * const q = mdev->rq_queue;
+	struct request_queue * const b = mdev->ldev->backing_bdev->bd_disk->queue;
+	int max_segments = mdev->ldev->dc.max_bio_bvecs;
+
+	if (b->merge_bvec_fn && !mdev->ldev->dc.use_bmbv)
+		max_seg_s = PAGE_SIZE;
+
+	max_seg_s = min(queue_max_sectors(b) * queue_logical_block_size(b), max_seg_s);
+
+	blk_queue_max_sectors(q, max_seg_s >> 9);
+	blk_queue_max_phys_segments(q, max_segments ? max_segments : MAX_PHYS_SEGMENTS);
+	blk_queue_max_hw_segments(q, max_segments ? max_segments : MAX_HW_SEGMENTS);
+	blk_queue_max_segment_size(q, max_seg_s);
+	blk_queue_logical_block_size(q, 512);
+	blk_queue_segment_boundary(q, PAGE_SIZE-1);
+	blk_stack_limits(&q->limits, &b->limits, 0);
+
+	if (b->merge_bvec_fn)
+		dev_warn(DEV, "Backing device's merge_bvec_fn() = %p\n",
+		     b->merge_bvec_fn);
+	dev_info(DEV, "max_segment_size ( = BIO size ) = %u\n", queue_max_segment_size(q));
+
+	if (q->backing_dev_info.ra_pages != b->backing_dev_info.ra_pages) {
+		dev_info(DEV, "Adjusting my ra_pages to backing device's (%lu -> %lu)\n",
+		     q->backing_dev_info.ra_pages,
+		     b->backing_dev_info.ra_pages);
+		q->backing_dev_info.ra_pages = b->backing_dev_info.ra_pages;
+	}
+}
+
+/* serialize deconfig (worker exiting, doing cleanup)
+ * and reconfig (drbdsetup disk, drbdsetup net)
+ *
+ * wait for a potentially exiting worker, then restart it,
+ * or start a new one.
+ */
+static void drbd_reconfig_start(struct drbd_conf *mdev)
+{
+	wait_event(mdev->state_wait, test_and_set_bit(CONFIG_PENDING, &mdev->flags));
+	wait_event(mdev->state_wait, !test_bit(DEVICE_DYING, &mdev->flags));
+	drbd_thread_start(&mdev->worker);
+}
+
+/* if still unconfigured, stops worker again.
+ * if configured now, clears CONFIG_PENDING.
+ * wakes potential waiters */
+static void drbd_reconfig_done(struct drbd_conf *mdev)
+{
+	spin_lock_irq(&mdev->req_lock);
+	if (mdev->state.disk == D_DISKLESS &&
+	    mdev->state.conn == C_STANDALONE &&
+	    mdev->state.role == R_SECONDARY) {
+		set_bit(DEVICE_DYING, &mdev->flags);
+		drbd_thread_stop_nowait(&mdev->worker);
+	} else
+		clear_bit(CONFIG_PENDING, &mdev->flags);
+	spin_unlock_irq(&mdev->req_lock);
+	wake_up(&mdev->state_wait);
+}
+
+/* does always return 0;
+ * interesting return code is in reply->ret_code */
+static int drbd_nl_disk_conf(struct drbd_conf *mdev, struct drbd_nl_cfg_req *nlp,
+			     struct drbd_nl_cfg_reply *reply)
+{
+	enum drbd_ret_codes retcode;
+	enum determine_dev_size dd;
+	sector_t max_possible_sectors;
+	sector_t min_md_device_sectors;
+	struct drbd_backing_dev *nbc = NULL; /* new_backing_conf */
+	struct inode *inode, *inode2;
+	struct lru_cache *resync_lru = NULL;
+	union drbd_state ns, os;
+	int rv;
+	int cp_discovered = 0;
+	int logical_block_size;
+
+	drbd_reconfig_start(mdev);
+
+	/* if you want to reconfigure, please tear down first */
+	if (mdev->state.disk > D_DISKLESS) {
+		retcode = ERR_DISK_CONFIGURED;
+		goto fail;
+	}
+
+	/* allocation not in the IO path, cqueue thread context */
+	nbc = kzalloc(sizeof(struct drbd_backing_dev), GFP_KERNEL);
+	if (!nbc) {
+		retcode = ERR_NOMEM;
+		goto fail;
+	}
+
+	nbc->dc.disk_size     = DRBD_DISK_SIZE_SECT_DEF;
+	nbc->dc.on_io_error   = DRBD_ON_IO_ERROR_DEF;
+	nbc->dc.fencing       = DRBD_FENCING_DEF;
+	nbc->dc.max_bio_bvecs = DRBD_MAX_BIO_BVECS_DEF;
+
+	if (!disk_conf_from_tags(mdev, nlp->tag_list, &nbc->dc)) {
+		retcode = ERR_MANDATORY_TAG;
+		goto fail;
+	}
+
+	if (nbc->dc.meta_dev_idx < DRBD_MD_INDEX_FLEX_INT) {
+		retcode = ERR_MD_IDX_INVALID;
+		goto fail;
+	}
+
+	nbc->lo_file = filp_open(nbc->dc.backing_dev, O_RDWR, 0);
+	if (IS_ERR(nbc->lo_file)) {
+		dev_err(DEV, "open(\"%s\") failed with %ld\n", nbc->dc.backing_dev,
+		    PTR_ERR(nbc->lo_file));
+		nbc->lo_file = NULL;
+		retcode = ERR_OPEN_DISK;
+		goto fail;
+	}
+
+	inode = nbc->lo_file->f_dentry->d_inode;
+
+	if (!S_ISBLK(inode->i_mode)) {
+		retcode = ERR_DISK_NOT_BDEV;
+		goto fail;
+	}
+
+	nbc->md_file = filp_open(nbc->dc.meta_dev, O_RDWR, 0);
+	if (IS_ERR(nbc->md_file)) {
+		dev_err(DEV, "open(\"%s\") failed with %ld\n", nbc->dc.meta_dev,
+		    PTR_ERR(nbc->md_file));
+		nbc->md_file = NULL;
+		retcode = ERR_OPEN_MD_DISK;
+		goto fail;
+	}
+
+	inode2 = nbc->md_file->f_dentry->d_inode;
+
+	if (!S_ISBLK(inode2->i_mode)) {
+		retcode = ERR_MD_NOT_BDEV;
+		goto fail;
+	}
+
+	nbc->backing_bdev = inode->i_bdev;
+	if (bd_claim(nbc->backing_bdev, mdev)) {
+		printk(KERN_ERR "drbd: bd_claim(%p,%p); failed [%p;%p;%u]\n",
+		       nbc->backing_bdev, mdev,
+		       nbc->backing_bdev->bd_holder,
+		       nbc->backing_bdev->bd_contains->bd_holder,
+		       nbc->backing_bdev->bd_holders);
+		retcode = ERR_BDCLAIM_DISK;
+		goto fail;
+	}
+
+	resync_lru = lc_create("resync", drbd_bm_ext_cache,
+			61, sizeof(struct bm_extent),
+			offsetof(struct bm_extent, lce));
+	if (!resync_lru) {
+		retcode = ERR_NOMEM;
+		goto release_bdev_fail;
+	}
+
+	/* meta_dev_idx >= 0: external fixed size,
+	 * possibly multiple drbd sharing one meta device.
+	 * TODO in that case, paranoia check that [md_bdev, meta_dev_idx] is
+	 * not yet used by some other drbd minor!
+	 * (if you use drbd.conf + drbdadm,
+	 * that should check it for you already; but if you don't, or someone
+	 * fooled it, we need to double check here) */
+	nbc->md_bdev = inode2->i_bdev;
+	if (bd_claim(nbc->md_bdev, (nbc->dc.meta_dev_idx < 0) ? (void *)mdev
+				: (void *) drbd_m_holder)) {
+		retcode = ERR_BDCLAIM_MD_DISK;
+		goto release_bdev_fail;
+	}
+
+	if ((nbc->backing_bdev == nbc->md_bdev) !=
+	    (nbc->dc.meta_dev_idx == DRBD_MD_INDEX_INTERNAL ||
+	     nbc->dc.meta_dev_idx == DRBD_MD_INDEX_FLEX_INT)) {
+		retcode = ERR_MD_IDX_INVALID;
+		goto release_bdev2_fail;
+	}
+
+	/* RT - for drbd_get_max_capacity() DRBD_MD_INDEX_FLEX_INT */
+	drbd_md_set_sector_offsets(mdev, nbc);
+
+	if (drbd_get_max_capacity(nbc) < nbc->dc.disk_size) {
+		dev_err(DEV, "max capacity %llu smaller than disk size %llu\n",
+			(unsigned long long) drbd_get_max_capacity(nbc),
+			(unsigned long long) nbc->dc.disk_size);
+		retcode = ERR_DISK_TO_SMALL;
+		goto release_bdev2_fail;
+	}
+
+	if (nbc->dc.meta_dev_idx < 0) {
+		max_possible_sectors = DRBD_MAX_SECTORS_FLEX;
+		/* at least one MB, otherwise it does not make sense */
+		min_md_device_sectors = (2<<10);
+	} else {
+		max_possible_sectors = DRBD_MAX_SECTORS;
+		min_md_device_sectors = MD_RESERVED_SECT * (nbc->dc.meta_dev_idx + 1);
+	}
+
+	if (drbd_get_capacity(nbc->md_bdev) > max_possible_sectors)
+		dev_warn(DEV, "truncating very big lower level device "
+		     "to currently maximum possible %llu sectors\n",
+		     (unsigned long long) max_possible_sectors);
+
+	if (drbd_get_capacity(nbc->md_bdev) < min_md_device_sectors) {
+		retcode = ERR_MD_DISK_TO_SMALL;
+		dev_warn(DEV, "refusing attach: md-device too small, "
+		     "at least %llu sectors needed for this meta-disk type\n",
+		     (unsigned long long) min_md_device_sectors);
+		goto release_bdev2_fail;
+	}
+
+	/* Make sure the new disk is big enough
+	 * (we may currently be R_PRIMARY with no local disk...) */
+	if (drbd_get_max_capacity(nbc) <
+	    drbd_get_capacity(mdev->this_bdev)) {
+		retcode = ERR_DISK_TO_SMALL;
+		goto release_bdev2_fail;
+	}
+
+	nbc->known_size = drbd_get_capacity(nbc->backing_bdev);
+
+	drbd_suspend_io(mdev);
+	/* also wait for the last barrier ack. */
+	wait_event(mdev->misc_wait, !atomic_read(&mdev->ap_pending_cnt));
+	/* and for any other previously queued work */
+	drbd_flush_workqueue(mdev);
+
+	retcode = _drbd_request_state(mdev, NS(disk, D_ATTACHING), CS_VERBOSE);
+	drbd_resume_io(mdev);
+	if (retcode < SS_SUCCESS)
+		goto release_bdev2_fail;
+
+	if (!get_ldev_if_state(mdev, D_ATTACHING))
+		goto force_diskless;
+
+	drbd_md_set_sector_offsets(mdev, nbc);
+
+	if (!mdev->bitmap) {
+		if (drbd_bm_init(mdev)) {
+			retcode = ERR_NOMEM;
+			goto force_diskless_dec;
+		}
+	}
+
+	retcode = drbd_md_read(mdev, nbc);
+	if (retcode != NO_ERROR)
+		goto force_diskless_dec;
+
+	if (mdev->state.conn < C_CONNECTED &&
+	    mdev->state.role == R_PRIMARY &&
+	    (mdev->ed_uuid & ~((u64)1)) != (nbc->md.uuid[UI_CURRENT] & ~((u64)1))) {
+		dev_err(DEV, "Can only attach to data with current UUID=%016llX\n",
+		    (unsigned long long)mdev->ed_uuid);
+		retcode = ERR_DATA_NOT_CURRENT;
+		goto force_diskless_dec;
+	}
+
+	/* Since we are diskless, fix the activity log first... */
+	if (drbd_check_al_size(mdev)) {
+		retcode = ERR_NOMEM;
+		goto force_diskless_dec;
+	}
+
+	/* Prevent shrinking of consistent devices ! */
+	if (drbd_md_test_flag(nbc, MDF_CONSISTENT) &&
+	   drbd_new_dev_size(mdev, nbc) < nbc->md.la_size_sect) {
+		dev_warn(DEV, "refusing to truncate a consistent device\n");
+		retcode = ERR_DISK_TO_SMALL;
+		goto force_diskless_dec;
+	}
+
+	if (!drbd_al_read_log(mdev, nbc)) {
+		retcode = ERR_IO_MD_DISK;
+		goto force_diskless_dec;
+	}
+
+	/* allocate a second IO page if logical_block_size != 512 */
+	logical_block_size = bdev_logical_block_size(nbc->md_bdev);
+	if (logical_block_size == 0)
+		logical_block_size = MD_SECTOR_SIZE;
+
+	if (logical_block_size != MD_SECTOR_SIZE) {
+		if (!mdev->md_io_tmpp) {
+			struct page *page = alloc_page(GFP_NOIO);
+			if (!page)
+				goto force_diskless_dec;
+
+			dev_warn(DEV, "Meta data's bdev logical_block_size = %d != %d\n",
+			     logical_block_size, MD_SECTOR_SIZE);
+			dev_warn(DEV, "Workaround engaged (has performance impact).\n");
+
+			mdev->md_io_tmpp = page;
+		}
+	}
+
+	/* Reset the "barriers don't work" bits here, then force meta data to
+	 * be written, to ensure we determine if barriers are supported. */
+	if (nbc->dc.no_md_flush)
+		set_bit(MD_NO_BARRIER, &mdev->flags);
+	else
+		clear_bit(MD_NO_BARRIER, &mdev->flags);
+
+	/* Point of no return reached.
+	 * Devices and memory are no longer released by error cleanup below.
+	 * now mdev takes over responsibility, and the state engine should
+	 * clean it up somewhere.  */
+	D_ASSERT(mdev->ldev == NULL);
+	mdev->ldev = nbc;
+	mdev->resync = resync_lru;
+	nbc = NULL;
+	resync_lru = NULL;
+
+	mdev->write_ordering = WO_bio_barrier;
+	drbd_bump_write_ordering(mdev, WO_bio_barrier);
+
+	if (drbd_md_test_flag(mdev->ldev, MDF_CRASHED_PRIMARY))
+		set_bit(CRASHED_PRIMARY, &mdev->flags);
+	else
+		clear_bit(CRASHED_PRIMARY, &mdev->flags);
+
+	if (drbd_md_test_flag(mdev->ldev, MDF_PRIMARY_IND)) {
+		set_bit(CRASHED_PRIMARY, &mdev->flags);
+		cp_discovered = 1;
+	}
+
+	mdev->send_cnt = 0;
+	mdev->recv_cnt = 0;
+	mdev->read_cnt = 0;
+	mdev->writ_cnt = 0;
+
+	drbd_setup_queue_param(mdev, DRBD_MAX_SEGMENT_SIZE);
+
+	/* If I am currently not R_PRIMARY,
+	 * but meta data primary indicator is set,
+	 * I just now recover from a hard crash,
+	 * and have been R_PRIMARY before that crash.
+	 *
+	 * Now, if I had no connection before that crash
+	 * (have been degraded R_PRIMARY), chances are that
+	 * I won't find my peer now either.
+	 *
+	 * In that case, and _only_ in that case,
+	 * we use the degr-wfc-timeout instead of the default,
+	 * so we can automatically recover from a crash of a
+	 * degraded but active "cluster" after a certain timeout.
+	 */
+	clear_bit(USE_DEGR_WFC_T, &mdev->flags);
+	if (mdev->state.role != R_PRIMARY &&
+	     drbd_md_test_flag(mdev->ldev, MDF_PRIMARY_IND) &&
+	    !drbd_md_test_flag(mdev->ldev, MDF_CONNECTED_IND))
+		set_bit(USE_DEGR_WFC_T, &mdev->flags);
+
+	dd = drbd_determin_dev_size(mdev);
+	if (dd == dev_size_error) {
+		retcode = ERR_NOMEM_BITMAP;
+		goto force_diskless_dec;
+	} else if (dd == grew)
+		set_bit(RESYNC_AFTER_NEG, &mdev->flags);
+
+	if (drbd_md_test_flag(mdev->ldev, MDF_FULL_SYNC)) {
+		dev_info(DEV, "Assuming that all blocks are out of sync "
+		     "(aka FullSync)\n");
+		if (drbd_bitmap_io(mdev, &drbd_bmio_set_n_write, "set_n_write from attaching")) {
+			retcode = ERR_IO_MD_DISK;
+			goto force_diskless_dec;
+		}
+	} else {
+		if (drbd_bitmap_io(mdev, &drbd_bm_read, "read from attaching") < 0) {
+			retcode = ERR_IO_MD_DISK;
+			goto force_diskless_dec;
+		}
+	}
+
+	if (cp_discovered) {
+		drbd_al_apply_to_bm(mdev);
+		drbd_al_to_on_disk_bm(mdev);
+	}
+
+	spin_lock_irq(&mdev->req_lock);
+	os = mdev->state;
+	ns.i = os.i;
+	/* If MDF_CONSISTENT is not set go into inconsistent state,
+	   otherwise investigate MDF_WasUpToDate...
+	   If MDF_WAS_UP_TO_DATE is not set go into D_OUTDATED disk state,
+	   otherwise into D_CONSISTENT state.
+	*/
+	if (drbd_md_test_flag(mdev->ldev, MDF_CONSISTENT)) {
+		if (drbd_md_test_flag(mdev->ldev, MDF_WAS_UP_TO_DATE))
+			ns.disk = D_CONSISTENT;
+		else
+			ns.disk = D_OUTDATED;
+	} else {
+		ns.disk = D_INCONSISTENT;
+	}
+
+	if (drbd_md_test_flag(mdev->ldev, MDF_PEER_OUT_DATED))
+		ns.pdsk = D_OUTDATED;
+
+	if ( ns.disk == D_CONSISTENT &&
+	    (ns.pdsk == D_OUTDATED || mdev->ldev->dc.fencing == FP_DONT_CARE))
+		ns.disk = D_UP_TO_DATE;
+
+	/* All tests on MDF_PRIMARY_IND, MDF_CONNECTED_IND,
+	   MDF_CONSISTENT and MDF_WAS_UP_TO_DATE must happen before
+	   this point, because drbd_request_state() modifies these
+	   flags. */
+
+	/* In case we are C_CONNECTED postpone any decision on the new disk
+	   state after the negotiation phase. */
+	if (mdev->state.conn == C_CONNECTED) {
+		mdev->new_state_tmp.i = ns.i;
+		ns.i = os.i;
+		ns.disk = D_NEGOTIATING;
+	}
+
+	rv = _drbd_set_state(mdev, ns, CS_VERBOSE, NULL);
+	ns = mdev->state;
+	spin_unlock_irq(&mdev->req_lock);
+
+	if (rv < SS_SUCCESS)
+		goto force_diskless_dec;
+
+	if (mdev->state.role == R_PRIMARY)
+		mdev->ldev->md.uuid[UI_CURRENT] |=  (u64)1;
+	else
+		mdev->ldev->md.uuid[UI_CURRENT] &= ~(u64)1;
+
+	drbd_md_mark_dirty(mdev);
+	drbd_md_sync(mdev);
+
+	kobject_uevent(&disk_to_dev(mdev->vdisk)->kobj, KOBJ_CHANGE);
+	put_ldev(mdev);
+	reply->ret_code = retcode;
+	drbd_reconfig_done(mdev);
+	return 0;
+
+ force_diskless_dec:
+	put_ldev(mdev);
+ force_diskless:
+	drbd_force_state(mdev, NS(disk, D_DISKLESS));
+	drbd_md_sync(mdev);
+ release_bdev2_fail:
+	if (nbc)
+		bd_release(nbc->md_bdev);
+ release_bdev_fail:
+	if (nbc)
+		bd_release(nbc->backing_bdev);
+ fail:
+	if (nbc) {
+		if (nbc->lo_file)
+			fput(nbc->lo_file);
+		if (nbc->md_file)
+			fput(nbc->md_file);
+		kfree(nbc);
+	}
+	lc_destroy(resync_lru);
+
+	reply->ret_code = retcode;
+	drbd_reconfig_done(mdev);
+	return 0;
+}
+
+static int drbd_nl_detach(struct drbd_conf *mdev, struct drbd_nl_cfg_req *nlp,
+			  struct drbd_nl_cfg_reply *reply)
+{
+	reply->ret_code = drbd_request_state(mdev, NS(disk, D_DISKLESS));
+	return 0;
+}
+
+static int drbd_nl_net_conf(struct drbd_conf *mdev, struct drbd_nl_cfg_req *nlp,
+			    struct drbd_nl_cfg_reply *reply)
+{
+	int i, ns;
+	enum drbd_ret_codes retcode;
+	struct net_conf *new_conf = NULL;
+	struct crypto_hash *tfm = NULL;
+	struct crypto_hash *integrity_w_tfm = NULL;
+	struct crypto_hash *integrity_r_tfm = NULL;
+	struct hlist_head *new_tl_hash = NULL;
+	struct hlist_head *new_ee_hash = NULL;
+	struct drbd_conf *odev;
+	char hmac_name[CRYPTO_MAX_ALG_NAME];
+	void *int_dig_out = NULL;
+	void *int_dig_in = NULL;
+	void *int_dig_vv = NULL;
+	struct sockaddr *new_my_addr, *new_peer_addr, *taken_addr;
+
+	drbd_reconfig_start(mdev);
+
+	if (mdev->state.conn > C_STANDALONE) {
+		retcode = ERR_NET_CONFIGURED;
+		goto fail;
+	}
+
+	/* allocation not in the IO path, cqueue thread context */
+	new_conf = kmalloc(sizeof(struct net_conf), GFP_KERNEL);
+	if (!new_conf) {
+		retcode = ERR_NOMEM;
+		goto fail;
+	}
+
+	memset(new_conf, 0, sizeof(struct net_conf));
+	new_conf->timeout	   = DRBD_TIMEOUT_DEF;
+	new_conf->try_connect_int  = DRBD_CONNECT_INT_DEF;
+	new_conf->ping_int	   = DRBD_PING_INT_DEF;
+	new_conf->max_epoch_size   = DRBD_MAX_EPOCH_SIZE_DEF;
+	new_conf->max_buffers	   = DRBD_MAX_BUFFERS_DEF;
+	new_conf->unplug_watermark = DRBD_UNPLUG_WATERMARK_DEF;
+	new_conf->sndbuf_size	   = DRBD_SNDBUF_SIZE_DEF;
+	new_conf->rcvbuf_size	   = DRBD_RCVBUF_SIZE_DEF;
+	new_conf->ko_count	   = DRBD_KO_COUNT_DEF;
+	new_conf->after_sb_0p	   = DRBD_AFTER_SB_0P_DEF;
+	new_conf->after_sb_1p	   = DRBD_AFTER_SB_1P_DEF;
+	new_conf->after_sb_2p	   = DRBD_AFTER_SB_2P_DEF;
+	new_conf->want_lose	   = 0;
+	new_conf->two_primaries    = 0;
+	new_conf->wire_protocol    = DRBD_PROT_C;
+	new_conf->ping_timeo	   = DRBD_PING_TIMEO_DEF;
+	new_conf->rr_conflict	   = DRBD_RR_CONFLICT_DEF;
+
+	if (!net_conf_from_tags(mdev, nlp->tag_list, new_conf)) {
+		retcode = ERR_MANDATORY_TAG;
+		goto fail;
+	}
+
+	if (new_conf->two_primaries
+	    && (new_conf->wire_protocol != DRBD_PROT_C)) {
+		retcode = ERR_NOT_PROTO_C;
+		goto fail;
+	};
+
+	if (mdev->state.role == R_PRIMARY && new_conf->want_lose) {
+		retcode = ERR_DISCARD;
+		goto fail;
+	}
+
+	retcode = NO_ERROR;
+
+	new_my_addr = (struct sockaddr *)&new_conf->my_addr;
+	new_peer_addr = (struct sockaddr *)&new_conf->peer_addr;
+	for (i = 0; i < minor_count; i++) {
+		odev = minor_to_mdev(i);
+		if (!odev || odev == mdev)
+			continue;
+		if (get_net_conf(odev)) {
+			taken_addr = (struct sockaddr *)&odev->net_conf->my_addr;
+			if (new_conf->my_addr_len == odev->net_conf->my_addr_len &&
+			    !memcmp(new_my_addr, taken_addr, new_conf->my_addr_len))
+				retcode = ERR_LOCAL_ADDR;
+
+			taken_addr = (struct sockaddr *)&odev->net_conf->peer_addr;
+			if (new_conf->peer_addr_len == odev->net_conf->peer_addr_len &&
+			    !memcmp(new_peer_addr, taken_addr, new_conf->peer_addr_len))
+				retcode = ERR_PEER_ADDR;
+
+			put_net_conf(odev);
+			if (retcode != NO_ERROR)
+				goto fail;
+		}
+	}
+
+	if (new_conf->cram_hmac_alg[0] != 0) {
+		snprintf(hmac_name, CRYPTO_MAX_ALG_NAME, "hmac(%s)",
+			new_conf->cram_hmac_alg);
+		tfm = crypto_alloc_hash(hmac_name, 0, CRYPTO_ALG_ASYNC);
+		if (IS_ERR(tfm)) {
+			tfm = NULL;
+			retcode = ERR_AUTH_ALG;
+			goto fail;
+		}
+
+		if (crypto_tfm_alg_type(crypto_hash_tfm(tfm))
+						!= CRYPTO_ALG_TYPE_HASH) {
+			retcode = ERR_AUTH_ALG_ND;
+			goto fail;
+		}
+	}
+
+	if (new_conf->integrity_alg[0]) {
+		integrity_w_tfm = crypto_alloc_hash(new_conf->integrity_alg, 0, CRYPTO_ALG_ASYNC);
+		if (IS_ERR(integrity_w_tfm)) {
+			integrity_w_tfm = NULL;
+			retcode=ERR_INTEGRITY_ALG;
+			goto fail;
+		}
+
+		if (!drbd_crypto_is_hash(crypto_hash_tfm(integrity_w_tfm))) {
+			retcode=ERR_INTEGRITY_ALG_ND;
+			goto fail;
+		}
+
+		integrity_r_tfm = crypto_alloc_hash(new_conf->integrity_alg, 0, CRYPTO_ALG_ASYNC);
+		if (IS_ERR(integrity_r_tfm)) {
+			integrity_r_tfm = NULL;
+			retcode=ERR_INTEGRITY_ALG;
+			goto fail;
+		}
+	}
+
+	ns = new_conf->max_epoch_size/8;
+	if (mdev->tl_hash_s != ns) {
+		new_tl_hash = kzalloc(ns*sizeof(void *), GFP_KERNEL);
+		if (!new_tl_hash) {
+			retcode = ERR_NOMEM;
+			goto fail;
+		}
+	}
+
+	ns = new_conf->max_buffers/8;
+	if (new_conf->two_primaries && (mdev->ee_hash_s != ns)) {
+		new_ee_hash = kzalloc(ns*sizeof(void *), GFP_KERNEL);
+		if (!new_ee_hash) {
+			retcode = ERR_NOMEM;
+			goto fail;
+		}
+	}
+
+	((char *)new_conf->shared_secret)[SHARED_SECRET_MAX-1] = 0;
+
+	if (integrity_w_tfm) {
+		i = crypto_hash_digestsize(integrity_w_tfm);
+		int_dig_out = kmalloc(i, GFP_KERNEL);
+		if (!int_dig_out) {
+			retcode = ERR_NOMEM;
+			goto fail;
+		}
+		int_dig_in = kmalloc(i, GFP_KERNEL);
+		if (!int_dig_in) {
+			retcode = ERR_NOMEM;
+			goto fail;
+		}
+		int_dig_vv = kmalloc(i, GFP_KERNEL);
+		if (!int_dig_vv) {
+			retcode = ERR_NOMEM;
+			goto fail;
+		}
+	}
+
+	if (!mdev->bitmap) {
+		if(drbd_bm_init(mdev)) {
+			retcode = ERR_NOMEM;
+			goto fail;
+		}
+	}
+
+	spin_lock_irq(&mdev->req_lock);
+	if (mdev->net_conf != NULL) {
+		retcode = ERR_NET_CONFIGURED;
+		spin_unlock_irq(&mdev->req_lock);
+		goto fail;
+	}
+	mdev->net_conf = new_conf;
+
+	mdev->send_cnt = 0;
+	mdev->recv_cnt = 0;
+
+	if (new_tl_hash) {
+		kfree(mdev->tl_hash);
+		mdev->tl_hash_s = mdev->net_conf->max_epoch_size/8;
+		mdev->tl_hash = new_tl_hash;
+	}
+
+	if (new_ee_hash) {
+		kfree(mdev->ee_hash);
+		mdev->ee_hash_s = mdev->net_conf->max_buffers/8;
+		mdev->ee_hash = new_ee_hash;
+	}
+
+	crypto_free_hash(mdev->cram_hmac_tfm);
+	mdev->cram_hmac_tfm = tfm;
+
+	crypto_free_hash(mdev->integrity_w_tfm);
+	mdev->integrity_w_tfm = integrity_w_tfm;
+
+	crypto_free_hash(mdev->integrity_r_tfm);
+	mdev->integrity_r_tfm = integrity_r_tfm;
+
+	kfree(mdev->int_dig_out);
+	kfree(mdev->int_dig_in);
+	kfree(mdev->int_dig_vv);
+	mdev->int_dig_out=int_dig_out;
+	mdev->int_dig_in=int_dig_in;
+	mdev->int_dig_vv=int_dig_vv;
+	spin_unlock_irq(&mdev->req_lock);
+
+	retcode = _drbd_request_state(mdev, NS(conn, C_UNCONNECTED), CS_VERBOSE);
+
+	kobject_uevent(&disk_to_dev(mdev->vdisk)->kobj, KOBJ_CHANGE);
+	reply->ret_code = retcode;
+	drbd_reconfig_done(mdev);
+	return 0;
+
+fail:
+	kfree(int_dig_out);
+	kfree(int_dig_in);
+	kfree(int_dig_vv);
+	crypto_free_hash(tfm);
+	crypto_free_hash(integrity_w_tfm);
+	crypto_free_hash(integrity_r_tfm);
+	kfree(new_tl_hash);
+	kfree(new_ee_hash);
+	kfree(new_conf);
+
+	reply->ret_code = retcode;
+	drbd_reconfig_done(mdev);
+	return 0;
+}
+
+static int drbd_nl_disconnect(struct drbd_conf *mdev, struct drbd_nl_cfg_req *nlp,
+			      struct drbd_nl_cfg_reply *reply)
+{
+	int retcode;
+
+	retcode = _drbd_request_state(mdev, NS(conn, C_DISCONNECTING), CS_ORDERED);
+
+	if (retcode == SS_NOTHING_TO_DO)
+		goto done;
+	else if (retcode == SS_ALREADY_STANDALONE)
+		goto done;
+	else if (retcode == SS_PRIMARY_NOP) {
+		/* Our statche checking code wants to see the peer outdated. */
+		retcode = drbd_request_state(mdev, NS2(conn, C_DISCONNECTING,
+						      pdsk, D_OUTDATED));
+	} else if (retcode == SS_CW_FAILED_BY_PEER) {
+		/* The peer probably wants to see us outdated. */
+		retcode = _drbd_request_state(mdev, NS2(conn, C_DISCONNECTING,
+							disk, D_OUTDATED),
+					      CS_ORDERED);
+		if (retcode == SS_IS_DISKLESS || retcode == SS_LOWER_THAN_OUTDATED) {
+			drbd_force_state(mdev, NS(conn, C_DISCONNECTING));
+			retcode = SS_SUCCESS;
+		}
+	}
+
+	if (retcode < SS_SUCCESS)
+		goto fail;
+
+	if (wait_event_interruptible(mdev->state_wait,
+				     mdev->state.conn != C_DISCONNECTING)) {
+		/* Do not test for mdev->state.conn == C_STANDALONE, since
+		   someone else might connect us in the mean time! */
+		retcode = ERR_INTR;
+		goto fail;
+	}
+
+ done:
+	retcode = NO_ERROR;
+ fail:
+	drbd_md_sync(mdev);
+	reply->ret_code = retcode;
+	return 0;
+}
+
+void resync_after_online_grow(struct drbd_conf *mdev)
+{
+	int iass; /* I am sync source */
+
+	dev_info(DEV, "Resync of new storage after online grow\n");
+	if (mdev->state.role != mdev->state.peer)
+		iass = (mdev->state.role == R_PRIMARY);
+	else
+		iass = test_bit(DISCARD_CONCURRENT, &mdev->flags);
+
+	if (iass)
+		drbd_start_resync(mdev, C_SYNC_SOURCE);
+	else
+		_drbd_request_state(mdev, NS(conn, C_WF_SYNC_UUID), CS_VERBOSE + CS_SERIALIZE);
+}
+
+static int drbd_nl_resize(struct drbd_conf *mdev, struct drbd_nl_cfg_req *nlp,
+			  struct drbd_nl_cfg_reply *reply)
+{
+	struct resize rs;
+	int retcode = NO_ERROR;
+	int ldsc = 0; /* local disk size changed */
+	enum determine_dev_size dd;
+
+	memset(&rs, 0, sizeof(struct resize));
+	if (!resize_from_tags(mdev, nlp->tag_list, &rs)) {
+		retcode = ERR_MANDATORY_TAG;
+		goto fail;
+	}
+
+	if (mdev->state.conn > C_CONNECTED) {
+		retcode = ERR_RESIZE_RESYNC;
+		goto fail;
+	}
+
+	if (mdev->state.role == R_SECONDARY &&
+	    mdev->state.peer == R_SECONDARY) {
+		retcode = ERR_NO_PRIMARY;
+		goto fail;
+	}
+
+	if (!get_ldev(mdev)) {
+		retcode = ERR_NO_DISK;
+		goto fail;
+	}
+
+	if (mdev->ldev->known_size != drbd_get_capacity(mdev->ldev->backing_bdev)) {
+		mdev->ldev->known_size = drbd_get_capacity(mdev->ldev->backing_bdev);
+		ldsc = 1;
+	}
+
+	mdev->ldev->dc.disk_size = (sector_t)rs.resize_size;
+	dd = drbd_determin_dev_size(mdev);
+	drbd_md_sync(mdev);
+	put_ldev(mdev);
+	if (dd == dev_size_error) {
+		retcode = ERR_NOMEM_BITMAP;
+		goto fail;
+	}
+
+	if (mdev->state.conn == C_CONNECTED && (dd != unchanged || ldsc)) {
+		if (dd == grew)
+			set_bit(RESIZE_PENDING, &mdev->flags);
+
+		drbd_send_uuids(mdev);
+		drbd_send_sizes(mdev, 1);
+	}
+
+ fail:
+	reply->ret_code = retcode;
+	return 0;
+}
+
+static int drbd_nl_syncer_conf(struct drbd_conf *mdev, struct drbd_nl_cfg_req *nlp,
+			       struct drbd_nl_cfg_reply *reply)
+{
+	int retcode = NO_ERROR;
+	int err;
+	int ovr; /* online verify running */
+	int rsr; /* re-sync running */
+	struct crypto_hash *verify_tfm = NULL;
+	struct crypto_hash *csums_tfm = NULL;
+	struct syncer_conf sc;
+	cpumask_var_t new_cpu_mask;
+
+	if (!zalloc_cpumask_var(&new_cpu_mask, GFP_KERNEL)) {
+		retcode = ERR_NOMEM;
+		goto fail;
+	}
+
+	if (nlp->flags & DRBD_NL_SET_DEFAULTS) {
+		memset(&sc, 0, sizeof(struct syncer_conf));
+		sc.rate       = DRBD_RATE_DEF;
+		sc.after      = DRBD_AFTER_DEF;
+		sc.al_extents = DRBD_AL_EXTENTS_DEF;
+	} else
+		memcpy(&sc, &mdev->sync_conf, sizeof(struct syncer_conf));
+
+	if (!syncer_conf_from_tags(mdev, nlp->tag_list, &sc)) {
+		retcode = ERR_MANDATORY_TAG;
+		goto fail;
+	}
+
+	/* re-sync running */
+	rsr = (	mdev->state.conn == C_SYNC_SOURCE ||
+		mdev->state.conn == C_SYNC_TARGET ||
+		mdev->state.conn == C_PAUSED_SYNC_S ||
+		mdev->state.conn == C_PAUSED_SYNC_T );
+
+	if (rsr && strcmp(sc.csums_alg, mdev->sync_conf.csums_alg)) {
+		retcode = ERR_CSUMS_RESYNC_RUNNING;
+		goto fail;
+	}
+
+	if (!rsr && sc.csums_alg[0]) {
+		csums_tfm = crypto_alloc_hash(sc.csums_alg, 0, CRYPTO_ALG_ASYNC);
+		if (IS_ERR(csums_tfm)) {
+			csums_tfm = NULL;
+			retcode = ERR_CSUMS_ALG;
+			goto fail;
+		}
+
+		if (!drbd_crypto_is_hash(crypto_hash_tfm(csums_tfm))) {
+			retcode = ERR_CSUMS_ALG_ND;
+			goto fail;
+		}
+	}
+
+	/* online verify running */
+	ovr = (mdev->state.conn == C_VERIFY_S || mdev->state.conn == C_VERIFY_T);
+
+	if (ovr) {
+		if (strcmp(sc.verify_alg, mdev->sync_conf.verify_alg)) {
+			retcode = ERR_VERIFY_RUNNING;
+			goto fail;
+		}
+	}
+
+	if (!ovr && sc.verify_alg[0]) {
+		verify_tfm = crypto_alloc_hash(sc.verify_alg, 0, CRYPTO_ALG_ASYNC);
+		if (IS_ERR(verify_tfm)) {
+			verify_tfm = NULL;
+			retcode = ERR_VERIFY_ALG;
+			goto fail;
+		}
+
+		if (!drbd_crypto_is_hash(crypto_hash_tfm(verify_tfm))) {
+			retcode = ERR_VERIFY_ALG_ND;
+			goto fail;
+		}
+	}
+
+	/* silently ignore cpu mask on UP kernel */
+	if (nr_cpu_ids > 1 && sc.cpu_mask[0] != 0) {
+		err = __bitmap_parse(sc.cpu_mask, 32, 0,
+				cpumask_bits(new_cpu_mask), nr_cpu_ids);
+		if (err) {
+			dev_warn(DEV, "__bitmap_parse() failed with %d\n", err);
+			retcode = ERR_CPU_MASK_PARSE;
+			goto fail;
+		}
+	}
+
+	ERR_IF (sc.rate < 1) sc.rate = 1;
+	ERR_IF (sc.al_extents < 7) sc.al_extents = 127; /* arbitrary minimum */
+#define AL_MAX ((MD_AL_MAX_SIZE-1) * AL_EXTENTS_PT)
+	if (sc.al_extents > AL_MAX) {
+		dev_err(DEV, "sc.al_extents > %d\n", AL_MAX);
+		sc.al_extents = AL_MAX;
+	}
+#undef AL_MAX
+
+	/* most sanity checks done, try to assign the new sync-after
+	 * dependency.  need to hold the global lock in there,
+	 * to avoid a race in the dependency loop check. */
+	retcode = drbd_alter_sa(mdev, sc.after);
+	if (retcode != NO_ERROR)
+		goto fail;
+
+	/* ok, assign the rest of it as well.
+	 * lock against receive_SyncParam() */
+	spin_lock(&mdev->peer_seq_lock);
+	mdev->sync_conf = sc;
+
+	if (!rsr) {
+		crypto_free_hash(mdev->csums_tfm);
+		mdev->csums_tfm = csums_tfm;
+		csums_tfm = NULL;
+	}
+
+	if (!ovr) {
+		crypto_free_hash(mdev->verify_tfm);
+		mdev->verify_tfm = verify_tfm;
+		verify_tfm = NULL;
+	}
+	spin_unlock(&mdev->peer_seq_lock);
+
+	if (get_ldev(mdev)) {
+		wait_event(mdev->al_wait, lc_try_lock(mdev->act_log));
+		drbd_al_shrink(mdev);
+		err = drbd_check_al_size(mdev);
+		lc_unlock(mdev->act_log);
+		wake_up(&mdev->al_wait);
+
+		put_ldev(mdev);
+		drbd_md_sync(mdev);
+
+		if (err) {
+			retcode = ERR_NOMEM;
+			goto fail;
+		}
+	}
+
+	if (mdev->state.conn >= C_CONNECTED)
+		drbd_send_sync_param(mdev, &sc);
+
+	if (!cpumask_equal(mdev->cpu_mask, new_cpu_mask)) {
+		cpumask_copy(mdev->cpu_mask, new_cpu_mask);
+		drbd_calc_cpu_mask(mdev);
+		mdev->receiver.reset_cpu_mask = 1;
+		mdev->asender.reset_cpu_mask = 1;
+		mdev->worker.reset_cpu_mask = 1;
+	}
+
+	kobject_uevent(&disk_to_dev(mdev->vdisk)->kobj, KOBJ_CHANGE);
+fail:
+	free_cpumask_var(new_cpu_mask);
+	crypto_free_hash(csums_tfm);
+	crypto_free_hash(verify_tfm);
+	reply->ret_code = retcode;
+	return 0;
+}
+
+static int drbd_nl_invalidate(struct drbd_conf *mdev, struct drbd_nl_cfg_req *nlp,
+			      struct drbd_nl_cfg_reply *reply)
+{
+	int retcode;
+
+	retcode = _drbd_request_state(mdev, NS(conn, C_STARTING_SYNC_T), CS_ORDERED);
+
+	if (retcode < SS_SUCCESS && retcode != SS_NEED_CONNECTION)
+		retcode = drbd_request_state(mdev, NS(conn, C_STARTING_SYNC_T));
+
+	while (retcode == SS_NEED_CONNECTION) {
+		spin_lock_irq(&mdev->req_lock);
+		if (mdev->state.conn < C_CONNECTED)
+			retcode = _drbd_set_state(_NS(mdev, disk, D_INCONSISTENT), CS_VERBOSE, NULL);
+		spin_unlock_irq(&mdev->req_lock);
+
+		if (retcode != SS_NEED_CONNECTION)
+			break;
+
+		retcode = drbd_request_state(mdev, NS(conn, C_STARTING_SYNC_T));
+	}
+
+	reply->ret_code = retcode;
+	return 0;
+}
+
+static int drbd_nl_invalidate_peer(struct drbd_conf *mdev, struct drbd_nl_cfg_req *nlp,
+				   struct drbd_nl_cfg_reply *reply)
+{
+
+	reply->ret_code = drbd_request_state(mdev, NS(conn, C_STARTING_SYNC_S));
+
+	return 0;
+}
+
+static int drbd_nl_pause_sync(struct drbd_conf *mdev, struct drbd_nl_cfg_req *nlp,
+			      struct drbd_nl_cfg_reply *reply)
+{
+	int retcode = NO_ERROR;
+
+	if (drbd_request_state(mdev, NS(user_isp, 1)) == SS_NOTHING_TO_DO)
+		retcode = ERR_PAUSE_IS_SET;
+
+	reply->ret_code = retcode;
+	return 0;
+}
+
+static int drbd_nl_resume_sync(struct drbd_conf *mdev, struct drbd_nl_cfg_req *nlp,
+			       struct drbd_nl_cfg_reply *reply)
+{
+	int retcode = NO_ERROR;
+
+	if (drbd_request_state(mdev, NS(user_isp, 0)) == SS_NOTHING_TO_DO)
+		retcode = ERR_PAUSE_IS_CLEAR;
+
+	reply->ret_code = retcode;
+	return 0;
+}
+
+static int drbd_nl_suspend_io(struct drbd_conf *mdev, struct drbd_nl_cfg_req *nlp,
+			      struct drbd_nl_cfg_reply *reply)
+{
+	reply->ret_code = drbd_request_state(mdev, NS(susp, 1));
+
+	return 0;
+}
+
+static int drbd_nl_resume_io(struct drbd_conf *mdev, struct drbd_nl_cfg_req *nlp,
+			     struct drbd_nl_cfg_reply *reply)
+{
+	reply->ret_code = drbd_request_state(mdev, NS(susp, 0));
+	return 0;
+}
+
+static int drbd_nl_outdate(struct drbd_conf *mdev, struct drbd_nl_cfg_req *nlp,
+			   struct drbd_nl_cfg_reply *reply)
+{
+	reply->ret_code = drbd_request_state(mdev, NS(disk, D_OUTDATED));
+	return 0;
+}
+
+static int drbd_nl_get_config(struct drbd_conf *mdev, struct drbd_nl_cfg_req *nlp,
+			   struct drbd_nl_cfg_reply *reply)
+{
+	unsigned short *tl;
+
+	tl = reply->tag_list;
+
+	if (get_ldev(mdev)) {
+		tl = disk_conf_to_tags(mdev, &mdev->ldev->dc, tl);
+		put_ldev(mdev);
+	}
+
+	if (get_net_conf(mdev)) {
+		tl = net_conf_to_tags(mdev, mdev->net_conf, tl);
+		put_net_conf(mdev);
+	}
+	tl = syncer_conf_to_tags(mdev, &mdev->sync_conf, tl);
+
+	put_unaligned(TT_END, tl++); /* Close the tag list */
+
+	return (int)((char *)tl - (char *)reply->tag_list);
+}
+
+static int drbd_nl_get_state(struct drbd_conf *mdev, struct drbd_nl_cfg_req *nlp,
+			     struct drbd_nl_cfg_reply *reply)
+{
+	unsigned short *tl = reply->tag_list;
+	union drbd_state s = mdev->state;
+	unsigned long rs_left;
+	unsigned int res;
+
+	tl = get_state_to_tags(mdev, (struct get_state *)&s, tl);
+
+	/* no local ref, no bitmap, no syncer progress. */
+	if (s.conn >= C_SYNC_SOURCE && s.conn <= C_PAUSED_SYNC_T) {
+		if (get_ldev(mdev)) {
+			drbd_get_syncer_progress(mdev, &rs_left, &res);
+			tl = tl_add_int(tl, T_sync_progress, &res);
+			put_ldev(mdev);
+		}
+	}
+	put_unaligned(TT_END, tl++); /* Close the tag list */
+
+	return (int)((char *)tl - (char *)reply->tag_list);
+}
+
+static int drbd_nl_get_uuids(struct drbd_conf *mdev, struct drbd_nl_cfg_req *nlp,
+			     struct drbd_nl_cfg_reply *reply)
+{
+	unsigned short *tl;
+
+	tl = reply->tag_list;
+
+	if (get_ldev(mdev)) {
+		tl = tl_add_blob(tl, T_uuids, mdev->ldev->md.uuid, UI_SIZE*sizeof(u64));
+		tl = tl_add_int(tl, T_uuids_flags, &mdev->ldev->md.flags);
+		put_ldev(mdev);
+	}
+	put_unaligned(TT_END, tl++); /* Close the tag list */
+
+	return (int)((char *)tl - (char *)reply->tag_list);
+}
+
+/**
+ * drbd_nl_get_timeout_flag() - Used by drbdsetup to find out which timeout value to use
+ * @mdev:	DRBD device.
+ * @nlp:	Netlink/connector packet from drbdsetup
+ * @reply:	Reply packet for drbdsetup
+ */
+static int drbd_nl_get_timeout_flag(struct drbd_conf *mdev, struct drbd_nl_cfg_req *nlp,
+				    struct drbd_nl_cfg_reply *reply)
+{
+	unsigned short *tl;
+	char rv;
+
+	tl = reply->tag_list;
+
+	rv = mdev->state.pdsk == D_OUTDATED        ? UT_PEER_OUTDATED :
+	  test_bit(USE_DEGR_WFC_T, &mdev->flags) ? UT_DEGRADED : UT_DEFAULT;
+
+	tl = tl_add_blob(tl, T_use_degraded, &rv, sizeof(rv));
+	put_unaligned(TT_END, tl++); /* Close the tag list */
+
+	return (int)((char *)tl - (char *)reply->tag_list);
+}
+
+static int drbd_nl_start_ov(struct drbd_conf *mdev, struct drbd_nl_cfg_req *nlp,
+				    struct drbd_nl_cfg_reply *reply)
+{
+	/* default to resume from last known position, if possible */
+	struct start_ov args =
+		{ .start_sector = mdev->ov_start_sector };
+
+	if (!start_ov_from_tags(mdev, nlp->tag_list, &args)) {
+		reply->ret_code = ERR_MANDATORY_TAG;
+		return 0;
+	}
+	/* w_make_ov_request expects position to be aligned */
+	mdev->ov_start_sector = args.start_sector & ~BM_SECT_PER_BIT;
+	reply->ret_code = drbd_request_state(mdev,NS(conn,C_VERIFY_S));
+	return 0;
+}
+
+
+static int drbd_nl_new_c_uuid(struct drbd_conf *mdev, struct drbd_nl_cfg_req *nlp,
+			      struct drbd_nl_cfg_reply *reply)
+{
+	int retcode = NO_ERROR;
+	int skip_initial_sync = 0;
+	int err;
+
+	struct new_c_uuid args;
+
+	memset(&args, 0, sizeof(struct new_c_uuid));
+	if (!new_c_uuid_from_tags(mdev, nlp->tag_list, &args)) {
+		reply->ret_code = ERR_MANDATORY_TAG;
+		return 0;
+	}
+
+	mutex_lock(&mdev->state_mutex); /* Protects us against serialized state changes. */
+
+	if (!get_ldev(mdev)) {
+		retcode = ERR_NO_DISK;
+		goto out;
+	}
+
+	/* this is "skip initial sync", assume to be clean */
+	if (mdev->state.conn == C_CONNECTED && mdev->agreed_pro_version >= 90 &&
+	    mdev->ldev->md.uuid[UI_CURRENT] == UUID_JUST_CREATED && args.clear_bm) {
+		dev_info(DEV, "Preparing to skip initial sync\n");
+		skip_initial_sync = 1;
+	} else if (mdev->state.conn != C_STANDALONE) {
+		retcode = ERR_CONNECTED;
+		goto out_dec;
+	}
+
+	drbd_uuid_set(mdev, UI_BITMAP, 0); /* Rotate UI_BITMAP to History 1, etc... */
+	drbd_uuid_new_current(mdev); /* New current, previous to UI_BITMAP */
+
+	if (args.clear_bm) {
+		err = drbd_bitmap_io(mdev, &drbd_bmio_clear_n_write, "clear_n_write from new_c_uuid");
+		if (err) {
+			dev_err(DEV, "Writing bitmap failed with %d\n",err);
+			retcode = ERR_IO_MD_DISK;
+		}
+		if (skip_initial_sync) {
+			drbd_send_uuids_skip_initial_sync(mdev);
+			_drbd_uuid_set(mdev, UI_BITMAP, 0);
+			spin_lock_irq(&mdev->req_lock);
+			_drbd_set_state(_NS2(mdev, disk, D_UP_TO_DATE, pdsk, D_UP_TO_DATE),
+					CS_VERBOSE, NULL);
+			spin_unlock_irq(&mdev->req_lock);
+		}
+	}
+
+	drbd_md_sync(mdev);
+out_dec:
+	put_ldev(mdev);
+out:
+	mutex_unlock(&mdev->state_mutex);
+
+	reply->ret_code = retcode;
+	return 0;
+}
+
+static struct drbd_conf *ensure_mdev(struct drbd_nl_cfg_req *nlp)
+{
+	struct drbd_conf *mdev;
+
+	if (nlp->drbd_minor >= minor_count)
+		return NULL;
+
+	mdev = minor_to_mdev(nlp->drbd_minor);
+
+	if (!mdev && (nlp->flags & DRBD_NL_CREATE_DEVICE)) {
+		struct gendisk *disk = NULL;
+		mdev = drbd_new_device(nlp->drbd_minor);
+
+		spin_lock_irq(&drbd_pp_lock);
+		if (minor_table[nlp->drbd_minor] == NULL) {
+			minor_table[nlp->drbd_minor] = mdev;
+			disk = mdev->vdisk;
+			mdev = NULL;
+		} /* else: we lost the race */
+		spin_unlock_irq(&drbd_pp_lock);
+
+		if (disk) /* we won the race above */
+			/* in case we ever add a drbd_delete_device(),
+			 * don't forget the del_gendisk! */
+			add_disk(disk);
+		else /* we lost the race above */
+			drbd_free_mdev(mdev);
+
+		mdev = minor_to_mdev(nlp->drbd_minor);
+	}
+
+	return mdev;
+}
+
+struct cn_handler_struct {
+	int (*function)(struct drbd_conf *,
+			 struct drbd_nl_cfg_req *,
+			 struct drbd_nl_cfg_reply *);
+	int reply_body_size;
+};
+
+static struct cn_handler_struct cnd_table[] = {
+	[ P_primary ]		= { &drbd_nl_primary,		0 },
+	[ P_secondary ]		= { &drbd_nl_secondary,		0 },
+	[ P_disk_conf ]		= { &drbd_nl_disk_conf,		0 },
+	[ P_detach ]		= { &drbd_nl_detach,		0 },
+	[ P_net_conf ]		= { &drbd_nl_net_conf,		0 },
+	[ P_disconnect ]	= { &drbd_nl_disconnect,	0 },
+	[ P_resize ]		= { &drbd_nl_resize,		0 },
+	[ P_syncer_conf ]	= { &drbd_nl_syncer_conf,	0 },
+	[ P_invalidate ]	= { &drbd_nl_invalidate,	0 },
+	[ P_invalidate_peer ]	= { &drbd_nl_invalidate_peer,	0 },
+	[ P_pause_sync ]	= { &drbd_nl_pause_sync,	0 },
+	[ P_resume_sync ]	= { &drbd_nl_resume_sync,	0 },
+	[ P_suspend_io ]	= { &drbd_nl_suspend_io,	0 },
+	[ P_resume_io ]		= { &drbd_nl_resume_io,		0 },
+	[ P_outdate ]		= { &drbd_nl_outdate,		0 },
+	[ P_get_config ]	= { &drbd_nl_get_config,
+				    sizeof(struct syncer_conf_tag_len_struct) +
+				    sizeof(struct disk_conf_tag_len_struct) +
+				    sizeof(struct net_conf_tag_len_struct) },
+	[ P_get_state ]		= { &drbd_nl_get_state,
+				    sizeof(struct get_state_tag_len_struct) +
+				    sizeof(struct sync_progress_tag_len_struct)	},
+	[ P_get_uuids ]		= { &drbd_nl_get_uuids,
+				    sizeof(struct get_uuids_tag_len_struct) },
+	[ P_get_timeout_flag ]	= { &drbd_nl_get_timeout_flag,
+				    sizeof(struct get_timeout_flag_tag_len_struct)},
+	[ P_start_ov ]		= { &drbd_nl_start_ov,		0 },
+	[ P_new_c_uuid ]	= { &drbd_nl_new_c_uuid,	0 },
+};
+
+static void drbd_connector_callback(struct cn_msg *req)
+{
+	struct drbd_nl_cfg_req *nlp = (struct drbd_nl_cfg_req *)req->data;
+	struct cn_handler_struct *cm;
+	struct cn_msg *cn_reply;
+	struct drbd_nl_cfg_reply *reply;
+	struct drbd_conf *mdev;
+	int retcode, rr;
+	int reply_size = sizeof(struct cn_msg)
+		+ sizeof(struct drbd_nl_cfg_reply)
+		+ sizeof(short int);
+
+	if (!try_module_get(THIS_MODULE)) {
+		printk(KERN_ERR "drbd: try_module_get() failed!\n");
+		return;
+	}
+
+	mdev = ensure_mdev(nlp);
+	if (!mdev) {
+		retcode = ERR_MINOR_INVALID;
+		goto fail;
+	}
+
+	trace_drbd_netlink(req, 1);
+
+	if (nlp->packet_type >= P_nl_after_last_packet) {
+		retcode = ERR_PACKET_NR;
+		goto fail;
+	}
+
+	cm = cnd_table + nlp->packet_type;
+
+	/* This may happen if packet number is 0: */
+	if (cm->function == NULL) {
+		retcode = ERR_PACKET_NR;
+		goto fail;
+	}
+
+	reply_size += cm->reply_body_size;
+
+	/* allocation not in the IO path, cqueue thread context */
+	cn_reply = kmalloc(reply_size, GFP_KERNEL);
+	if (!cn_reply) {
+		retcode = ERR_NOMEM;
+		goto fail;
+	}
+	reply = (struct drbd_nl_cfg_reply *) cn_reply->data;
+
+	reply->packet_type =
+		cm->reply_body_size ? nlp->packet_type : P_nl_after_last_packet;
+	reply->minor = nlp->drbd_minor;
+	reply->ret_code = NO_ERROR; /* Might by modified by cm->function. */
+	/* reply->tag_list; might be modified by cm->function. */
+
+	rr = cm->function(mdev, nlp, reply);
+
+	cn_reply->id = req->id;
+	cn_reply->seq = req->seq;
+	cn_reply->ack = req->ack  + 1;
+	cn_reply->len = sizeof(struct drbd_nl_cfg_reply) + rr;
+	cn_reply->flags = 0;
+
+	trace_drbd_netlink(cn_reply, 0);
+	rr = cn_netlink_send(cn_reply, CN_IDX_DRBD, GFP_KERNEL);
+	if (rr && rr != -ESRCH)
+		printk(KERN_INFO "drbd: cn_netlink_send()=%d\n", rr);
+
+	kfree(cn_reply);
+	module_put(THIS_MODULE);
+	return;
+ fail:
+	drbd_nl_send_reply(req, retcode);
+	module_put(THIS_MODULE);
+}
+
+static atomic_t drbd_nl_seq = ATOMIC_INIT(2); /* two. */
+
+static unsigned short *
+__tl_add_blob(unsigned short *tl, enum drbd_tags tag, const void *data,
+	unsigned short len, int nul_terminated)
+{
+	unsigned short l = tag_descriptions[tag_number(tag)].max_len;
+	len = (len < l) ? len :  l;
+	put_unaligned(tag, tl++);
+	put_unaligned(len, tl++);
+	memcpy(tl, data, len);
+	tl = (unsigned short*)((char*)tl + len);
+	if (nul_terminated)
+		*((char*)tl - 1) = 0;
+	return tl;
+}
+
+static unsigned short *
+tl_add_blob(unsigned short *tl, enum drbd_tags tag, const void *data, int len)
+{
+	return __tl_add_blob(tl, tag, data, len, 0);
+}
+
+static unsigned short *
+tl_add_str(unsigned short *tl, enum drbd_tags tag, const char *str)
+{
+	return __tl_add_blob(tl, tag, str, strlen(str)+1, 0);
+}
+
+static unsigned short *
+tl_add_int(unsigned short *tl, enum drbd_tags tag, const void *val)
+{
+	put_unaligned(tag, tl++);
+	switch(tag_type(tag)) {
+	case TT_INTEGER:
+		put_unaligned(sizeof(int), tl++);
+		put_unaligned(*(int *)val, (int *)tl);
+		tl = (unsigned short*)((char*)tl+sizeof(int));
+		break;
+	case TT_INT64:
+		put_unaligned(sizeof(u64), tl++);
+		put_unaligned(*(u64 *)val, (u64 *)tl);
+		tl = (unsigned short*)((char*)tl+sizeof(u64));
+		break;
+	default:
+		/* someone did something stupid. */
+		;
+	}
+	return tl;
+}
+
+void drbd_bcast_state(struct drbd_conf *mdev, union drbd_state state)
+{
+	char buffer[sizeof(struct cn_msg)+
+		    sizeof(struct drbd_nl_cfg_reply)+
+		    sizeof(struct get_state_tag_len_struct)+
+		    sizeof(short int)];
+	struct cn_msg *cn_reply = (struct cn_msg *) buffer;
+	struct drbd_nl_cfg_reply *reply =
+		(struct drbd_nl_cfg_reply *)cn_reply->data;
+	unsigned short *tl = reply->tag_list;
+
+	/* dev_warn(DEV, "drbd_bcast_state() got called\n"); */
+
+	tl = get_state_to_tags(mdev, (struct get_state *)&state, tl);
+
+	put_unaligned(TT_END, tl++); /* Close the tag list */
+
+	cn_reply->id.idx = CN_IDX_DRBD;
+	cn_reply->id.val = CN_VAL_DRBD;
+
+	cn_reply->seq = atomic_add_return(1, &drbd_nl_seq);
+	cn_reply->ack = 0; /* not used here. */
+	cn_reply->len = sizeof(struct drbd_nl_cfg_reply) +
+		(int)((char *)tl - (char *)reply->tag_list);
+	cn_reply->flags = 0;
+
+	reply->packet_type = P_get_state;
+	reply->minor = mdev_to_minor(mdev);
+	reply->ret_code = NO_ERROR;
+
+	trace_drbd_netlink(cn_reply, 0);
+	cn_netlink_send(cn_reply, CN_IDX_DRBD, GFP_NOIO);
+}
+
+void drbd_bcast_ev_helper(struct drbd_conf *mdev, char *helper_name)
+{
+	char buffer[sizeof(struct cn_msg)+
+		    sizeof(struct drbd_nl_cfg_reply)+
+		    sizeof(struct call_helper_tag_len_struct)+
+		    sizeof(short int)];
+	struct cn_msg *cn_reply = (struct cn_msg *) buffer;
+	struct drbd_nl_cfg_reply *reply =
+		(struct drbd_nl_cfg_reply *)cn_reply->data;
+	unsigned short *tl = reply->tag_list;
+
+	/* dev_warn(DEV, "drbd_bcast_state() got called\n"); */
+
+	tl = tl_add_str(tl, T_helper, helper_name);
+	put_unaligned(TT_END, tl++); /* Close the tag list */
+
+	cn_reply->id.idx = CN_IDX_DRBD;
+	cn_reply->id.val = CN_VAL_DRBD;
+
+	cn_reply->seq = atomic_add_return(1, &drbd_nl_seq);
+	cn_reply->ack = 0; /* not used here. */
+	cn_reply->len = sizeof(struct drbd_nl_cfg_reply) +
+		(int)((char *)tl - (char *)reply->tag_list);
+	cn_reply->flags = 0;
+
+	reply->packet_type = P_call_helper;
+	reply->minor = mdev_to_minor(mdev);
+	reply->ret_code = NO_ERROR;
+
+	trace_drbd_netlink(cn_reply, 0);
+	cn_netlink_send(cn_reply, CN_IDX_DRBD, GFP_NOIO);
+}
+
+void drbd_bcast_ee(struct drbd_conf *mdev,
+		const char *reason, const int dgs,
+		const char* seen_hash, const char* calc_hash,
+		const struct drbd_epoch_entry* e)
+{
+	struct cn_msg *cn_reply;
+	struct drbd_nl_cfg_reply *reply;
+	struct bio_vec *bvec;
+	unsigned short *tl;
+	int i;
+
+	if (!e)
+		return;
+	if (!reason || !reason[0])
+		return;
+
+	/* apparently we have to memcpy twice, first to prepare the data for the
+	 * struct cn_msg, then within cn_netlink_send from the cn_msg to the
+	 * netlink skb. */
+	/* receiver thread context, which is not in the writeout path (of this node),
+	 * but may be in the writeout path of the _other_ node.
+	 * GFP_NOIO to avoid potential "distributed deadlock". */
+	cn_reply = kmalloc(
+		sizeof(struct cn_msg)+
+		sizeof(struct drbd_nl_cfg_reply)+
+		sizeof(struct dump_ee_tag_len_struct)+
+		sizeof(short int),
+		GFP_NOIO);
+
+	if (!cn_reply) {
+		dev_err(DEV, "could not kmalloc buffer for drbd_bcast_ee, sector %llu, size %u\n",
+				(unsigned long long)e->sector, e->size);
+		return;
+	}
+
+	reply = (struct drbd_nl_cfg_reply*)cn_reply->data;
+	tl = reply->tag_list;
+
+	tl = tl_add_str(tl, T_dump_ee_reason, reason);
+	tl = tl_add_blob(tl, T_seen_digest, seen_hash, dgs);
+	tl = tl_add_blob(tl, T_calc_digest, calc_hash, dgs);
+	tl = tl_add_int(tl, T_ee_sector, &e->sector);
+	tl = tl_add_int(tl, T_ee_block_id, &e->block_id);
+
+	put_unaligned(T_ee_data, tl++);
+	put_unaligned(e->size, tl++);
+
+	__bio_for_each_segment(bvec, e->private_bio, i, 0) {
+		void *d = kmap(bvec->bv_page);
+		memcpy(tl, d + bvec->bv_offset, bvec->bv_len);
+		kunmap(bvec->bv_page);
+		tl=(unsigned short*)((char*)tl + bvec->bv_len);
+	}
+	put_unaligned(TT_END, tl++); /* Close the tag list */
+
+	cn_reply->id.idx = CN_IDX_DRBD;
+	cn_reply->id.val = CN_VAL_DRBD;
+
+	cn_reply->seq = atomic_add_return(1,&drbd_nl_seq);
+	cn_reply->ack = 0; // not used here.
+	cn_reply->len = sizeof(struct drbd_nl_cfg_reply) +
+		(int)((char*)tl - (char*)reply->tag_list);
+	cn_reply->flags = 0;
+
+	reply->packet_type = P_dump_ee;
+	reply->minor = mdev_to_minor(mdev);
+	reply->ret_code = NO_ERROR;
+
+	trace_drbd_netlink(cn_reply, 0);
+	cn_netlink_send(cn_reply, CN_IDX_DRBD, GFP_NOIO);
+	kfree(cn_reply);
+}
+
+void drbd_bcast_sync_progress(struct drbd_conf *mdev)
+{
+	char buffer[sizeof(struct cn_msg)+
+		    sizeof(struct drbd_nl_cfg_reply)+
+		    sizeof(struct sync_progress_tag_len_struct)+
+		    sizeof(short int)];
+	struct cn_msg *cn_reply = (struct cn_msg *) buffer;
+	struct drbd_nl_cfg_reply *reply =
+		(struct drbd_nl_cfg_reply *)cn_reply->data;
+	unsigned short *tl = reply->tag_list;
+	unsigned long rs_left;
+	unsigned int res;
+
+	/* no local ref, no bitmap, no syncer progress, no broadcast. */
+	if (!get_ldev(mdev))
+		return;
+	drbd_get_syncer_progress(mdev, &rs_left, &res);
+	put_ldev(mdev);
+
+	tl = tl_add_int(tl, T_sync_progress, &res);
+	put_unaligned(TT_END, tl++); /* Close the tag list */
+
+	cn_reply->id.idx = CN_IDX_DRBD;
+	cn_reply->id.val = CN_VAL_DRBD;
+
+	cn_reply->seq = atomic_add_return(1, &drbd_nl_seq);
+	cn_reply->ack = 0; /* not used here. */
+	cn_reply->len = sizeof(struct drbd_nl_cfg_reply) +
+		(int)((char *)tl - (char *)reply->tag_list);
+	cn_reply->flags = 0;
+
+	reply->packet_type = P_sync_progress;
+	reply->minor = mdev_to_minor(mdev);
+	reply->ret_code = NO_ERROR;
+
+	trace_drbd_netlink(cn_reply, 0);
+	cn_netlink_send(cn_reply, CN_IDX_DRBD, GFP_NOIO);
+}
+
+int __init drbd_nl_init(void)
+{
+	static struct cb_id cn_id_drbd;
+	int err, try=10;
+
+	cn_id_drbd.val = CN_VAL_DRBD;
+	do {
+		cn_id_drbd.idx = cn_idx;
+		err = cn_add_callback(&cn_id_drbd, "cn_drbd", &drbd_connector_callback);
+		if (!err)
+			break;
+		cn_idx = (cn_idx + CN_IDX_STEP);
+	} while (try--);
+
+	if (err) {
+		printk(KERN_ERR "drbd: cn_drbd failed to register\n");
+		return err;
+	}
+
+	return 0;
+}
+
+void drbd_nl_cleanup(void)
+{
+	static struct cb_id cn_id_drbd;
+
+	cn_id_drbd.idx = cn_idx;
+	cn_id_drbd.val = CN_VAL_DRBD;
+
+	cn_del_callback(&cn_id_drbd);
+}
+
+void drbd_nl_send_reply(struct cn_msg *req, int ret_code)
+{
+	char buffer[sizeof(struct cn_msg)+sizeof(struct drbd_nl_cfg_reply)];
+	struct cn_msg *cn_reply = (struct cn_msg *) buffer;
+	struct drbd_nl_cfg_reply *reply =
+		(struct drbd_nl_cfg_reply *)cn_reply->data;
+	int rr;
+
+	cn_reply->id = req->id;
+
+	cn_reply->seq = req->seq;
+	cn_reply->ack = req->ack  + 1;
+	cn_reply->len = sizeof(struct drbd_nl_cfg_reply);
+	cn_reply->flags = 0;
+
+	reply->minor = ((struct drbd_nl_cfg_req *)req->data)->drbd_minor;
+	reply->ret_code = ret_code;
+
+	trace_drbd_netlink(cn_reply, 0);
+	rr = cn_netlink_send(cn_reply, CN_IDX_DRBD, GFP_NOIO);
+	if (rr && rr != -ESRCH)
+		printk(KERN_INFO "drbd: cn_netlink_send()=%d\n", rr);
+}
+
diff --git a/drivers/block/drbd/drbd_proc.c b/drivers/block/drbd/drbd_proc.c
new file mode 100644
index 00000000000..98fcb7450c7
--- /dev/null
+++ b/drivers/block/drbd/drbd_proc.c
@@ -0,0 +1,266 @@
+/*
+   drbd_proc.c
+
+   This file is part of DRBD by Philipp Reisner and Lars Ellenberg.
+
+   Copyright (C) 2001-2008, LINBIT Information Technologies GmbH.
+   Copyright (C) 1999-2008, Philipp Reisner <philipp.reisner@linbit.com>.
+   Copyright (C) 2002-2008, Lars Ellenberg <lars.ellenberg@linbit.com>.
+
+   drbd is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 2, or (at your option)
+   any later version.
+
+   drbd is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with drbd; see the file COPYING.  If not, write to
+   the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
+
+ */
+
+#include <linux/autoconf.h>
+#include <linux/module.h>
+
+#include <asm/uaccess.h>
+#include <linux/fs.h>
+#include <linux/file.h>
+#include <linux/slab.h>
+#include <linux/proc_fs.h>
+#include <linux/seq_file.h>
+#include <linux/drbd.h>
+#include "drbd_int.h"
+
+static int drbd_proc_open(struct inode *inode, struct file *file);
+
+
+struct proc_dir_entry *drbd_proc;
+struct file_operations drbd_proc_fops = {
+	.owner		= THIS_MODULE,
+	.open		= drbd_proc_open,
+	.read		= seq_read,
+	.llseek		= seq_lseek,
+	.release	= single_release,
+};
+
+
+/*lge
+ * progress bars shamelessly adapted from driver/md/md.c
+ * output looks like
+ *	[=====>..............] 33.5% (23456/123456)
+ *	finish: 2:20:20 speed: 6,345 (6,456) K/sec
+ */
+static void drbd_syncer_progress(struct drbd_conf *mdev, struct seq_file *seq)
+{
+	unsigned long db, dt, dbdt, rt, rs_left;
+	unsigned int res;
+	int i, x, y;
+
+	drbd_get_syncer_progress(mdev, &rs_left, &res);
+
+	x = res/50;
+	y = 20-x;
+	seq_printf(seq, "\t[");
+	for (i = 1; i < x; i++)
+		seq_printf(seq, "=");
+	seq_printf(seq, ">");
+	for (i = 0; i < y; i++)
+		seq_printf(seq, ".");
+	seq_printf(seq, "] ");
+
+	seq_printf(seq, "sync'ed:%3u.%u%% ", res / 10, res % 10);
+	/* if more than 1 GB display in MB */
+	if (mdev->rs_total > 0x100000L)
+		seq_printf(seq, "(%lu/%lu)M\n\t",
+			    (unsigned long) Bit2KB(rs_left >> 10),
+			    (unsigned long) Bit2KB(mdev->rs_total >> 10));
+	else
+		seq_printf(seq, "(%lu/%lu)K\n\t",
+			    (unsigned long) Bit2KB(rs_left),
+			    (unsigned long) Bit2KB(mdev->rs_total));
+
+	/* see drivers/md/md.c
+	 * We do not want to overflow, so the order of operands and
+	 * the * 100 / 100 trick are important. We do a +1 to be
+	 * safe against division by zero. We only estimate anyway.
+	 *
+	 * dt: time from mark until now
+	 * db: blocks written from mark until now
+	 * rt: remaining time
+	 */
+	dt = (jiffies - mdev->rs_mark_time) / HZ;
+
+	if (dt > 20) {
+		/* if we made no update to rs_mark_time for too long,
+		 * we are stalled. show that. */
+		seq_printf(seq, "stalled\n");
+		return;
+	}
+
+	if (!dt)
+		dt++;
+	db = mdev->rs_mark_left - rs_left;
+	rt = (dt * (rs_left / (db/100+1)))/100; /* seconds */
+
+	seq_printf(seq, "finish: %lu:%02lu:%02lu",
+		rt / 3600, (rt % 3600) / 60, rt % 60);
+
+	/* current speed average over (SYNC_MARKS * SYNC_MARK_STEP) jiffies */
+	dbdt = Bit2KB(db/dt);
+	if (dbdt > 1000)
+		seq_printf(seq, " speed: %ld,%03ld",
+			dbdt/1000, dbdt % 1000);
+	else
+		seq_printf(seq, " speed: %ld", dbdt);
+
+	/* mean speed since syncer started
+	 * we do account for PausedSync periods */
+	dt = (jiffies - mdev->rs_start - mdev->rs_paused) / HZ;
+	if (dt <= 0)
+		dt = 1;
+	db = mdev->rs_total - rs_left;
+	dbdt = Bit2KB(db/dt);
+	if (dbdt > 1000)
+		seq_printf(seq, " (%ld,%03ld)",
+			dbdt/1000, dbdt % 1000);
+	else
+		seq_printf(seq, " (%ld)", dbdt);
+
+	seq_printf(seq, " K/sec\n");
+}
+
+static void resync_dump_detail(struct seq_file *seq, struct lc_element *e)
+{
+	struct bm_extent *bme = lc_entry(e, struct bm_extent, lce);
+
+	seq_printf(seq, "%5d %s %s\n", bme->rs_left,
+		   bme->flags & BME_NO_WRITES ? "NO_WRITES" : "---------",
+		   bme->flags & BME_LOCKED ? "LOCKED" : "------"
+		   );
+}
+
+static int drbd_seq_show(struct seq_file *seq, void *v)
+{
+	int i, hole = 0;
+	const char *sn;
+	struct drbd_conf *mdev;
+
+	static char write_ordering_chars[] = {
+		[WO_none] = 'n',
+		[WO_drain_io] = 'd',
+		[WO_bdev_flush] = 'f',
+		[WO_bio_barrier] = 'b',
+	};
+
+	seq_printf(seq, "version: " REL_VERSION " (api:%d/proto:%d-%d)\n%s\n",
+		   API_VERSION, PRO_VERSION_MIN, PRO_VERSION_MAX, drbd_buildtag());
+
+	/*
+	  cs .. connection state
+	  ro .. node role (local/remote)
+	  ds .. disk state (local/remote)
+	     protocol
+	     various flags
+	  ns .. network send
+	  nr .. network receive
+	  dw .. disk write
+	  dr .. disk read
+	  al .. activity log write count
+	  bm .. bitmap update write count
+	  pe .. pending (waiting for ack or data reply)
+	  ua .. unack'd (still need to send ack or data reply)
+	  ap .. application requests accepted, but not yet completed
+	  ep .. number of epochs currently "on the fly", P_BARRIER_ACK pending
+	  wo .. write ordering mode currently in use
+	 oos .. known out-of-sync kB
+	*/
+
+	for (i = 0; i < minor_count; i++) {
+		mdev = minor_to_mdev(i);
+		if (!mdev) {
+			hole = 1;
+			continue;
+		}
+		if (hole) {
+			hole = 0;
+			seq_printf(seq, "\n");
+		}
+
+		sn = drbd_conn_str(mdev->state.conn);
+
+		if (mdev->state.conn == C_STANDALONE &&
+		    mdev->state.disk == D_DISKLESS &&
+		    mdev->state.role == R_SECONDARY) {
+			seq_printf(seq, "%2d: cs:Unconfigured\n", i);
+		} else {
+			seq_printf(seq,
+			   "%2d: cs:%s ro:%s/%s ds:%s/%s %c %c%c%c%c%c\n"
+			   "    ns:%u nr:%u dw:%u dr:%u al:%u bm:%u "
+			   "lo:%d pe:%d ua:%d ap:%d ep:%d wo:%c",
+			   i, sn,
+			   drbd_role_str(mdev->state.role),
+			   drbd_role_str(mdev->state.peer),
+			   drbd_disk_str(mdev->state.disk),
+			   drbd_disk_str(mdev->state.pdsk),
+			   (mdev->net_conf == NULL ? ' ' :
+			    (mdev->net_conf->wire_protocol - DRBD_PROT_A+'A')),
+			   mdev->state.susp ? 's' : 'r',
+			   mdev->state.aftr_isp ? 'a' : '-',
+			   mdev->state.peer_isp ? 'p' : '-',
+			   mdev->state.user_isp ? 'u' : '-',
+			   mdev->congestion_reason ?: '-',
+			   mdev->send_cnt/2,
+			   mdev->recv_cnt/2,
+			   mdev->writ_cnt/2,
+			   mdev->read_cnt/2,
+			   mdev->al_writ_cnt,
+			   mdev->bm_writ_cnt,
+			   atomic_read(&mdev->local_cnt),
+			   atomic_read(&mdev->ap_pending_cnt) +
+			   atomic_read(&mdev->rs_pending_cnt),
+			   atomic_read(&mdev->unacked_cnt),
+			   atomic_read(&mdev->ap_bio_cnt),
+			   mdev->epochs,
+			   write_ordering_chars[mdev->write_ordering]
+			);
+			seq_printf(seq, " oos:%lu\n",
+				   Bit2KB(drbd_bm_total_weight(mdev)));
+		}
+		if (mdev->state.conn == C_SYNC_SOURCE ||
+		    mdev->state.conn == C_SYNC_TARGET)
+			drbd_syncer_progress(mdev, seq);
+
+		if (mdev->state.conn == C_VERIFY_S || mdev->state.conn == C_VERIFY_T)
+			seq_printf(seq, "\t%3d%%      %lu/%lu\n",
+				   (int)((mdev->rs_total-mdev->ov_left) /
+					 (mdev->rs_total/100+1)),
+				   mdev->rs_total - mdev->ov_left,
+				   mdev->rs_total);
+
+		if (proc_details >= 1 && get_ldev_if_state(mdev, D_FAILED)) {
+			lc_seq_printf_stats(seq, mdev->resync);
+			lc_seq_printf_stats(seq, mdev->act_log);
+			put_ldev(mdev);
+		}
+
+		if (proc_details >= 2) {
+			if (mdev->resync) {
+				lc_seq_dump_details(seq, mdev->resync, "rs_left",
+					resync_dump_detail);
+			}
+		}
+	}
+
+	return 0;
+}
+
+static int drbd_proc_open(struct inode *inode, struct file *file)
+{
+	return single_open(file, drbd_seq_show, PDE(inode)->data);
+}
+
+/* PROC FS stuff end */
diff --git a/drivers/block/drbd/drbd_receiver.c b/drivers/block/drbd/drbd_receiver.c
new file mode 100644
index 00000000000..63686c4d85c
--- /dev/null
+++ b/drivers/block/drbd/drbd_receiver.c
@@ -0,0 +1,4456 @@
+/*
+   drbd_receiver.c
+
+   This file is part of DRBD by Philipp Reisner and Lars Ellenberg.
+
+   Copyright (C) 2001-2008, LINBIT Information Technologies GmbH.
+   Copyright (C) 1999-2008, Philipp Reisner <philipp.reisner@linbit.com>.
+   Copyright (C) 2002-2008, Lars Ellenberg <lars.ellenberg@linbit.com>.
+
+   drbd is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 2, or (at your option)
+   any later version.
+
+   drbd is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with drbd; see the file COPYING.  If not, write to
+   the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+
+#include <linux/autoconf.h>
+#include <linux/module.h>
+
+#include <asm/uaccess.h>
+#include <net/sock.h>
+
+#include <linux/version.h>
+#include <linux/drbd.h>
+#include <linux/fs.h>
+#include <linux/file.h>
+#include <linux/in.h>
+#include <linux/mm.h>
+#include <linux/memcontrol.h>
+#include <linux/mm_inline.h>
+#include <linux/slab.h>
+#include <linux/smp_lock.h>
+#include <linux/pkt_sched.h>
+#define __KERNEL_SYSCALLS__
+#include <linux/unistd.h>
+#include <linux/vmalloc.h>
+#include <linux/random.h>
+#include <linux/mm.h>
+#include <linux/string.h>
+#include <linux/scatterlist.h>
+#include "drbd_int.h"
+#include "drbd_tracing.h"
+#include "drbd_req.h"
+
+#include "drbd_vli.h"
+
+struct flush_work {
+	struct drbd_work w;
+	struct drbd_epoch *epoch;
+};
+
+enum finish_epoch {
+	FE_STILL_LIVE,
+	FE_DESTROYED,
+	FE_RECYCLED,
+};
+
+static int drbd_do_handshake(struct drbd_conf *mdev);
+static int drbd_do_auth(struct drbd_conf *mdev);
+
+static enum finish_epoch drbd_may_finish_epoch(struct drbd_conf *, struct drbd_epoch *, enum epoch_event);
+static int e_end_block(struct drbd_conf *, struct drbd_work *, int);
+
+static struct drbd_epoch *previous_epoch(struct drbd_conf *mdev, struct drbd_epoch *epoch)
+{
+	struct drbd_epoch *prev;
+	spin_lock(&mdev->epoch_lock);
+	prev = list_entry(epoch->list.prev, struct drbd_epoch, list);
+	if (prev == epoch || prev == mdev->current_epoch)
+		prev = NULL;
+	spin_unlock(&mdev->epoch_lock);
+	return prev;
+}
+
+#define GFP_TRY	(__GFP_HIGHMEM | __GFP_NOWARN)
+
+static struct page *drbd_pp_first_page_or_try_alloc(struct drbd_conf *mdev)
+{
+	struct page *page = NULL;
+
+	/* Yes, testing drbd_pp_vacant outside the lock is racy.
+	 * So what. It saves a spin_lock. */
+	if (drbd_pp_vacant > 0) {
+		spin_lock(&drbd_pp_lock);
+		page = drbd_pp_pool;
+		if (page) {
+			drbd_pp_pool = (struct page *)page_private(page);
+			set_page_private(page, 0); /* just to be polite */
+			drbd_pp_vacant--;
+		}
+		spin_unlock(&drbd_pp_lock);
+	}
+	/* GFP_TRY, because we must not cause arbitrary write-out: in a DRBD
+	 * "criss-cross" setup, that might cause write-out on some other DRBD,
+	 * which in turn might block on the other node at this very place.  */
+	if (!page)
+		page = alloc_page(GFP_TRY);
+	if (page)
+		atomic_inc(&mdev->pp_in_use);
+	return page;
+}
+
+/* kick lower level device, if we have more than (arbitrary number)
+ * reference counts on it, which typically are locally submitted io
+ * requests.  don't use unacked_cnt, so we speed up proto A and B, too. */
+static void maybe_kick_lo(struct drbd_conf *mdev)
+{
+	if (atomic_read(&mdev->local_cnt) >= mdev->net_conf->unplug_watermark)
+		drbd_kick_lo(mdev);
+}
+
+static void reclaim_net_ee(struct drbd_conf *mdev, struct list_head *to_be_freed)
+{
+	struct drbd_epoch_entry *e;
+	struct list_head *le, *tle;
+
+	/* The EEs are always appended to the end of the list. Since
+	   they are sent in order over the wire, they have to finish
+	   in order. As soon as we see the first not finished we can
+	   stop to examine the list... */
+
+	list_for_each_safe(le, tle, &mdev->net_ee) {
+		e = list_entry(le, struct drbd_epoch_entry, w.list);
+		if (drbd_bio_has_active_page(e->private_bio))
+			break;
+		list_move(le, to_be_freed);
+	}
+}
+
+static void drbd_kick_lo_and_reclaim_net(struct drbd_conf *mdev)
+{
+	LIST_HEAD(reclaimed);
+	struct drbd_epoch_entry *e, *t;
+
+	maybe_kick_lo(mdev);
+	spin_lock_irq(&mdev->req_lock);
+	reclaim_net_ee(mdev, &reclaimed);
+	spin_unlock_irq(&mdev->req_lock);
+
+	list_for_each_entry_safe(e, t, &reclaimed, w.list)
+		drbd_free_ee(mdev, e);
+}
+
+/**
+ * drbd_pp_alloc() - Returns a page, fails only if a signal comes in
+ * @mdev:	DRBD device.
+ * @retry:	whether or not to retry allocation forever (or until signalled)
+ *
+ * Tries to allocate a page, first from our own page pool, then from the
+ * kernel, unless this allocation would exceed the max_buffers setting.
+ * If @retry is non-zero, retry until DRBD frees a page somewhere else.
+ */
+static struct page *drbd_pp_alloc(struct drbd_conf *mdev, int retry)
+{
+	struct page *page = NULL;
+	DEFINE_WAIT(wait);
+
+	if (atomic_read(&mdev->pp_in_use) < mdev->net_conf->max_buffers) {
+		page = drbd_pp_first_page_or_try_alloc(mdev);
+		if (page)
+			return page;
+	}
+
+	for (;;) {
+		prepare_to_wait(&drbd_pp_wait, &wait, TASK_INTERRUPTIBLE);
+
+		drbd_kick_lo_and_reclaim_net(mdev);
+
+		if (atomic_read(&mdev->pp_in_use) < mdev->net_conf->max_buffers) {
+			page = drbd_pp_first_page_or_try_alloc(mdev);
+			if (page)
+				break;
+		}
+
+		if (!retry)
+			break;
+
+		if (signal_pending(current)) {
+			dev_warn(DEV, "drbd_pp_alloc interrupted!\n");
+			break;
+		}
+
+		schedule();
+	}
+	finish_wait(&drbd_pp_wait, &wait);
+
+	return page;
+}
+
+/* Must not be used from irq, as that may deadlock: see drbd_pp_alloc.
+ * Is also used from inside an other spin_lock_irq(&mdev->req_lock) */
+static void drbd_pp_free(struct drbd_conf *mdev, struct page *page)
+{
+	int free_it;
+
+	spin_lock(&drbd_pp_lock);
+	if (drbd_pp_vacant > (DRBD_MAX_SEGMENT_SIZE/PAGE_SIZE)*minor_count) {
+		free_it = 1;
+	} else {
+		set_page_private(page, (unsigned long)drbd_pp_pool);
+		drbd_pp_pool = page;
+		drbd_pp_vacant++;
+		free_it = 0;
+	}
+	spin_unlock(&drbd_pp_lock);
+
+	atomic_dec(&mdev->pp_in_use);
+
+	if (free_it)
+		__free_page(page);
+
+	wake_up(&drbd_pp_wait);
+}
+
+static void drbd_pp_free_bio_pages(struct drbd_conf *mdev, struct bio *bio)
+{
+	struct page *p_to_be_freed = NULL;
+	struct page *page;
+	struct bio_vec *bvec;
+	int i;
+
+	spin_lock(&drbd_pp_lock);
+	__bio_for_each_segment(bvec, bio, i, 0) {
+		if (drbd_pp_vacant > (DRBD_MAX_SEGMENT_SIZE/PAGE_SIZE)*minor_count) {
+			set_page_private(bvec->bv_page, (unsigned long)p_to_be_freed);
+			p_to_be_freed = bvec->bv_page;
+		} else {
+			set_page_private(bvec->bv_page, (unsigned long)drbd_pp_pool);
+			drbd_pp_pool = bvec->bv_page;
+			drbd_pp_vacant++;
+		}
+	}
+	spin_unlock(&drbd_pp_lock);
+	atomic_sub(bio->bi_vcnt, &mdev->pp_in_use);
+
+	while (p_to_be_freed) {
+		page = p_to_be_freed;
+		p_to_be_freed = (struct page *)page_private(page);
+		set_page_private(page, 0); /* just to be polite */
+		put_page(page);
+	}
+
+	wake_up(&drbd_pp_wait);
+}
+
+/*
+You need to hold the req_lock:
+ _drbd_wait_ee_list_empty()
+
+You must not have the req_lock:
+ drbd_free_ee()
+ drbd_alloc_ee()
+ drbd_init_ee()
+ drbd_release_ee()
+ drbd_ee_fix_bhs()
+ drbd_process_done_ee()
+ drbd_clear_done_ee()
+ drbd_wait_ee_list_empty()
+*/
+
+struct drbd_epoch_entry *drbd_alloc_ee(struct drbd_conf *mdev,
+				     u64 id,
+				     sector_t sector,
+				     unsigned int data_size,
+				     gfp_t gfp_mask) __must_hold(local)
+{
+	struct request_queue *q;
+	struct drbd_epoch_entry *e;
+	struct page *page;
+	struct bio *bio;
+	unsigned int ds;
+
+	if (FAULT_ACTIVE(mdev, DRBD_FAULT_AL_EE))
+		return NULL;
+
+	e = mempool_alloc(drbd_ee_mempool, gfp_mask & ~__GFP_HIGHMEM);
+	if (!e) {
+		if (!(gfp_mask & __GFP_NOWARN))
+			dev_err(DEV, "alloc_ee: Allocation of an EE failed\n");
+		return NULL;
+	}
+
+	bio = bio_alloc(gfp_mask & ~__GFP_HIGHMEM, div_ceil(data_size, PAGE_SIZE));
+	if (!bio) {
+		if (!(gfp_mask & __GFP_NOWARN))
+			dev_err(DEV, "alloc_ee: Allocation of a bio failed\n");
+		goto fail1;
+	}
+
+	bio->bi_bdev = mdev->ldev->backing_bdev;
+	bio->bi_sector = sector;
+
+	ds = data_size;
+	while (ds) {
+		page = drbd_pp_alloc(mdev, (gfp_mask & __GFP_WAIT));
+		if (!page) {
+			if (!(gfp_mask & __GFP_NOWARN))
+				dev_err(DEV, "alloc_ee: Allocation of a page failed\n");
+			goto fail2;
+		}
+		if (!bio_add_page(bio, page, min_t(int, ds, PAGE_SIZE), 0)) {
+			drbd_pp_free(mdev, page);
+			dev_err(DEV, "alloc_ee: bio_add_page(s=%llu,"
+			    "data_size=%u,ds=%u) failed\n",
+			    (unsigned long long)sector, data_size, ds);
+
+			q = bdev_get_queue(bio->bi_bdev);
+			if (q->merge_bvec_fn) {
+				struct bvec_merge_data bvm = {
+					.bi_bdev = bio->bi_bdev,
+					.bi_sector = bio->bi_sector,
+					.bi_size = bio->bi_size,
+					.bi_rw = bio->bi_rw,
+				};
+				int l = q->merge_bvec_fn(q, &bvm,
+						&bio->bi_io_vec[bio->bi_vcnt]);
+				dev_err(DEV, "merge_bvec_fn() = %d\n", l);
+			}
+
+			/* dump more of the bio. */
+			dev_err(DEV, "bio->bi_max_vecs = %d\n", bio->bi_max_vecs);
+			dev_err(DEV, "bio->bi_vcnt = %d\n", bio->bi_vcnt);
+			dev_err(DEV, "bio->bi_size = %d\n", bio->bi_size);
+			dev_err(DEV, "bio->bi_phys_segments = %d\n", bio->bi_phys_segments);
+
+			goto fail2;
+			break;
+		}
+		ds -= min_t(int, ds, PAGE_SIZE);
+	}
+
+	D_ASSERT(data_size == bio->bi_size);
+
+	bio->bi_private = e;
+	e->mdev = mdev;
+	e->sector = sector;
+	e->size = bio->bi_size;
+
+	e->private_bio = bio;
+	e->block_id = id;
+	INIT_HLIST_NODE(&e->colision);
+	e->epoch = NULL;
+	e->flags = 0;
+
+	trace_drbd_ee(mdev, e, "allocated");
+
+	return e;
+
+ fail2:
+	drbd_pp_free_bio_pages(mdev, bio);
+	bio_put(bio);
+ fail1:
+	mempool_free(e, drbd_ee_mempool);
+
+	return NULL;
+}
+
+void drbd_free_ee(struct drbd_conf *mdev, struct drbd_epoch_entry *e)
+{
+	struct bio *bio = e->private_bio;
+	trace_drbd_ee(mdev, e, "freed");
+	drbd_pp_free_bio_pages(mdev, bio);
+	bio_put(bio);
+	D_ASSERT(hlist_unhashed(&e->colision));
+	mempool_free(e, drbd_ee_mempool);
+}
+
+int drbd_release_ee(struct drbd_conf *mdev, struct list_head *list)
+{
+	LIST_HEAD(work_list);
+	struct drbd_epoch_entry *e, *t;
+	int count = 0;
+
+	spin_lock_irq(&mdev->req_lock);
+	list_splice_init(list, &work_list);
+	spin_unlock_irq(&mdev->req_lock);
+
+	list_for_each_entry_safe(e, t, &work_list, w.list) {
+		drbd_free_ee(mdev, e);
+		count++;
+	}
+	return count;
+}
+
+
+/*
+ * This function is called from _asender only_
+ * but see also comments in _req_mod(,barrier_acked)
+ * and receive_Barrier.
+ *
+ * Move entries from net_ee to done_ee, if ready.
+ * Grab done_ee, call all callbacks, free the entries.
+ * The callbacks typically send out ACKs.
+ */
+static int drbd_process_done_ee(struct drbd_conf *mdev)
+{
+	LIST_HEAD(work_list);
+	LIST_HEAD(reclaimed);
+	struct drbd_epoch_entry *e, *t;
+	int ok = (mdev->state.conn >= C_WF_REPORT_PARAMS);
+
+	spin_lock_irq(&mdev->req_lock);
+	reclaim_net_ee(mdev, &reclaimed);
+	list_splice_init(&mdev->done_ee, &work_list);
+	spin_unlock_irq(&mdev->req_lock);
+
+	list_for_each_entry_safe(e, t, &reclaimed, w.list)
+		drbd_free_ee(mdev, e);
+
+	/* possible callbacks here:
+	 * e_end_block, and e_end_resync_block, e_send_discard_ack.
+	 * all ignore the last argument.
+	 */
+	list_for_each_entry_safe(e, t, &work_list, w.list) {
+		trace_drbd_ee(mdev, e, "process_done_ee");
+		/* list_del not necessary, next/prev members not touched */
+		ok = e->w.cb(mdev, &e->w, !ok) && ok;
+		drbd_free_ee(mdev, e);
+	}
+	wake_up(&mdev->ee_wait);
+
+	return ok;
+}
+
+void _drbd_wait_ee_list_empty(struct drbd_conf *mdev, struct list_head *head)
+{
+	DEFINE_WAIT(wait);
+
+	/* avoids spin_lock/unlock
+	 * and calling prepare_to_wait in the fast path */
+	while (!list_empty(head)) {
+		prepare_to_wait(&mdev->ee_wait, &wait, TASK_UNINTERRUPTIBLE);
+		spin_unlock_irq(&mdev->req_lock);
+		drbd_kick_lo(mdev);
+		schedule();
+		finish_wait(&mdev->ee_wait, &wait);
+		spin_lock_irq(&mdev->req_lock);
+	}
+}
+
+void drbd_wait_ee_list_empty(struct drbd_conf *mdev, struct list_head *head)
+{
+	spin_lock_irq(&mdev->req_lock);
+	_drbd_wait_ee_list_empty(mdev, head);
+	spin_unlock_irq(&mdev->req_lock);
+}
+
+/* see also kernel_accept; which is only present since 2.6.18.
+ * also we want to log which part of it failed, exactly */
+static int drbd_accept(struct drbd_conf *mdev, const char **what,
+		struct socket *sock, struct socket **newsock)
+{
+	struct sock *sk = sock->sk;
+	int err = 0;
+
+	*what = "listen";
+	err = sock->ops->listen(sock, 5);
+	if (err < 0)
+		goto out;
+
+	*what = "sock_create_lite";
+	err = sock_create_lite(sk->sk_family, sk->sk_type, sk->sk_protocol,
+			       newsock);
+	if (err < 0)
+		goto out;
+
+	*what = "accept";
+	err = sock->ops->accept(sock, *newsock, 0);
+	if (err < 0) {
+		sock_release(*newsock);
+		*newsock = NULL;
+		goto out;
+	}
+	(*newsock)->ops  = sock->ops;
+
+out:
+	return err;
+}
+
+static int drbd_recv_short(struct drbd_conf *mdev, struct socket *sock,
+		    void *buf, size_t size, int flags)
+{
+	mm_segment_t oldfs;
+	struct kvec iov = {
+		.iov_base = buf,
+		.iov_len = size,
+	};
+	struct msghdr msg = {
+		.msg_iovlen = 1,
+		.msg_iov = (struct iovec *)&iov,
+		.msg_flags = (flags ? flags : MSG_WAITALL | MSG_NOSIGNAL)
+	};
+	int rv;
+
+	oldfs = get_fs();
+	set_fs(KERNEL_DS);
+	rv = sock_recvmsg(sock, &msg, size, msg.msg_flags);
+	set_fs(oldfs);
+
+	return rv;
+}
+
+static int drbd_recv(struct drbd_conf *mdev, void *buf, size_t size)
+{
+	mm_segment_t oldfs;
+	struct kvec iov = {
+		.iov_base = buf,
+		.iov_len = size,
+	};
+	struct msghdr msg = {
+		.msg_iovlen = 1,
+		.msg_iov = (struct iovec *)&iov,
+		.msg_flags = MSG_WAITALL | MSG_NOSIGNAL
+	};
+	int rv;
+
+	oldfs = get_fs();
+	set_fs(KERNEL_DS);
+
+	for (;;) {
+		rv = sock_recvmsg(mdev->data.socket, &msg, size, msg.msg_flags);
+		if (rv == size)
+			break;
+
+		/* Note:
+		 * ECONNRESET	other side closed the connection
+		 * ERESTARTSYS	(on  sock) we got a signal
+		 */
+
+		if (rv < 0) {
+			if (rv == -ECONNRESET)
+				dev_info(DEV, "sock was reset by peer\n");
+			else if (rv != -ERESTARTSYS)
+				dev_err(DEV, "sock_recvmsg returned %d\n", rv);
+			break;
+		} else if (rv == 0) {
+			dev_info(DEV, "sock was shut down by peer\n");
+			break;
+		} else	{
+			/* signal came in, or peer/link went down,
+			 * after we read a partial message
+			 */
+			/* D_ASSERT(signal_pending(current)); */
+			break;
+		}
+	};
+
+	set_fs(oldfs);
+
+	if (rv != size)
+		drbd_force_state(mdev, NS(conn, C_BROKEN_PIPE));
+
+	return rv;
+}
+
+static struct socket *drbd_try_connect(struct drbd_conf *mdev)
+{
+	const char *what;
+	struct socket *sock;
+	struct sockaddr_in6 src_in6;
+	int err;
+	int disconnect_on_error = 1;
+
+	if (!get_net_conf(mdev))
+		return NULL;
+
+	what = "sock_create_kern";
+	err = sock_create_kern(((struct sockaddr *)mdev->net_conf->my_addr)->sa_family,
+		SOCK_STREAM, IPPROTO_TCP, &sock);
+	if (err < 0) {
+		sock = NULL;
+		goto out;
+	}
+
+	sock->sk->sk_rcvtimeo =
+	sock->sk->sk_sndtimeo =  mdev->net_conf->try_connect_int*HZ;
+
+       /* explicitly bind to the configured IP as source IP
+	*  for the outgoing connections.
+	*  This is needed for multihomed hosts and to be
+	*  able to use lo: interfaces for drbd.
+	* Make sure to use 0 as port number, so linux selects
+	*  a free one dynamically.
+	*/
+	memcpy(&src_in6, mdev->net_conf->my_addr,
+	       min_t(int, mdev->net_conf->my_addr_len, sizeof(src_in6)));
+	if (((struct sockaddr *)mdev->net_conf->my_addr)->sa_family == AF_INET6)
+		src_in6.sin6_port = 0;
+	else
+		((struct sockaddr_in *)&src_in6)->sin_port = 0; /* AF_INET & AF_SCI */
+
+	what = "bind before connect";
+	err = sock->ops->bind(sock,
+			      (struct sockaddr *) &src_in6,
+			      mdev->net_conf->my_addr_len);
+	if (err < 0)
+		goto out;
+
+	/* connect may fail, peer not yet available.
+	 * stay C_WF_CONNECTION, don't go Disconnecting! */
+	disconnect_on_error = 0;
+	what = "connect";
+	err = sock->ops->connect(sock,
+				 (struct sockaddr *)mdev->net_conf->peer_addr,
+				 mdev->net_conf->peer_addr_len, 0);
+
+out:
+	if (err < 0) {
+		if (sock) {
+			sock_release(sock);
+			sock = NULL;
+		}
+		switch (-err) {
+			/* timeout, busy, signal pending */
+		case ETIMEDOUT: case EAGAIN: case EINPROGRESS:
+		case EINTR: case ERESTARTSYS:
+			/* peer not (yet) available, network problem */
+		case ECONNREFUSED: case ENETUNREACH:
+		case EHOSTDOWN:    case EHOSTUNREACH:
+			disconnect_on_error = 0;
+			break;
+		default:
+			dev_err(DEV, "%s failed, err = %d\n", what, err);
+		}
+		if (disconnect_on_error)
+			drbd_force_state(mdev, NS(conn, C_DISCONNECTING));
+	}
+	put_net_conf(mdev);
+	return sock;
+}
+
+static struct socket *drbd_wait_for_connect(struct drbd_conf *mdev)
+{
+	int timeo, err;
+	struct socket *s_estab = NULL, *s_listen;
+	const char *what;
+
+	if (!get_net_conf(mdev))
+		return NULL;
+
+	what = "sock_create_kern";
+	err = sock_create_kern(((struct sockaddr *)mdev->net_conf->my_addr)->sa_family,
+		SOCK_STREAM, IPPROTO_TCP, &s_listen);
+	if (err) {
+		s_listen = NULL;
+		goto out;
+	}
+
+	timeo = mdev->net_conf->try_connect_int * HZ;
+	timeo += (random32() & 1) ? timeo / 7 : -timeo / 7; /* 28.5% random jitter */
+
+	s_listen->sk->sk_reuse    = 1; /* SO_REUSEADDR */
+	s_listen->sk->sk_rcvtimeo = timeo;
+	s_listen->sk->sk_sndtimeo = timeo;
+
+	what = "bind before listen";
+	err = s_listen->ops->bind(s_listen,
+			      (struct sockaddr *) mdev->net_conf->my_addr,
+			      mdev->net_conf->my_addr_len);
+	if (err < 0)
+		goto out;
+
+	err = drbd_accept(mdev, &what, s_listen, &s_estab);
+
+out:
+	if (s_listen)
+		sock_release(s_listen);
+	if (err < 0) {
+		if (err != -EAGAIN && err != -EINTR && err != -ERESTARTSYS) {
+			dev_err(DEV, "%s failed, err = %d\n", what, err);
+			drbd_force_state(mdev, NS(conn, C_DISCONNECTING));
+		}
+	}
+	put_net_conf(mdev);
+
+	return s_estab;
+}
+
+static int drbd_send_fp(struct drbd_conf *mdev,
+	struct socket *sock, enum drbd_packets cmd)
+{
+	struct p_header *h = (struct p_header *) &mdev->data.sbuf.header;
+
+	return _drbd_send_cmd(mdev, sock, cmd, h, sizeof(*h), 0);
+}
+
+static enum drbd_packets drbd_recv_fp(struct drbd_conf *mdev, struct socket *sock)
+{
+	struct p_header *h = (struct p_header *) &mdev->data.sbuf.header;
+	int rr;
+
+	rr = drbd_recv_short(mdev, sock, h, sizeof(*h), 0);
+
+	if (rr == sizeof(*h) && h->magic == BE_DRBD_MAGIC)
+		return be16_to_cpu(h->command);
+
+	return 0xffff;
+}
+
+/**
+ * drbd_socket_okay() - Free the socket if its connection is not okay
+ * @mdev:	DRBD device.
+ * @sock:	pointer to the pointer to the socket.
+ */
+static int drbd_socket_okay(struct drbd_conf *mdev, struct socket **sock)
+{
+	int rr;
+	char tb[4];
+
+	if (!*sock)
+		return FALSE;
+
+	rr = drbd_recv_short(mdev, *sock, tb, 4, MSG_DONTWAIT | MSG_PEEK);
+
+	if (rr > 0 || rr == -EAGAIN) {
+		return TRUE;
+	} else {
+		sock_release(*sock);
+		*sock = NULL;
+		return FALSE;
+	}
+}
+
+/*
+ * return values:
+ *   1 yes, we have a valid connection
+ *   0 oops, did not work out, please try again
+ *  -1 peer talks different language,
+ *     no point in trying again, please go standalone.
+ *  -2 We do not have a network config...
+ */
+static int drbd_connect(struct drbd_conf *mdev)
+{
+	struct socket *s, *sock, *msock;
+	int try, h, ok;
+
+	D_ASSERT(!mdev->data.socket);
+
+	if (test_and_clear_bit(CREATE_BARRIER, &mdev->flags))
+		dev_err(DEV, "CREATE_BARRIER flag was set in drbd_connect - now cleared!\n");
+
+	if (drbd_request_state(mdev, NS(conn, C_WF_CONNECTION)) < SS_SUCCESS)
+		return -2;
+
+	clear_bit(DISCARD_CONCURRENT, &mdev->flags);
+
+	sock  = NULL;
+	msock = NULL;
+
+	do {
+		for (try = 0;;) {
+			/* 3 tries, this should take less than a second! */
+			s = drbd_try_connect(mdev);
+			if (s || ++try >= 3)
+				break;
+			/* give the other side time to call bind() & listen() */
+			__set_current_state(TASK_INTERRUPTIBLE);
+			schedule_timeout(HZ / 10);
+		}
+
+		if (s) {
+			if (!sock) {
+				drbd_send_fp(mdev, s, P_HAND_SHAKE_S);
+				sock = s;
+				s = NULL;
+			} else if (!msock) {
+				drbd_send_fp(mdev, s, P_HAND_SHAKE_M);
+				msock = s;
+				s = NULL;
+			} else {
+				dev_err(DEV, "Logic error in drbd_connect()\n");
+				goto out_release_sockets;
+			}
+		}
+
+		if (sock && msock) {
+			__set_current_state(TASK_INTERRUPTIBLE);
+			schedule_timeout(HZ / 10);
+			ok = drbd_socket_okay(mdev, &sock);
+			ok = drbd_socket_okay(mdev, &msock) && ok;
+			if (ok)
+				break;
+		}
+
+retry:
+		s = drbd_wait_for_connect(mdev);
+		if (s) {
+			try = drbd_recv_fp(mdev, s);
+			drbd_socket_okay(mdev, &sock);
+			drbd_socket_okay(mdev, &msock);
+			switch (try) {
+			case P_HAND_SHAKE_S:
+				if (sock) {
+					dev_warn(DEV, "initial packet S crossed\n");
+					sock_release(sock);
+				}
+				sock = s;
+				break;
+			case P_HAND_SHAKE_M:
+				if (msock) {
+					dev_warn(DEV, "initial packet M crossed\n");
+					sock_release(msock);
+				}
+				msock = s;
+				set_bit(DISCARD_CONCURRENT, &mdev->flags);
+				break;
+			default:
+				dev_warn(DEV, "Error receiving initial packet\n");
+				sock_release(s);
+				if (random32() & 1)
+					goto retry;
+			}
+		}
+
+		if (mdev->state.conn <= C_DISCONNECTING)
+			goto out_release_sockets;
+		if (signal_pending(current)) {
+			flush_signals(current);
+			smp_rmb();
+			if (get_t_state(&mdev->receiver) == Exiting)
+				goto out_release_sockets;
+		}
+
+		if (sock && msock) {
+			ok = drbd_socket_okay(mdev, &sock);
+			ok = drbd_socket_okay(mdev, &msock) && ok;
+			if (ok)
+				break;
+		}
+	} while (1);
+
+	msock->sk->sk_reuse = 1; /* SO_REUSEADDR */
+	sock->sk->sk_reuse = 1; /* SO_REUSEADDR */
+
+	sock->sk->sk_allocation = GFP_NOIO;
+	msock->sk->sk_allocation = GFP_NOIO;
+
+	sock->sk->sk_priority = TC_PRIO_INTERACTIVE_BULK;
+	msock->sk->sk_priority = TC_PRIO_INTERACTIVE;
+
+	if (mdev->net_conf->sndbuf_size) {
+		sock->sk->sk_sndbuf = mdev->net_conf->sndbuf_size;
+		sock->sk->sk_userlocks |= SOCK_SNDBUF_LOCK;
+	}
+
+	if (mdev->net_conf->rcvbuf_size) {
+		sock->sk->sk_rcvbuf = mdev->net_conf->rcvbuf_size;
+		sock->sk->sk_userlocks |= SOCK_RCVBUF_LOCK;
+	}
+
+	/* NOT YET ...
+	 * sock->sk->sk_sndtimeo = mdev->net_conf->timeout*HZ/10;
+	 * sock->sk->sk_rcvtimeo = MAX_SCHEDULE_TIMEOUT;
+	 * first set it to the P_HAND_SHAKE timeout,
+	 * which we set to 4x the configured ping_timeout. */
+	sock->sk->sk_sndtimeo =
+	sock->sk->sk_rcvtimeo = mdev->net_conf->ping_timeo*4*HZ/10;
+
+	msock->sk->sk_sndtimeo = mdev->net_conf->timeout*HZ/10;
+	msock->sk->sk_rcvtimeo = mdev->net_conf->ping_int*HZ;
+
+	/* we don't want delays.
+	 * we use TCP_CORK where apropriate, though */
+	drbd_tcp_nodelay(sock);
+	drbd_tcp_nodelay(msock);
+
+	mdev->data.socket = sock;
+	mdev->meta.socket = msock;
+	mdev->last_received = jiffies;
+
+	D_ASSERT(mdev->asender.task == NULL);
+
+	h = drbd_do_handshake(mdev);
+	if (h <= 0)
+		return h;
+
+	if (mdev->cram_hmac_tfm) {
+		/* drbd_request_state(mdev, NS(conn, WFAuth)); */
+		if (!drbd_do_auth(mdev)) {
+			dev_err(DEV, "Authentication of peer failed\n");
+			return -1;
+		}
+	}
+
+	if (drbd_request_state(mdev, NS(conn, C_WF_REPORT_PARAMS)) < SS_SUCCESS)
+		return 0;
+
+	sock->sk->sk_sndtimeo = mdev->net_conf->timeout*HZ/10;
+	sock->sk->sk_rcvtimeo = MAX_SCHEDULE_TIMEOUT;
+
+	atomic_set(&mdev->packet_seq, 0);
+	mdev->peer_seq = 0;
+
+	drbd_thread_start(&mdev->asender);
+
+	drbd_send_protocol(mdev);
+	drbd_send_sync_param(mdev, &mdev->sync_conf);
+	drbd_send_sizes(mdev, 0);
+	drbd_send_uuids(mdev);
+	drbd_send_state(mdev);
+	clear_bit(USE_DEGR_WFC_T, &mdev->flags);
+	clear_bit(RESIZE_PENDING, &mdev->flags);
+
+	return 1;
+
+out_release_sockets:
+	if (sock)
+		sock_release(sock);
+	if (msock)
+		sock_release(msock);
+	return -1;
+}
+
+static int drbd_recv_header(struct drbd_conf *mdev, struct p_header *h)
+{
+	int r;
+
+	r = drbd_recv(mdev, h, sizeof(*h));
+
+	if (unlikely(r != sizeof(*h))) {
+		dev_err(DEV, "short read expecting header on sock: r=%d\n", r);
+		return FALSE;
+	};
+	h->command = be16_to_cpu(h->command);
+	h->length  = be16_to_cpu(h->length);
+	if (unlikely(h->magic != BE_DRBD_MAGIC)) {
+		dev_err(DEV, "magic?? on data m: 0x%lx c: %d l: %d\n",
+		    (long)be32_to_cpu(h->magic),
+		    h->command, h->length);
+		return FALSE;
+	}
+	mdev->last_received = jiffies;
+
+	return TRUE;
+}
+
+static enum finish_epoch drbd_flush_after_epoch(struct drbd_conf *mdev, struct drbd_epoch *epoch)
+{
+	int rv;
+
+	if (mdev->write_ordering >= WO_bdev_flush && get_ldev(mdev)) {
+		rv = blkdev_issue_flush(mdev->ldev->backing_bdev, NULL);
+		if (rv) {
+			dev_err(DEV, "local disk flush failed with status %d\n", rv);
+			/* would rather check on EOPNOTSUPP, but that is not reliable.
+			 * don't try again for ANY return value != 0
+			 * if (rv == -EOPNOTSUPP) */
+			drbd_bump_write_ordering(mdev, WO_drain_io);
+		}
+		put_ldev(mdev);
+	}
+
+	return drbd_may_finish_epoch(mdev, epoch, EV_BARRIER_DONE);
+}
+
+static int w_flush(struct drbd_conf *mdev, struct drbd_work *w, int cancel)
+{
+	struct flush_work *fw = (struct flush_work *)w;
+	struct drbd_epoch *epoch = fw->epoch;
+
+	kfree(w);
+
+	if (!test_and_set_bit(DE_BARRIER_IN_NEXT_EPOCH_ISSUED, &epoch->flags))
+		drbd_flush_after_epoch(mdev, epoch);
+
+	drbd_may_finish_epoch(mdev, epoch, EV_PUT |
+			      (mdev->state.conn < C_CONNECTED ? EV_CLEANUP : 0));
+
+	return 1;
+}
+
+/**
+ * drbd_may_finish_epoch() - Applies an epoch_event to the epoch's state, eventually finishes it.
+ * @mdev:	DRBD device.
+ * @epoch:	Epoch object.
+ * @ev:		Epoch event.
+ */
+static enum finish_epoch drbd_may_finish_epoch(struct drbd_conf *mdev,
+					       struct drbd_epoch *epoch,
+					       enum epoch_event ev)
+{
+	int finish, epoch_size;
+	struct drbd_epoch *next_epoch;
+	int schedule_flush = 0;
+	enum finish_epoch rv = FE_STILL_LIVE;
+
+	spin_lock(&mdev->epoch_lock);
+	do {
+		next_epoch = NULL;
+		finish = 0;
+
+		epoch_size = atomic_read(&epoch->epoch_size);
+
+		switch (ev & ~EV_CLEANUP) {
+		case EV_PUT:
+			atomic_dec(&epoch->active);
+			break;
+		case EV_GOT_BARRIER_NR:
+			set_bit(DE_HAVE_BARRIER_NUMBER, &epoch->flags);
+
+			/* Special case: If we just switched from WO_bio_barrier to
+			   WO_bdev_flush we should not finish the current epoch */
+			if (test_bit(DE_CONTAINS_A_BARRIER, &epoch->flags) && epoch_size == 1 &&
+			    mdev->write_ordering != WO_bio_barrier &&
+			    epoch == mdev->current_epoch)
+				clear_bit(DE_CONTAINS_A_BARRIER, &epoch->flags);
+			break;
+		case EV_BARRIER_DONE:
+			set_bit(DE_BARRIER_IN_NEXT_EPOCH_DONE, &epoch->flags);
+			break;
+		case EV_BECAME_LAST:
+			/* nothing to do*/
+			break;
+		}
+
+		trace_drbd_epoch(mdev, epoch, ev);
+
+		if (epoch_size != 0 &&
+		    atomic_read(&epoch->active) == 0 &&
+		    test_bit(DE_HAVE_BARRIER_NUMBER, &epoch->flags) &&
+		    epoch->list.prev == &mdev->current_epoch->list &&
+		    !test_bit(DE_IS_FINISHING, &epoch->flags)) {
+			/* Nearly all conditions are met to finish that epoch... */
+			if (test_bit(DE_BARRIER_IN_NEXT_EPOCH_DONE, &epoch->flags) ||
+			    mdev->write_ordering == WO_none ||
+			    (epoch_size == 1 && test_bit(DE_CONTAINS_A_BARRIER, &epoch->flags)) ||
+			    ev & EV_CLEANUP) {
+				finish = 1;
+				set_bit(DE_IS_FINISHING, &epoch->flags);
+			} else if (!test_bit(DE_BARRIER_IN_NEXT_EPOCH_ISSUED, &epoch->flags) &&
+				 mdev->write_ordering == WO_bio_barrier) {
+				atomic_inc(&epoch->active);
+				schedule_flush = 1;
+			}
+		}
+		if (finish) {
+			if (!(ev & EV_CLEANUP)) {
+				spin_unlock(&mdev->epoch_lock);
+				drbd_send_b_ack(mdev, epoch->barrier_nr, epoch_size);
+				spin_lock(&mdev->epoch_lock);
+			}
+			dec_unacked(mdev);
+
+			if (mdev->current_epoch != epoch) {
+				next_epoch = list_entry(epoch->list.next, struct drbd_epoch, list);
+				list_del(&epoch->list);
+				ev = EV_BECAME_LAST | (ev & EV_CLEANUP);
+				mdev->epochs--;
+				trace_drbd_epoch(mdev, epoch, EV_TRACE_FREE);
+				kfree(epoch);
+
+				if (rv == FE_STILL_LIVE)
+					rv = FE_DESTROYED;
+			} else {
+				epoch->flags = 0;
+				atomic_set(&epoch->epoch_size, 0);
+				/* atomic_set(&epoch->active, 0); is alrady zero */
+				if (rv == FE_STILL_LIVE)
+					rv = FE_RECYCLED;
+			}
+		}
+
+		if (!next_epoch)
+			break;
+
+		epoch = next_epoch;
+	} while (1);
+
+	spin_unlock(&mdev->epoch_lock);
+
+	if (schedule_flush) {
+		struct flush_work *fw;
+		fw = kmalloc(sizeof(*fw), GFP_ATOMIC);
+		if (fw) {
+			trace_drbd_epoch(mdev, epoch, EV_TRACE_FLUSH);
+			fw->w.cb = w_flush;
+			fw->epoch = epoch;
+			drbd_queue_work(&mdev->data.work, &fw->w);
+		} else {
+			dev_warn(DEV, "Could not kmalloc a flush_work obj\n");
+			set_bit(DE_BARRIER_IN_NEXT_EPOCH_ISSUED, &epoch->flags);
+			/* That is not a recursion, only one level */
+			drbd_may_finish_epoch(mdev, epoch, EV_BARRIER_DONE);
+			drbd_may_finish_epoch(mdev, epoch, EV_PUT);
+		}
+	}
+
+	return rv;
+}
+
+/**
+ * drbd_bump_write_ordering() - Fall back to an other write ordering method
+ * @mdev:	DRBD device.
+ * @wo:		Write ordering method to try.
+ */
+void drbd_bump_write_ordering(struct drbd_conf *mdev, enum write_ordering_e wo) __must_hold(local)
+{
+	enum write_ordering_e pwo;
+	static char *write_ordering_str[] = {
+		[WO_none] = "none",
+		[WO_drain_io] = "drain",
+		[WO_bdev_flush] = "flush",
+		[WO_bio_barrier] = "barrier",
+	};
+
+	pwo = mdev->write_ordering;
+	wo = min(pwo, wo);
+	if (wo == WO_bio_barrier && mdev->ldev->dc.no_disk_barrier)
+		wo = WO_bdev_flush;
+	if (wo == WO_bdev_flush && mdev->ldev->dc.no_disk_flush)
+		wo = WO_drain_io;
+	if (wo == WO_drain_io && mdev->ldev->dc.no_disk_drain)
+		wo = WO_none;
+	mdev->write_ordering = wo;
+	if (pwo != mdev->write_ordering || wo == WO_bio_barrier)
+		dev_info(DEV, "Method to ensure write ordering: %s\n", write_ordering_str[mdev->write_ordering]);
+}
+
+/**
+ * w_e_reissue() - Worker callback; Resubmit a bio, without BIO_RW_BARRIER set
+ * @mdev:	DRBD device.
+ * @w:		work object.
+ * @cancel:	The connection will be closed anyways (unused in this callback)
+ */
+int w_e_reissue(struct drbd_conf *mdev, struct drbd_work *w, int cancel) __releases(local)
+{
+	struct drbd_epoch_entry *e = (struct drbd_epoch_entry *)w;
+	struct bio *bio = e->private_bio;
+
+	/* We leave DE_CONTAINS_A_BARRIER and EE_IS_BARRIER in place,
+	   (and DE_BARRIER_IN_NEXT_EPOCH_ISSUED in the previous Epoch)
+	   so that we can finish that epoch in drbd_may_finish_epoch().
+	   That is necessary if we already have a long chain of Epochs, before
+	   we realize that BIO_RW_BARRIER is actually not supported */
+
+	/* As long as the -ENOTSUPP on the barrier is reported immediately
+	   that will never trigger. If it is reported late, we will just
+	   print that warning and continue correctly for all future requests
+	   with WO_bdev_flush */
+	if (previous_epoch(mdev, e->epoch))
+		dev_warn(DEV, "Write ordering was not enforced (one time event)\n");
+
+	/* prepare bio for re-submit,
+	 * re-init volatile members */
+	/* we still have a local reference,
+	 * get_ldev was done in receive_Data. */
+	bio->bi_bdev = mdev->ldev->backing_bdev;
+	bio->bi_sector = e->sector;
+	bio->bi_size = e->size;
+	bio->bi_idx = 0;
+
+	bio->bi_flags &= ~(BIO_POOL_MASK - 1);
+	bio->bi_flags |= 1 << BIO_UPTODATE;
+
+	/* don't know whether this is necessary: */
+	bio->bi_phys_segments = 0;
+	bio->bi_next = NULL;
+
+	/* these should be unchanged: */
+	/* bio->bi_end_io = drbd_endio_write_sec; */
+	/* bio->bi_vcnt = whatever; */
+
+	e->w.cb = e_end_block;
+
+	/* This is no longer a barrier request. */
+	bio->bi_rw &= ~(1UL << BIO_RW_BARRIER);
+
+	drbd_generic_make_request(mdev, DRBD_FAULT_DT_WR, bio);
+
+	return 1;
+}
+
+static int receive_Barrier(struct drbd_conf *mdev, struct p_header *h)
+{
+	int rv, issue_flush;
+	struct p_barrier *p = (struct p_barrier *)h;
+	struct drbd_epoch *epoch;
+
+	ERR_IF(h->length != (sizeof(*p)-sizeof(*h))) return FALSE;
+
+	rv = drbd_recv(mdev, h->payload, h->length);
+	ERR_IF(rv != h->length) return FALSE;
+
+	inc_unacked(mdev);
+
+	if (mdev->net_conf->wire_protocol != DRBD_PROT_C)
+		drbd_kick_lo(mdev);
+
+	mdev->current_epoch->barrier_nr = p->barrier;
+	rv = drbd_may_finish_epoch(mdev, mdev->current_epoch, EV_GOT_BARRIER_NR);
+
+	/* P_BARRIER_ACK may imply that the corresponding extent is dropped from
+	 * the activity log, which means it would not be resynced in case the
+	 * R_PRIMARY crashes now.
+	 * Therefore we must send the barrier_ack after the barrier request was
+	 * completed. */
+	switch (mdev->write_ordering) {
+	case WO_bio_barrier:
+	case WO_none:
+		if (rv == FE_RECYCLED)
+			return TRUE;
+		break;
+
+	case WO_bdev_flush:
+	case WO_drain_io:
+		D_ASSERT(rv == FE_STILL_LIVE);
+		set_bit(DE_BARRIER_IN_NEXT_EPOCH_ISSUED, &mdev->current_epoch->flags);
+		drbd_wait_ee_list_empty(mdev, &mdev->active_ee);
+		rv = drbd_flush_after_epoch(mdev, mdev->current_epoch);
+		if (rv == FE_RECYCLED)
+			return TRUE;
+
+		/* The asender will send all the ACKs and barrier ACKs out, since
+		   all EEs moved from the active_ee to the done_ee. We need to
+		   provide a new epoch object for the EEs that come in soon */
+		break;
+	}
+
+	/* receiver context, in the writeout path of the other node.
+	 * avoid potential distributed deadlock */
+	epoch = kmalloc(sizeof(struct drbd_epoch), GFP_NOIO);
+	if (!epoch) {
+		dev_warn(DEV, "Allocation of an epoch failed, slowing down\n");
+		issue_flush = !test_and_set_bit(DE_BARRIER_IN_NEXT_EPOCH_ISSUED, &epoch->flags);
+		drbd_wait_ee_list_empty(mdev, &mdev->active_ee);
+		if (issue_flush) {
+			rv = drbd_flush_after_epoch(mdev, mdev->current_epoch);
+			if (rv == FE_RECYCLED)
+				return TRUE;
+		}
+
+		drbd_wait_ee_list_empty(mdev, &mdev->done_ee);
+
+		return TRUE;
+	}
+
+	epoch->flags = 0;
+	atomic_set(&epoch->epoch_size, 0);
+	atomic_set(&epoch->active, 0);
+
+	spin_lock(&mdev->epoch_lock);
+	if (atomic_read(&mdev->current_epoch->epoch_size)) {
+		list_add(&epoch->list, &mdev->current_epoch->list);
+		mdev->current_epoch = epoch;
+		mdev->epochs++;
+		trace_drbd_epoch(mdev, epoch, EV_TRACE_ALLOC);
+	} else {
+		/* The current_epoch got recycled while we allocated this one... */
+		kfree(epoch);
+	}
+	spin_unlock(&mdev->epoch_lock);
+
+	return TRUE;
+}
+
+/* used from receive_RSDataReply (recv_resync_read)
+ * and from receive_Data */
+static struct drbd_epoch_entry *
+read_in_block(struct drbd_conf *mdev, u64 id, sector_t sector, int data_size) __must_hold(local)
+{
+	struct drbd_epoch_entry *e;
+	struct bio_vec *bvec;
+	struct page *page;
+	struct bio *bio;
+	int dgs, ds, i, rr;
+	void *dig_in = mdev->int_dig_in;
+	void *dig_vv = mdev->int_dig_vv;
+
+	dgs = (mdev->agreed_pro_version >= 87 && mdev->integrity_r_tfm) ?
+		crypto_hash_digestsize(mdev->integrity_r_tfm) : 0;
+
+	if (dgs) {
+		rr = drbd_recv(mdev, dig_in, dgs);
+		if (rr != dgs) {
+			dev_warn(DEV, "short read receiving data digest: read %d expected %d\n",
+			     rr, dgs);
+			return NULL;
+		}
+	}
+
+	data_size -= dgs;
+
+	ERR_IF(data_size &  0x1ff) return NULL;
+	ERR_IF(data_size >  DRBD_MAX_SEGMENT_SIZE) return NULL;
+
+	/* GFP_NOIO, because we must not cause arbitrary write-out: in a DRBD
+	 * "criss-cross" setup, that might cause write-out on some other DRBD,
+	 * which in turn might block on the other node at this very place.  */
+	e = drbd_alloc_ee(mdev, id, sector, data_size, GFP_NOIO);
+	if (!e)
+		return NULL;
+	bio = e->private_bio;
+	ds = data_size;
+	bio_for_each_segment(bvec, bio, i) {
+		page = bvec->bv_page;
+		rr = drbd_recv(mdev, kmap(page), min_t(int, ds, PAGE_SIZE));
+		kunmap(page);
+		if (rr != min_t(int, ds, PAGE_SIZE)) {
+			drbd_free_ee(mdev, e);
+			dev_warn(DEV, "short read receiving data: read %d expected %d\n",
+			     rr, min_t(int, ds, PAGE_SIZE));
+			return NULL;
+		}
+		ds -= rr;
+	}
+
+	if (dgs) {
+		drbd_csum(mdev, mdev->integrity_r_tfm, bio, dig_vv);
+		if (memcmp(dig_in, dig_vv, dgs)) {
+			dev_err(DEV, "Digest integrity check FAILED.\n");
+			drbd_bcast_ee(mdev, "digest failed",
+					dgs, dig_in, dig_vv, e);
+			drbd_free_ee(mdev, e);
+			return NULL;
+		}
+	}
+	mdev->recv_cnt += data_size>>9;
+	return e;
+}
+
+/* drbd_drain_block() just takes a data block
+ * out of the socket input buffer, and discards it.
+ */
+static int drbd_drain_block(struct drbd_conf *mdev, int data_size)
+{
+	struct page *page;
+	int rr, rv = 1;
+	void *data;
+
+	page = drbd_pp_alloc(mdev, 1);
+
+	data = kmap(page);
+	while (data_size) {
+		rr = drbd_recv(mdev, data, min_t(int, data_size, PAGE_SIZE));
+		if (rr != min_t(int, data_size, PAGE_SIZE)) {
+			rv = 0;
+			dev_warn(DEV, "short read receiving data: read %d expected %d\n",
+			     rr, min_t(int, data_size, PAGE_SIZE));
+			break;
+		}
+		data_size -= rr;
+	}
+	kunmap(page);
+	drbd_pp_free(mdev, page);
+	return rv;
+}
+
+static int recv_dless_read(struct drbd_conf *mdev, struct drbd_request *req,
+			   sector_t sector, int data_size)
+{
+	struct bio_vec *bvec;
+	struct bio *bio;
+	int dgs, rr, i, expect;
+	void *dig_in = mdev->int_dig_in;
+	void *dig_vv = mdev->int_dig_vv;
+
+	dgs = (mdev->agreed_pro_version >= 87 && mdev->integrity_r_tfm) ?
+		crypto_hash_digestsize(mdev->integrity_r_tfm) : 0;
+
+	if (dgs) {
+		rr = drbd_recv(mdev, dig_in, dgs);
+		if (rr != dgs) {
+			dev_warn(DEV, "short read receiving data reply digest: read %d expected %d\n",
+			     rr, dgs);
+			return 0;
+		}
+	}
+
+	data_size -= dgs;
+
+	/* optimistically update recv_cnt.  if receiving fails below,
+	 * we disconnect anyways, and counters will be reset. */
+	mdev->recv_cnt += data_size>>9;
+
+	bio = req->master_bio;
+	D_ASSERT(sector == bio->bi_sector);
+
+	bio_for_each_segment(bvec, bio, i) {
+		expect = min_t(int, data_size, bvec->bv_len);
+		rr = drbd_recv(mdev,
+			     kmap(bvec->bv_page)+bvec->bv_offset,
+			     expect);
+		kunmap(bvec->bv_page);
+		if (rr != expect) {
+			dev_warn(DEV, "short read receiving data reply: "
+			     "read %d expected %d\n",
+			     rr, expect);
+			return 0;
+		}
+		data_size -= rr;
+	}
+
+	if (dgs) {
+		drbd_csum(mdev, mdev->integrity_r_tfm, bio, dig_vv);
+		if (memcmp(dig_in, dig_vv, dgs)) {
+			dev_err(DEV, "Digest integrity check FAILED. Broken NICs?\n");
+			return 0;
+		}
+	}
+
+	D_ASSERT(data_size == 0);
+	return 1;
+}
+
+/* e_end_resync_block() is called via
+ * drbd_process_done_ee() by asender only */
+static int e_end_resync_block(struct drbd_conf *mdev, struct drbd_work *w, int unused)
+{
+	struct drbd_epoch_entry *e = (struct drbd_epoch_entry *)w;
+	sector_t sector = e->sector;
+	int ok;
+
+	D_ASSERT(hlist_unhashed(&e->colision));
+
+	if (likely(drbd_bio_uptodate(e->private_bio))) {
+		drbd_set_in_sync(mdev, sector, e->size);
+		ok = drbd_send_ack(mdev, P_RS_WRITE_ACK, e);
+	} else {
+		/* Record failure to sync */
+		drbd_rs_failed_io(mdev, sector, e->size);
+
+		ok  = drbd_send_ack(mdev, P_NEG_ACK, e);
+	}
+	dec_unacked(mdev);
+
+	return ok;
+}
+
+static int recv_resync_read(struct drbd_conf *mdev, sector_t sector, int data_size) __releases(local)
+{
+	struct drbd_epoch_entry *e;
+
+	e = read_in_block(mdev, ID_SYNCER, sector, data_size);
+	if (!e) {
+		put_ldev(mdev);
+		return FALSE;
+	}
+
+	dec_rs_pending(mdev);
+
+	e->private_bio->bi_end_io = drbd_endio_write_sec;
+	e->private_bio->bi_rw = WRITE;
+	e->w.cb = e_end_resync_block;
+
+	inc_unacked(mdev);
+	/* corresponding dec_unacked() in e_end_resync_block()
+	 * respective _drbd_clear_done_ee */
+
+	spin_lock_irq(&mdev->req_lock);
+	list_add(&e->w.list, &mdev->sync_ee);
+	spin_unlock_irq(&mdev->req_lock);
+
+	trace_drbd_ee(mdev, e, "submitting for (rs)write");
+	trace_drbd_bio(mdev, "Sec", e->private_bio, 0, NULL);
+	drbd_generic_make_request(mdev, DRBD_FAULT_RS_WR, e->private_bio);
+	/* accounting done in endio */
+
+	maybe_kick_lo(mdev);
+	return TRUE;
+}
+
+static int receive_DataReply(struct drbd_conf *mdev, struct p_header *h)
+{
+	struct drbd_request *req;
+	sector_t sector;
+	unsigned int header_size, data_size;
+	int ok;
+	struct p_data *p = (struct p_data *)h;
+
+	header_size = sizeof(*p) - sizeof(*h);
+	data_size   = h->length  - header_size;
+
+	ERR_IF(data_size == 0) return FALSE;
+
+	if (drbd_recv(mdev, h->payload, header_size) != header_size)
+		return FALSE;
+
+	sector = be64_to_cpu(p->sector);
+
+	spin_lock_irq(&mdev->req_lock);
+	req = _ar_id_to_req(mdev, p->block_id, sector);
+	spin_unlock_irq(&mdev->req_lock);
+	if (unlikely(!req)) {
+		dev_err(DEV, "Got a corrupt block_id/sector pair(1).\n");
+		return FALSE;
+	}
+
+	/* hlist_del(&req->colision) is done in _req_may_be_done, to avoid
+	 * special casing it there for the various failure cases.
+	 * still no race with drbd_fail_pending_reads */
+	ok = recv_dless_read(mdev, req, sector, data_size);
+
+	if (ok)
+		req_mod(req, data_received);
+	/* else: nothing. handled from drbd_disconnect...
+	 * I don't think we may complete this just yet
+	 * in case we are "on-disconnect: freeze" */
+
+	return ok;
+}
+
+static int receive_RSDataReply(struct drbd_conf *mdev, struct p_header *h)
+{
+	sector_t sector;
+	unsigned int header_size, data_size;
+	int ok;
+	struct p_data *p = (struct p_data *)h;
+
+	header_size = sizeof(*p) - sizeof(*h);
+	data_size   = h->length  - header_size;
+
+	ERR_IF(data_size == 0) return FALSE;
+
+	if (drbd_recv(mdev, h->payload, header_size) != header_size)
+		return FALSE;
+
+	sector = be64_to_cpu(p->sector);
+	D_ASSERT(p->block_id == ID_SYNCER);
+
+	if (get_ldev(mdev)) {
+		/* data is submitted to disk within recv_resync_read.
+		 * corresponding put_ldev done below on error,
+		 * or in drbd_endio_write_sec. */
+		ok = recv_resync_read(mdev, sector, data_size);
+	} else {
+		if (__ratelimit(&drbd_ratelimit_state))
+			dev_err(DEV, "Can not write resync data to local disk.\n");
+
+		ok = drbd_drain_block(mdev, data_size);
+
+		drbd_send_ack_dp(mdev, P_NEG_ACK, p);
+	}
+
+	return ok;
+}
+
+/* e_end_block() is called via drbd_process_done_ee().
+ * this means this function only runs in the asender thread
+ */
+static int e_end_block(struct drbd_conf *mdev, struct drbd_work *w, int cancel)
+{
+	struct drbd_epoch_entry *e = (struct drbd_epoch_entry *)w;
+	sector_t sector = e->sector;
+	struct drbd_epoch *epoch;
+	int ok = 1, pcmd;
+
+	if (e->flags & EE_IS_BARRIER) {
+		epoch = previous_epoch(mdev, e->epoch);
+		if (epoch)
+			drbd_may_finish_epoch(mdev, epoch, EV_BARRIER_DONE + (cancel ? EV_CLEANUP : 0));
+	}
+
+	if (mdev->net_conf->wire_protocol == DRBD_PROT_C) {
+		if (likely(drbd_bio_uptodate(e->private_bio))) {
+			pcmd = (mdev->state.conn >= C_SYNC_SOURCE &&
+				mdev->state.conn <= C_PAUSED_SYNC_T &&
+				e->flags & EE_MAY_SET_IN_SYNC) ?
+				P_RS_WRITE_ACK : P_WRITE_ACK;
+			ok &= drbd_send_ack(mdev, pcmd, e);
+			if (pcmd == P_RS_WRITE_ACK)
+				drbd_set_in_sync(mdev, sector, e->size);
+		} else {
+			ok  = drbd_send_ack(mdev, P_NEG_ACK, e);
+			/* we expect it to be marked out of sync anyways...
+			 * maybe assert this?  */
+		}
+		dec_unacked(mdev);
+	}
+	/* we delete from the conflict detection hash _after_ we sent out the
+	 * P_WRITE_ACK / P_NEG_ACK, to get the sequence number right.  */
+	if (mdev->net_conf->two_primaries) {
+		spin_lock_irq(&mdev->req_lock);
+		D_ASSERT(!hlist_unhashed(&e->colision));
+		hlist_del_init(&e->colision);
+		spin_unlock_irq(&mdev->req_lock);
+	} else {
+		D_ASSERT(hlist_unhashed(&e->colision));
+	}
+
+	drbd_may_finish_epoch(mdev, e->epoch, EV_PUT + (cancel ? EV_CLEANUP : 0));
+
+	return ok;
+}
+
+static int e_send_discard_ack(struct drbd_conf *mdev, struct drbd_work *w, int unused)
+{
+	struct drbd_epoch_entry *e = (struct drbd_epoch_entry *)w;
+	int ok = 1;
+
+	D_ASSERT(mdev->net_conf->wire_protocol == DRBD_PROT_C);
+	ok = drbd_send_ack(mdev, P_DISCARD_ACK, e);
+
+	spin_lock_irq(&mdev->req_lock);
+	D_ASSERT(!hlist_unhashed(&e->colision));
+	hlist_del_init(&e->colision);
+	spin_unlock_irq(&mdev->req_lock);
+
+	dec_unacked(mdev);
+
+	return ok;
+}
+
+/* Called from receive_Data.
+ * Synchronize packets on sock with packets on msock.
+ *
+ * This is here so even when a P_DATA packet traveling via sock overtook an Ack
+ * packet traveling on msock, they are still processed in the order they have
+ * been sent.
+ *
+ * Note: we don't care for Ack packets overtaking P_DATA packets.
+ *
+ * In case packet_seq is larger than mdev->peer_seq number, there are
+ * outstanding packets on the msock. We wait for them to arrive.
+ * In case we are the logically next packet, we update mdev->peer_seq
+ * ourselves. Correctly handles 32bit wrap around.
+ *
+ * Assume we have a 10 GBit connection, that is about 1<<30 byte per second,
+ * about 1<<21 sectors per second. So "worst" case, we have 1<<3 == 8 seconds
+ * for the 24bit wrap (historical atomic_t guarantee on some archs), and we have
+ * 1<<9 == 512 seconds aka ages for the 32bit wrap around...
+ *
+ * returns 0 if we may process the packet,
+ * -ERESTARTSYS if we were interrupted (by disconnect signal). */
+static int drbd_wait_peer_seq(struct drbd_conf *mdev, const u32 packet_seq)
+{
+	DEFINE_WAIT(wait);
+	unsigned int p_seq;
+	long timeout;
+	int ret = 0;
+	spin_lock(&mdev->peer_seq_lock);
+	for (;;) {
+		prepare_to_wait(&mdev->seq_wait, &wait, TASK_INTERRUPTIBLE);
+		if (seq_le(packet_seq, mdev->peer_seq+1))
+			break;
+		if (signal_pending(current)) {
+			ret = -ERESTARTSYS;
+			break;
+		}
+		p_seq = mdev->peer_seq;
+		spin_unlock(&mdev->peer_seq_lock);
+		timeout = schedule_timeout(30*HZ);
+		spin_lock(&mdev->peer_seq_lock);
+		if (timeout == 0 && p_seq == mdev->peer_seq) {
+			ret = -ETIMEDOUT;
+			dev_err(DEV, "ASSERT FAILED waited 30 seconds for sequence update, forcing reconnect\n");
+			break;
+		}
+	}
+	finish_wait(&mdev->seq_wait, &wait);
+	if (mdev->peer_seq+1 == packet_seq)
+		mdev->peer_seq++;
+	spin_unlock(&mdev->peer_seq_lock);
+	return ret;
+}
+
+/* mirrored write */
+static int receive_Data(struct drbd_conf *mdev, struct p_header *h)
+{
+	sector_t sector;
+	struct drbd_epoch_entry *e;
+	struct p_data *p = (struct p_data *)h;
+	int header_size, data_size;
+	int rw = WRITE;
+	u32 dp_flags;
+
+	header_size = sizeof(*p) - sizeof(*h);
+	data_size   = h->length  - header_size;
+
+	ERR_IF(data_size == 0) return FALSE;
+
+	if (drbd_recv(mdev, h->payload, header_size) != header_size)
+		return FALSE;
+
+	if (!get_ldev(mdev)) {
+		if (__ratelimit(&drbd_ratelimit_state))
+			dev_err(DEV, "Can not write mirrored data block "
+			    "to local disk.\n");
+		spin_lock(&mdev->peer_seq_lock);
+		if (mdev->peer_seq+1 == be32_to_cpu(p->seq_num))
+			mdev->peer_seq++;
+		spin_unlock(&mdev->peer_seq_lock);
+
+		drbd_send_ack_dp(mdev, P_NEG_ACK, p);
+		atomic_inc(&mdev->current_epoch->epoch_size);
+		return drbd_drain_block(mdev, data_size);
+	}
+
+	/* get_ldev(mdev) successful.
+	 * Corresponding put_ldev done either below (on various errors),
+	 * or in drbd_endio_write_sec, if we successfully submit the data at
+	 * the end of this function. */
+
+	sector = be64_to_cpu(p->sector);
+	e = read_in_block(mdev, p->block_id, sector, data_size);
+	if (!e) {
+		put_ldev(mdev);
+		return FALSE;
+	}
+
+	e->private_bio->bi_end_io = drbd_endio_write_sec;
+	e->w.cb = e_end_block;
+
+	spin_lock(&mdev->epoch_lock);
+	e->epoch = mdev->current_epoch;
+	atomic_inc(&e->epoch->epoch_size);
+	atomic_inc(&e->epoch->active);
+
+	if (mdev->write_ordering == WO_bio_barrier && atomic_read(&e->epoch->epoch_size) == 1) {
+		struct drbd_epoch *epoch;
+		/* Issue a barrier if we start a new epoch, and the previous epoch
+		   was not a epoch containing a single request which already was
+		   a Barrier. */
+		epoch = list_entry(e->epoch->list.prev, struct drbd_epoch, list);
+		if (epoch == e->epoch) {
+			set_bit(DE_CONTAINS_A_BARRIER, &e->epoch->flags);
+			trace_drbd_epoch(mdev, e->epoch, EV_TRACE_ADD_BARRIER);
+			rw |= (1<<BIO_RW_BARRIER);
+			e->flags |= EE_IS_BARRIER;
+		} else {
+			if (atomic_read(&epoch->epoch_size) > 1 ||
+			    !test_bit(DE_CONTAINS_A_BARRIER, &epoch->flags)) {
+				set_bit(DE_BARRIER_IN_NEXT_EPOCH_ISSUED, &epoch->flags);
+				trace_drbd_epoch(mdev, epoch, EV_TRACE_SETTING_BI);
+				set_bit(DE_CONTAINS_A_BARRIER, &e->epoch->flags);
+				trace_drbd_epoch(mdev, e->epoch, EV_TRACE_ADD_BARRIER);
+				rw |= (1<<BIO_RW_BARRIER);
+				e->flags |= EE_IS_BARRIER;
+			}
+		}
+	}
+	spin_unlock(&mdev->epoch_lock);
+
+	dp_flags = be32_to_cpu(p->dp_flags);
+	if (dp_flags & DP_HARDBARRIER) {
+		dev_err(DEV, "ASSERT FAILED would have submitted barrier request\n");
+		/* rw |= (1<<BIO_RW_BARRIER); */
+	}
+	if (dp_flags & DP_RW_SYNC)
+		rw |= (1<<BIO_RW_SYNCIO) | (1<<BIO_RW_UNPLUG);
+	if (dp_flags & DP_MAY_SET_IN_SYNC)
+		e->flags |= EE_MAY_SET_IN_SYNC;
+
+	/* I'm the receiver, I do hold a net_cnt reference. */
+	if (!mdev->net_conf->two_primaries) {
+		spin_lock_irq(&mdev->req_lock);
+	} else {
+		/* don't get the req_lock yet,
+		 * we may sleep in drbd_wait_peer_seq */
+		const int size = e->size;
+		const int discard = test_bit(DISCARD_CONCURRENT, &mdev->flags);
+		DEFINE_WAIT(wait);
+		struct drbd_request *i;
+		struct hlist_node *n;
+		struct hlist_head *slot;
+		int first;
+
+		D_ASSERT(mdev->net_conf->wire_protocol == DRBD_PROT_C);
+		BUG_ON(mdev->ee_hash == NULL);
+		BUG_ON(mdev->tl_hash == NULL);
+
+		/* conflict detection and handling:
+		 * 1. wait on the sequence number,
+		 *    in case this data packet overtook ACK packets.
+		 * 2. check our hash tables for conflicting requests.
+		 *    we only need to walk the tl_hash, since an ee can not
+		 *    have a conflict with an other ee: on the submitting
+		 *    node, the corresponding req had already been conflicting,
+		 *    and a conflicting req is never sent.
+		 *
+		 * Note: for two_primaries, we are protocol C,
+		 * so there cannot be any request that is DONE
+		 * but still on the transfer log.
+		 *
+		 * unconditionally add to the ee_hash.
+		 *
+		 * if no conflicting request is found:
+		 *    submit.
+		 *
+		 * if any conflicting request is found
+		 * that has not yet been acked,
+		 * AND I have the "discard concurrent writes" flag:
+		 *	 queue (via done_ee) the P_DISCARD_ACK; OUT.
+		 *
+		 * if any conflicting request is found:
+		 *	 block the receiver, waiting on misc_wait
+		 *	 until no more conflicting requests are there,
+		 *	 or we get interrupted (disconnect).
+		 *
+		 *	 we do not just write after local io completion of those
+		 *	 requests, but only after req is done completely, i.e.
+		 *	 we wait for the P_DISCARD_ACK to arrive!
+		 *
+		 *	 then proceed normally, i.e. submit.
+		 */
+		if (drbd_wait_peer_seq(mdev, be32_to_cpu(p->seq_num)))
+			goto out_interrupted;
+
+		spin_lock_irq(&mdev->req_lock);
+
+		hlist_add_head(&e->colision, ee_hash_slot(mdev, sector));
+
+#define OVERLAPS overlaps(i->sector, i->size, sector, size)
+		slot = tl_hash_slot(mdev, sector);
+		first = 1;
+		for (;;) {
+			int have_unacked = 0;
+			int have_conflict = 0;
+			prepare_to_wait(&mdev->misc_wait, &wait,
+				TASK_INTERRUPTIBLE);
+			hlist_for_each_entry(i, n, slot, colision) {
+				if (OVERLAPS) {
+					/* only ALERT on first iteration,
+					 * we may be woken up early... */
+					if (first)
+						dev_alert(DEV, "%s[%u] Concurrent local write detected!"
+						      "	new: %llus +%u; pending: %llus +%u\n",
+						      current->comm, current->pid,
+						      (unsigned long long)sector, size,
+						      (unsigned long long)i->sector, i->size);
+					if (i->rq_state & RQ_NET_PENDING)
+						++have_unacked;
+					++have_conflict;
+				}
+			}
+#undef OVERLAPS
+			if (!have_conflict)
+				break;
+
+			/* Discard Ack only for the _first_ iteration */
+			if (first && discard && have_unacked) {
+				dev_alert(DEV, "Concurrent write! [DISCARD BY FLAG] sec=%llus\n",
+				     (unsigned long long)sector);
+				inc_unacked(mdev);
+				e->w.cb = e_send_discard_ack;
+				list_add_tail(&e->w.list, &mdev->done_ee);
+
+				spin_unlock_irq(&mdev->req_lock);
+
+				/* we could probably send that P_DISCARD_ACK ourselves,
+				 * but I don't like the receiver using the msock */
+
+				put_ldev(mdev);
+				wake_asender(mdev);
+				finish_wait(&mdev->misc_wait, &wait);
+				return TRUE;
+			}
+
+			if (signal_pending(current)) {
+				hlist_del_init(&e->colision);
+
+				spin_unlock_irq(&mdev->req_lock);
+
+				finish_wait(&mdev->misc_wait, &wait);
+				goto out_interrupted;
+			}
+
+			spin_unlock_irq(&mdev->req_lock);
+			if (first) {
+				first = 0;
+				dev_alert(DEV, "Concurrent write! [W AFTERWARDS] "
+				     "sec=%llus\n", (unsigned long long)sector);
+			} else if (discard) {
+				/* we had none on the first iteration.
+				 * there must be none now. */
+				D_ASSERT(have_unacked == 0);
+			}
+			schedule();
+			spin_lock_irq(&mdev->req_lock);
+		}
+		finish_wait(&mdev->misc_wait, &wait);
+	}
+
+	list_add(&e->w.list, &mdev->active_ee);
+	spin_unlock_irq(&mdev->req_lock);
+
+	switch (mdev->net_conf->wire_protocol) {
+	case DRBD_PROT_C:
+		inc_unacked(mdev);
+		/* corresponding dec_unacked() in e_end_block()
+		 * respective _drbd_clear_done_ee */
+		break;
+	case DRBD_PROT_B:
+		/* I really don't like it that the receiver thread
+		 * sends on the msock, but anyways */
+		drbd_send_ack(mdev, P_RECV_ACK, e);
+		break;
+	case DRBD_PROT_A:
+		/* nothing to do */
+		break;
+	}
+
+	if (mdev->state.pdsk == D_DISKLESS) {
+		/* In case we have the only disk of the cluster, */
+		drbd_set_out_of_sync(mdev, e->sector, e->size);
+		e->flags |= EE_CALL_AL_COMPLETE_IO;
+		drbd_al_begin_io(mdev, e->sector);
+	}
+
+	e->private_bio->bi_rw = rw;
+	trace_drbd_ee(mdev, e, "submitting for (data)write");
+	trace_drbd_bio(mdev, "Sec", e->private_bio, 0, NULL);
+	drbd_generic_make_request(mdev, DRBD_FAULT_DT_WR, e->private_bio);
+	/* accounting done in endio */
+
+	maybe_kick_lo(mdev);
+	return TRUE;
+
+out_interrupted:
+	/* yes, the epoch_size now is imbalanced.
+	 * but we drop the connection anyways, so we don't have a chance to
+	 * receive a barrier... atomic_inc(&mdev->epoch_size); */
+	put_ldev(mdev);
+	drbd_free_ee(mdev, e);
+	return FALSE;
+}
+
+static int receive_DataRequest(struct drbd_conf *mdev, struct p_header *h)
+{
+	sector_t sector;
+	const sector_t capacity = drbd_get_capacity(mdev->this_bdev);
+	struct drbd_epoch_entry *e;
+	struct digest_info *di = NULL;
+	int size, digest_size;
+	unsigned int fault_type;
+	struct p_block_req *p =
+		(struct p_block_req *)h;
+	const int brps = sizeof(*p)-sizeof(*h);
+
+	if (drbd_recv(mdev, h->payload, brps) != brps)
+		return FALSE;
+
+	sector = be64_to_cpu(p->sector);
+	size   = be32_to_cpu(p->blksize);
+
+	if (size <= 0 || (size & 0x1ff) != 0 || size > DRBD_MAX_SEGMENT_SIZE) {
+		dev_err(DEV, "%s:%d: sector: %llus, size: %u\n", __FILE__, __LINE__,
+				(unsigned long long)sector, size);
+		return FALSE;
+	}
+	if (sector + (size>>9) > capacity) {
+		dev_err(DEV, "%s:%d: sector: %llus, size: %u\n", __FILE__, __LINE__,
+				(unsigned long long)sector, size);
+		return FALSE;
+	}
+
+	if (!get_ldev_if_state(mdev, D_UP_TO_DATE)) {
+		if (__ratelimit(&drbd_ratelimit_state))
+			dev_err(DEV, "Can not satisfy peer's read request, "
+			    "no local data.\n");
+		drbd_send_ack_rp(mdev, h->command == P_DATA_REQUEST ? P_NEG_DREPLY :
+				 P_NEG_RS_DREPLY , p);
+		return TRUE;
+	}
+
+	/* GFP_NOIO, because we must not cause arbitrary write-out: in a DRBD
+	 * "criss-cross" setup, that might cause write-out on some other DRBD,
+	 * which in turn might block on the other node at this very place.  */
+	e = drbd_alloc_ee(mdev, p->block_id, sector, size, GFP_NOIO);
+	if (!e) {
+		put_ldev(mdev);
+		return FALSE;
+	}
+
+	e->private_bio->bi_rw = READ;
+	e->private_bio->bi_end_io = drbd_endio_read_sec;
+
+	switch (h->command) {
+	case P_DATA_REQUEST:
+		e->w.cb = w_e_end_data_req;
+		fault_type = DRBD_FAULT_DT_RD;
+		break;
+	case P_RS_DATA_REQUEST:
+		e->w.cb = w_e_end_rsdata_req;
+		fault_type = DRBD_FAULT_RS_RD;
+		/* Eventually this should become asynchronously. Currently it
+		 * blocks the whole receiver just to delay the reading of a
+		 * resync data block.
+		 * the drbd_work_queue mechanism is made for this...
+		 */
+		if (!drbd_rs_begin_io(mdev, sector)) {
+			/* we have been interrupted,
+			 * probably connection lost! */
+			D_ASSERT(signal_pending(current));
+			goto out_free_e;
+		}
+		break;
+
+	case P_OV_REPLY:
+	case P_CSUM_RS_REQUEST:
+		fault_type = DRBD_FAULT_RS_RD;
+		digest_size = h->length - brps ;
+		di = kmalloc(sizeof(*di) + digest_size, GFP_NOIO);
+		if (!di)
+			goto out_free_e;
+
+		di->digest_size = digest_size;
+		di->digest = (((char *)di)+sizeof(struct digest_info));
+
+		if (drbd_recv(mdev, di->digest, digest_size) != digest_size)
+			goto out_free_e;
+
+		e->block_id = (u64)(unsigned long)di;
+		if (h->command == P_CSUM_RS_REQUEST) {
+			D_ASSERT(mdev->agreed_pro_version >= 89);
+			e->w.cb = w_e_end_csum_rs_req;
+		} else if (h->command == P_OV_REPLY) {
+			e->w.cb = w_e_end_ov_reply;
+			dec_rs_pending(mdev);
+			break;
+		}
+
+		if (!drbd_rs_begin_io(mdev, sector)) {
+			/* we have been interrupted, probably connection lost! */
+			D_ASSERT(signal_pending(current));
+			goto out_free_e;
+		}
+		break;
+
+	case P_OV_REQUEST:
+		if (mdev->state.conn >= C_CONNECTED &&
+		    mdev->state.conn != C_VERIFY_T)
+			dev_warn(DEV, "ASSERT FAILED: got P_OV_REQUEST while being %s\n",
+				drbd_conn_str(mdev->state.conn));
+		if (mdev->ov_start_sector == ~(sector_t)0 &&
+		    mdev->agreed_pro_version >= 90) {
+			mdev->ov_start_sector = sector;
+			mdev->ov_position = sector;
+			mdev->ov_left = mdev->rs_total - BM_SECT_TO_BIT(sector);
+			dev_info(DEV, "Online Verify start sector: %llu\n",
+					(unsigned long long)sector);
+		}
+		e->w.cb = w_e_end_ov_req;
+		fault_type = DRBD_FAULT_RS_RD;
+		/* Eventually this should become asynchronous. Currently it
+		 * blocks the whole receiver just to delay the reading of a
+		 * resync data block.
+		 * the drbd_work_queue mechanism is made for this...
+		 */
+		if (!drbd_rs_begin_io(mdev, sector)) {
+			/* we have been interrupted,
+			 * probably connection lost! */
+			D_ASSERT(signal_pending(current));
+			goto out_free_e;
+		}
+		break;
+
+
+	default:
+		dev_err(DEV, "unexpected command (%s) in receive_DataRequest\n",
+		    cmdname(h->command));
+		fault_type = DRBD_FAULT_MAX;
+	}
+
+	spin_lock_irq(&mdev->req_lock);
+	list_add(&e->w.list, &mdev->read_ee);
+	spin_unlock_irq(&mdev->req_lock);
+
+	inc_unacked(mdev);
+
+	trace_drbd_ee(mdev, e, "submitting for read");
+	trace_drbd_bio(mdev, "Sec", e->private_bio, 0, NULL);
+	drbd_generic_make_request(mdev, fault_type, e->private_bio);
+	maybe_kick_lo(mdev);
+
+	return TRUE;
+
+out_free_e:
+	kfree(di);
+	put_ldev(mdev);
+	drbd_free_ee(mdev, e);
+	return FALSE;
+}
+
+static int drbd_asb_recover_0p(struct drbd_conf *mdev) __must_hold(local)
+{
+	int self, peer, rv = -100;
+	unsigned long ch_self, ch_peer;
+
+	self = mdev->ldev->md.uuid[UI_BITMAP] & 1;
+	peer = mdev->p_uuid[UI_BITMAP] & 1;
+
+	ch_peer = mdev->p_uuid[UI_SIZE];
+	ch_self = mdev->comm_bm_set;
+
+	switch (mdev->net_conf->after_sb_0p) {
+	case ASB_CONSENSUS:
+	case ASB_DISCARD_SECONDARY:
+	case ASB_CALL_HELPER:
+		dev_err(DEV, "Configuration error.\n");
+		break;
+	case ASB_DISCONNECT:
+		break;
+	case ASB_DISCARD_YOUNGER_PRI:
+		if (self == 0 && peer == 1) {
+			rv = -1;
+			break;
+		}
+		if (self == 1 && peer == 0) {
+			rv =  1;
+			break;
+		}
+		/* Else fall through to one of the other strategies... */
+	case ASB_DISCARD_OLDER_PRI:
+		if (self == 0 && peer == 1) {
+			rv = 1;
+			break;
+		}
+		if (self == 1 && peer == 0) {
+			rv = -1;
+			break;
+		}
+		/* Else fall through to one of the other strategies... */
+		dev_warn(DEV, "Discard younger/older primary did not found a decision\n"
+		     "Using discard-least-changes instead\n");
+	case ASB_DISCARD_ZERO_CHG:
+		if (ch_peer == 0 && ch_self == 0) {
+			rv = test_bit(DISCARD_CONCURRENT, &mdev->flags)
+				? -1 : 1;
+			break;
+		} else {
+			if (ch_peer == 0) { rv =  1; break; }
+			if (ch_self == 0) { rv = -1; break; }
+		}
+		if (mdev->net_conf->after_sb_0p == ASB_DISCARD_ZERO_CHG)
+			break;
+	case ASB_DISCARD_LEAST_CHG:
+		if	(ch_self < ch_peer)
+			rv = -1;
+		else if (ch_self > ch_peer)
+			rv =  1;
+		else /* ( ch_self == ch_peer ) */
+		     /* Well, then use something else. */
+			rv = test_bit(DISCARD_CONCURRENT, &mdev->flags)
+				? -1 : 1;
+		break;
+	case ASB_DISCARD_LOCAL:
+		rv = -1;
+		break;
+	case ASB_DISCARD_REMOTE:
+		rv =  1;
+	}
+
+	return rv;
+}
+
+static int drbd_asb_recover_1p(struct drbd_conf *mdev) __must_hold(local)
+{
+	int self, peer, hg, rv = -100;
+
+	self = mdev->ldev->md.uuid[UI_BITMAP] & 1;
+	peer = mdev->p_uuid[UI_BITMAP] & 1;
+
+	switch (mdev->net_conf->after_sb_1p) {
+	case ASB_DISCARD_YOUNGER_PRI:
+	case ASB_DISCARD_OLDER_PRI:
+	case ASB_DISCARD_LEAST_CHG:
+	case ASB_DISCARD_LOCAL:
+	case ASB_DISCARD_REMOTE:
+		dev_err(DEV, "Configuration error.\n");
+		break;
+	case ASB_DISCONNECT:
+		break;
+	case ASB_CONSENSUS:
+		hg = drbd_asb_recover_0p(mdev);
+		if (hg == -1 && mdev->state.role == R_SECONDARY)
+			rv = hg;
+		if (hg == 1  && mdev->state.role == R_PRIMARY)
+			rv = hg;
+		break;
+	case ASB_VIOLENTLY:
+		rv = drbd_asb_recover_0p(mdev);
+		break;
+	case ASB_DISCARD_SECONDARY:
+		return mdev->state.role == R_PRIMARY ? 1 : -1;
+	case ASB_CALL_HELPER:
+		hg = drbd_asb_recover_0p(mdev);
+		if (hg == -1 && mdev->state.role == R_PRIMARY) {
+			self = drbd_set_role(mdev, R_SECONDARY, 0);
+			 /* drbd_change_state() does not sleep while in SS_IN_TRANSIENT_STATE,
+			  * we might be here in C_WF_REPORT_PARAMS which is transient.
+			  * we do not need to wait for the after state change work either. */
+			self = drbd_change_state(mdev, CS_VERBOSE, NS(role, R_SECONDARY));
+			if (self != SS_SUCCESS) {
+				drbd_khelper(mdev, "pri-lost-after-sb");
+			} else {
+				dev_warn(DEV, "Successfully gave up primary role.\n");
+				rv = hg;
+			}
+		} else
+			rv = hg;
+	}
+
+	return rv;
+}
+
+static int drbd_asb_recover_2p(struct drbd_conf *mdev) __must_hold(local)
+{
+	int self, peer, hg, rv = -100;
+
+	self = mdev->ldev->md.uuid[UI_BITMAP] & 1;
+	peer = mdev->p_uuid[UI_BITMAP] & 1;
+
+	switch (mdev->net_conf->after_sb_2p) {
+	case ASB_DISCARD_YOUNGER_PRI:
+	case ASB_DISCARD_OLDER_PRI:
+	case ASB_DISCARD_LEAST_CHG:
+	case ASB_DISCARD_LOCAL:
+	case ASB_DISCARD_REMOTE:
+	case ASB_CONSENSUS:
+	case ASB_DISCARD_SECONDARY:
+		dev_err(DEV, "Configuration error.\n");
+		break;
+	case ASB_VIOLENTLY:
+		rv = drbd_asb_recover_0p(mdev);
+		break;
+	case ASB_DISCONNECT:
+		break;
+	case ASB_CALL_HELPER:
+		hg = drbd_asb_recover_0p(mdev);
+		if (hg == -1) {
+			 /* drbd_change_state() does not sleep while in SS_IN_TRANSIENT_STATE,
+			  * we might be here in C_WF_REPORT_PARAMS which is transient.
+			  * we do not need to wait for the after state change work either. */
+			self = drbd_change_state(mdev, CS_VERBOSE, NS(role, R_SECONDARY));
+			if (self != SS_SUCCESS) {
+				drbd_khelper(mdev, "pri-lost-after-sb");
+			} else {
+				dev_warn(DEV, "Successfully gave up primary role.\n");
+				rv = hg;
+			}
+		} else
+			rv = hg;
+	}
+
+	return rv;
+}
+
+static void drbd_uuid_dump(struct drbd_conf *mdev, char *text, u64 *uuid,
+			   u64 bits, u64 flags)
+{
+	if (!uuid) {
+		dev_info(DEV, "%s uuid info vanished while I was looking!\n", text);
+		return;
+	}
+	dev_info(DEV, "%s %016llX:%016llX:%016llX:%016llX bits:%llu flags:%llX\n",
+	     text,
+	     (unsigned long long)uuid[UI_CURRENT],
+	     (unsigned long long)uuid[UI_BITMAP],
+	     (unsigned long long)uuid[UI_HISTORY_START],
+	     (unsigned long long)uuid[UI_HISTORY_END],
+	     (unsigned long long)bits,
+	     (unsigned long long)flags);
+}
+
+/*
+  100	after split brain try auto recover
+    2	C_SYNC_SOURCE set BitMap
+    1	C_SYNC_SOURCE use BitMap
+    0	no Sync
+   -1	C_SYNC_TARGET use BitMap
+   -2	C_SYNC_TARGET set BitMap
+ -100	after split brain, disconnect
+-1000	unrelated data
+ */
+static int drbd_uuid_compare(struct drbd_conf *mdev, int *rule_nr) __must_hold(local)
+{
+	u64 self, peer;
+	int i, j;
+
+	self = mdev->ldev->md.uuid[UI_CURRENT] & ~((u64)1);
+	peer = mdev->p_uuid[UI_CURRENT] & ~((u64)1);
+
+	*rule_nr = 10;
+	if (self == UUID_JUST_CREATED && peer == UUID_JUST_CREATED)
+		return 0;
+
+	*rule_nr = 20;
+	if ((self == UUID_JUST_CREATED || self == (u64)0) &&
+	     peer != UUID_JUST_CREATED)
+		return -2;
+
+	*rule_nr = 30;
+	if (self != UUID_JUST_CREATED &&
+	    (peer == UUID_JUST_CREATED || peer == (u64)0))
+		return 2;
+
+	if (self == peer) {
+		int rct, dc; /* roles at crash time */
+
+		if (mdev->p_uuid[UI_BITMAP] == (u64)0 && mdev->ldev->md.uuid[UI_BITMAP] != (u64)0) {
+
+			if (mdev->agreed_pro_version < 91)
+				return -1001;
+
+			if ((mdev->ldev->md.uuid[UI_BITMAP] & ~((u64)1)) == (mdev->p_uuid[UI_HISTORY_START] & ~((u64)1)) &&
+			    (mdev->ldev->md.uuid[UI_HISTORY_START] & ~((u64)1)) == (mdev->p_uuid[UI_HISTORY_START + 1] & ~((u64)1))) {
+				dev_info(DEV, "was SyncSource, missed the resync finished event, corrected myself:\n");
+				drbd_uuid_set_bm(mdev, 0UL);
+
+				drbd_uuid_dump(mdev, "self", mdev->ldev->md.uuid,
+					       mdev->state.disk >= D_NEGOTIATING ? drbd_bm_total_weight(mdev) : 0, 0);
+				*rule_nr = 34;
+			} else {
+				dev_info(DEV, "was SyncSource (peer failed to write sync_uuid)\n");
+				*rule_nr = 36;
+			}
+
+			return 1;
+		}
+
+		if (mdev->ldev->md.uuid[UI_BITMAP] == (u64)0 && mdev->p_uuid[UI_BITMAP] != (u64)0) {
+
+			if (mdev->agreed_pro_version < 91)
+				return -1001;
+
+			if ((mdev->ldev->md.uuid[UI_HISTORY_START] & ~((u64)1)) == (mdev->p_uuid[UI_BITMAP] & ~((u64)1)) &&
+			    (mdev->ldev->md.uuid[UI_HISTORY_START + 1] & ~((u64)1)) == (mdev->p_uuid[UI_HISTORY_START] & ~((u64)1))) {
+				dev_info(DEV, "was SyncTarget, peer missed the resync finished event, corrected peer:\n");
+
+				mdev->p_uuid[UI_HISTORY_START + 1] = mdev->p_uuid[UI_HISTORY_START];
+				mdev->p_uuid[UI_HISTORY_START] = mdev->p_uuid[UI_BITMAP];
+				mdev->p_uuid[UI_BITMAP] = 0UL;
+
+				drbd_uuid_dump(mdev, "peer", mdev->p_uuid, mdev->p_uuid[UI_SIZE], mdev->p_uuid[UI_FLAGS]);
+				*rule_nr = 35;
+			} else {
+				dev_info(DEV, "was SyncTarget (failed to write sync_uuid)\n");
+				*rule_nr = 37;
+			}
+
+			return -1;
+		}
+
+		/* Common power [off|failure] */
+		rct = (test_bit(CRASHED_PRIMARY, &mdev->flags) ? 1 : 0) +
+			(mdev->p_uuid[UI_FLAGS] & 2);
+		/* lowest bit is set when we were primary,
+		 * next bit (weight 2) is set when peer was primary */
+		*rule_nr = 40;
+
+		switch (rct) {
+		case 0: /* !self_pri && !peer_pri */ return 0;
+		case 1: /*  self_pri && !peer_pri */ return 1;
+		case 2: /* !self_pri &&  peer_pri */ return -1;
+		case 3: /*  self_pri &&  peer_pri */
+			dc = test_bit(DISCARD_CONCURRENT, &mdev->flags);
+			return dc ? -1 : 1;
+		}
+	}
+
+	*rule_nr = 50;
+	peer = mdev->p_uuid[UI_BITMAP] & ~((u64)1);
+	if (self == peer)
+		return -1;
+
+	*rule_nr = 51;
+	peer = mdev->p_uuid[UI_HISTORY_START] & ~((u64)1);
+	if (self == peer) {
+		self = mdev->ldev->md.uuid[UI_HISTORY_START] & ~((u64)1);
+		peer = mdev->p_uuid[UI_HISTORY_START + 1] & ~((u64)1);
+		if (self == peer) {
+			/* The last P_SYNC_UUID did not get though. Undo the last start of
+			   resync as sync source modifications of the peer's UUIDs. */
+
+			if (mdev->agreed_pro_version < 91)
+				return -1001;
+
+			mdev->p_uuid[UI_BITMAP] = mdev->p_uuid[UI_HISTORY_START];
+			mdev->p_uuid[UI_HISTORY_START] = mdev->p_uuid[UI_HISTORY_START + 1];
+			return -1;
+		}
+	}
+
+	*rule_nr = 60;
+	self = mdev->ldev->md.uuid[UI_CURRENT] & ~((u64)1);
+	for (i = UI_HISTORY_START; i <= UI_HISTORY_END; i++) {
+		peer = mdev->p_uuid[i] & ~((u64)1);
+		if (self == peer)
+			return -2;
+	}
+
+	*rule_nr = 70;
+	self = mdev->ldev->md.uuid[UI_BITMAP] & ~((u64)1);
+	peer = mdev->p_uuid[UI_CURRENT] & ~((u64)1);
+	if (self == peer)
+		return 1;
+
+	*rule_nr = 71;
+	self = mdev->ldev->md.uuid[UI_HISTORY_START] & ~((u64)1);
+	if (self == peer) {
+		self = mdev->ldev->md.uuid[UI_HISTORY_START + 1] & ~((u64)1);
+		peer = mdev->p_uuid[UI_HISTORY_START] & ~((u64)1);
+		if (self == peer) {
+			/* The last P_SYNC_UUID did not get though. Undo the last start of
+			   resync as sync source modifications of our UUIDs. */
+
+			if (mdev->agreed_pro_version < 91)
+				return -1001;
+
+			_drbd_uuid_set(mdev, UI_BITMAP, mdev->ldev->md.uuid[UI_HISTORY_START]);
+			_drbd_uuid_set(mdev, UI_HISTORY_START, mdev->ldev->md.uuid[UI_HISTORY_START + 1]);
+
+			dev_info(DEV, "Undid last start of resync:\n");
+
+			drbd_uuid_dump(mdev, "self", mdev->ldev->md.uuid,
+				       mdev->state.disk >= D_NEGOTIATING ? drbd_bm_total_weight(mdev) : 0, 0);
+
+			return 1;
+		}
+	}
+
+
+	*rule_nr = 80;
+	for (i = UI_HISTORY_START; i <= UI_HISTORY_END; i++) {
+		self = mdev->ldev->md.uuid[i] & ~((u64)1);
+		if (self == peer)
+			return 2;
+	}
+
+	*rule_nr = 90;
+	self = mdev->ldev->md.uuid[UI_BITMAP] & ~((u64)1);
+	peer = mdev->p_uuid[UI_BITMAP] & ~((u64)1);
+	if (self == peer && self != ((u64)0))
+		return 100;
+
+	*rule_nr = 100;
+	for (i = UI_HISTORY_START; i <= UI_HISTORY_END; i++) {
+		self = mdev->ldev->md.uuid[i] & ~((u64)1);
+		for (j = UI_HISTORY_START; j <= UI_HISTORY_END; j++) {
+			peer = mdev->p_uuid[j] & ~((u64)1);
+			if (self == peer)
+				return -100;
+		}
+	}
+
+	return -1000;
+}
+
+/* drbd_sync_handshake() returns the new conn state on success, or
+   CONN_MASK (-1) on failure.
+ */
+static enum drbd_conns drbd_sync_handshake(struct drbd_conf *mdev, enum drbd_role peer_role,
+					   enum drbd_disk_state peer_disk) __must_hold(local)
+{
+	int hg, rule_nr;
+	enum drbd_conns rv = C_MASK;
+	enum drbd_disk_state mydisk;
+
+	mydisk = mdev->state.disk;
+	if (mydisk == D_NEGOTIATING)
+		mydisk = mdev->new_state_tmp.disk;
+
+	dev_info(DEV, "drbd_sync_handshake:\n");
+	drbd_uuid_dump(mdev, "self", mdev->ldev->md.uuid, mdev->comm_bm_set, 0);
+	drbd_uuid_dump(mdev, "peer", mdev->p_uuid,
+		       mdev->p_uuid[UI_SIZE], mdev->p_uuid[UI_FLAGS]);
+
+	hg = drbd_uuid_compare(mdev, &rule_nr);
+
+	dev_info(DEV, "uuid_compare()=%d by rule %d\n", hg, rule_nr);
+
+	if (hg == -1000) {
+		dev_alert(DEV, "Unrelated data, aborting!\n");
+		return C_MASK;
+	}
+	if (hg == -1001) {
+		dev_alert(DEV, "To resolve this both sides have to support at least protocol\n");
+		return C_MASK;
+	}
+
+	if    ((mydisk == D_INCONSISTENT && peer_disk > D_INCONSISTENT) ||
+	    (peer_disk == D_INCONSISTENT && mydisk    > D_INCONSISTENT)) {
+		int f = (hg == -100) || abs(hg) == 2;
+		hg = mydisk > D_INCONSISTENT ? 1 : -1;
+		if (f)
+			hg = hg*2;
+		dev_info(DEV, "Becoming sync %s due to disk states.\n",
+		     hg > 0 ? "source" : "target");
+	}
+
+	if (hg == 100 || (hg == -100 && mdev->net_conf->always_asbp)) {
+		int pcount = (mdev->state.role == R_PRIMARY)
+			   + (peer_role == R_PRIMARY);
+		int forced = (hg == -100);
+
+		switch (pcount) {
+		case 0:
+			hg = drbd_asb_recover_0p(mdev);
+			break;
+		case 1:
+			hg = drbd_asb_recover_1p(mdev);
+			break;
+		case 2:
+			hg = drbd_asb_recover_2p(mdev);
+			break;
+		}
+		if (abs(hg) < 100) {
+			dev_warn(DEV, "Split-Brain detected, %d primaries, "
+			     "automatically solved. Sync from %s node\n",
+			     pcount, (hg < 0) ? "peer" : "this");
+			if (forced) {
+				dev_warn(DEV, "Doing a full sync, since"
+				     " UUIDs where ambiguous.\n");
+				hg = hg*2;
+			}
+		}
+	}
+
+	if (hg == -100) {
+		if (mdev->net_conf->want_lose && !(mdev->p_uuid[UI_FLAGS]&1))
+			hg = -1;
+		if (!mdev->net_conf->want_lose && (mdev->p_uuid[UI_FLAGS]&1))
+			hg = 1;
+
+		if (abs(hg) < 100)
+			dev_warn(DEV, "Split-Brain detected, manually solved. "
+			     "Sync from %s node\n",
+			     (hg < 0) ? "peer" : "this");
+	}
+
+	if (hg == -100) {
+		dev_alert(DEV, "Split-Brain detected, dropping connection!\n");
+		drbd_khelper(mdev, "split-brain");
+		return C_MASK;
+	}
+
+	if (hg > 0 && mydisk <= D_INCONSISTENT) {
+		dev_err(DEV, "I shall become SyncSource, but I am inconsistent!\n");
+		return C_MASK;
+	}
+
+	if (hg < 0 && /* by intention we do not use mydisk here. */
+	    mdev->state.role == R_PRIMARY && mdev->state.disk >= D_CONSISTENT) {
+		switch (mdev->net_conf->rr_conflict) {
+		case ASB_CALL_HELPER:
+			drbd_khelper(mdev, "pri-lost");
+			/* fall through */
+		case ASB_DISCONNECT:
+			dev_err(DEV, "I shall become SyncTarget, but I am primary!\n");
+			return C_MASK;
+		case ASB_VIOLENTLY:
+			dev_warn(DEV, "Becoming SyncTarget, violating the stable-data"
+			     "assumption\n");
+		}
+	}
+
+	if (abs(hg) >= 2) {
+		dev_info(DEV, "Writing the whole bitmap, full sync required after drbd_sync_handshake.\n");
+		if (drbd_bitmap_io(mdev, &drbd_bmio_set_n_write, "set_n_write from sync_handshake"))
+			return C_MASK;
+	}
+
+	if (hg > 0) { /* become sync source. */
+		rv = C_WF_BITMAP_S;
+	} else if (hg < 0) { /* become sync target */
+		rv = C_WF_BITMAP_T;
+	} else {
+		rv = C_CONNECTED;
+		if (drbd_bm_total_weight(mdev)) {
+			dev_info(DEV, "No resync, but %lu bits in bitmap!\n",
+			     drbd_bm_total_weight(mdev));
+		}
+	}
+
+	return rv;
+}
+
+/* returns 1 if invalid */
+static int cmp_after_sb(enum drbd_after_sb_p peer, enum drbd_after_sb_p self)
+{
+	/* ASB_DISCARD_REMOTE - ASB_DISCARD_LOCAL is valid */
+	if ((peer == ASB_DISCARD_REMOTE && self == ASB_DISCARD_LOCAL) ||
+	    (self == ASB_DISCARD_REMOTE && peer == ASB_DISCARD_LOCAL))
+		return 0;
+
+	/* any other things with ASB_DISCARD_REMOTE or ASB_DISCARD_LOCAL are invalid */
+	if (peer == ASB_DISCARD_REMOTE || peer == ASB_DISCARD_LOCAL ||
+	    self == ASB_DISCARD_REMOTE || self == ASB_DISCARD_LOCAL)
+		return 1;
+
+	/* everything else is valid if they are equal on both sides. */
+	if (peer == self)
+		return 0;
+
+	/* everything es is invalid. */
+	return 1;
+}
+
+static int receive_protocol(struct drbd_conf *mdev, struct p_header *h)
+{
+	struct p_protocol *p = (struct p_protocol *)h;
+	int header_size, data_size;
+	int p_proto, p_after_sb_0p, p_after_sb_1p, p_after_sb_2p;
+	int p_want_lose, p_two_primaries;
+	char p_integrity_alg[SHARED_SECRET_MAX] = "";
+
+	header_size = sizeof(*p) - sizeof(*h);
+	data_size   = h->length  - header_size;
+
+	if (drbd_recv(mdev, h->payload, header_size) != header_size)
+		return FALSE;
+
+	p_proto		= be32_to_cpu(p->protocol);
+	p_after_sb_0p	= be32_to_cpu(p->after_sb_0p);
+	p_after_sb_1p	= be32_to_cpu(p->after_sb_1p);
+	p_after_sb_2p	= be32_to_cpu(p->after_sb_2p);
+	p_want_lose	= be32_to_cpu(p->want_lose);
+	p_two_primaries = be32_to_cpu(p->two_primaries);
+
+	if (p_proto != mdev->net_conf->wire_protocol) {
+		dev_err(DEV, "incompatible communication protocols\n");
+		goto disconnect;
+	}
+
+	if (cmp_after_sb(p_after_sb_0p, mdev->net_conf->after_sb_0p)) {
+		dev_err(DEV, "incompatible after-sb-0pri settings\n");
+		goto disconnect;
+	}
+
+	if (cmp_after_sb(p_after_sb_1p, mdev->net_conf->after_sb_1p)) {
+		dev_err(DEV, "incompatible after-sb-1pri settings\n");
+		goto disconnect;
+	}
+
+	if (cmp_after_sb(p_after_sb_2p, mdev->net_conf->after_sb_2p)) {
+		dev_err(DEV, "incompatible after-sb-2pri settings\n");
+		goto disconnect;
+	}
+
+	if (p_want_lose && mdev->net_conf->want_lose) {
+		dev_err(DEV, "both sides have the 'want_lose' flag set\n");
+		goto disconnect;
+	}
+
+	if (p_two_primaries != mdev->net_conf->two_primaries) {
+		dev_err(DEV, "incompatible setting of the two-primaries options\n");
+		goto disconnect;
+	}
+
+	if (mdev->agreed_pro_version >= 87) {
+		unsigned char *my_alg = mdev->net_conf->integrity_alg;
+
+		if (drbd_recv(mdev, p_integrity_alg, data_size) != data_size)
+			return FALSE;
+
+		p_integrity_alg[SHARED_SECRET_MAX-1] = 0;
+		if (strcmp(p_integrity_alg, my_alg)) {
+			dev_err(DEV, "incompatible setting of the data-integrity-alg\n");
+			goto disconnect;
+		}
+		dev_info(DEV, "data-integrity-alg: %s\n",
+		     my_alg[0] ? my_alg : (unsigned char *)"<not-used>");
+	}
+
+	return TRUE;
+
+disconnect:
+	drbd_force_state(mdev, NS(conn, C_DISCONNECTING));
+	return FALSE;
+}
+
+/* helper function
+ * input: alg name, feature name
+ * return: NULL (alg name was "")
+ *         ERR_PTR(error) if something goes wrong
+ *         or the crypto hash ptr, if it worked out ok. */
+struct crypto_hash *drbd_crypto_alloc_digest_safe(const struct drbd_conf *mdev,
+		const char *alg, const char *name)
+{
+	struct crypto_hash *tfm;
+
+	if (!alg[0])
+		return NULL;
+
+	tfm = crypto_alloc_hash(alg, 0, CRYPTO_ALG_ASYNC);
+	if (IS_ERR(tfm)) {
+		dev_err(DEV, "Can not allocate \"%s\" as %s (reason: %ld)\n",
+			alg, name, PTR_ERR(tfm));
+		return tfm;
+	}
+	if (!drbd_crypto_is_hash(crypto_hash_tfm(tfm))) {
+		crypto_free_hash(tfm);
+		dev_err(DEV, "\"%s\" is not a digest (%s)\n", alg, name);
+		return ERR_PTR(-EINVAL);
+	}
+	return tfm;
+}
+
+static int receive_SyncParam(struct drbd_conf *mdev, struct p_header *h)
+{
+	int ok = TRUE;
+	struct p_rs_param_89 *p = (struct p_rs_param_89 *)h;
+	unsigned int header_size, data_size, exp_max_sz;
+	struct crypto_hash *verify_tfm = NULL;
+	struct crypto_hash *csums_tfm = NULL;
+	const int apv = mdev->agreed_pro_version;
+
+	exp_max_sz  = apv <= 87 ? sizeof(struct p_rs_param)
+		    : apv == 88 ? sizeof(struct p_rs_param)
+					+ SHARED_SECRET_MAX
+		    : /* 89 */    sizeof(struct p_rs_param_89);
+
+	if (h->length > exp_max_sz) {
+		dev_err(DEV, "SyncParam packet too long: received %u, expected <= %u bytes\n",
+		    h->length, exp_max_sz);
+		return FALSE;
+	}
+
+	if (apv <= 88) {
+		header_size = sizeof(struct p_rs_param) - sizeof(*h);
+		data_size   = h->length  - header_size;
+	} else /* apv >= 89 */ {
+		header_size = sizeof(struct p_rs_param_89) - sizeof(*h);
+		data_size   = h->length  - header_size;
+		D_ASSERT(data_size == 0);
+	}
+
+	/* initialize verify_alg and csums_alg */
+	memset(p->verify_alg, 0, 2 * SHARED_SECRET_MAX);
+
+	if (drbd_recv(mdev, h->payload, header_size) != header_size)
+		return FALSE;
+
+	mdev->sync_conf.rate	  = be32_to_cpu(p->rate);
+
+	if (apv >= 88) {
+		if (apv == 88) {
+			if (data_size > SHARED_SECRET_MAX) {
+				dev_err(DEV, "verify-alg too long, "
+				    "peer wants %u, accepting only %u byte\n",
+						data_size, SHARED_SECRET_MAX);
+				return FALSE;
+			}
+
+			if (drbd_recv(mdev, p->verify_alg, data_size) != data_size)
+				return FALSE;
+
+			/* we expect NUL terminated string */
+			/* but just in case someone tries to be evil */
+			D_ASSERT(p->verify_alg[data_size-1] == 0);
+			p->verify_alg[data_size-1] = 0;
+
+		} else /* apv >= 89 */ {
+			/* we still expect NUL terminated strings */
+			/* but just in case someone tries to be evil */
+			D_ASSERT(p->verify_alg[SHARED_SECRET_MAX-1] == 0);
+			D_ASSERT(p->csums_alg[SHARED_SECRET_MAX-1] == 0);
+			p->verify_alg[SHARED_SECRET_MAX-1] = 0;
+			p->csums_alg[SHARED_SECRET_MAX-1] = 0;
+		}
+
+		if (strcmp(mdev->sync_conf.verify_alg, p->verify_alg)) {
+			if (mdev->state.conn == C_WF_REPORT_PARAMS) {
+				dev_err(DEV, "Different verify-alg settings. me=\"%s\" peer=\"%s\"\n",
+				    mdev->sync_conf.verify_alg, p->verify_alg);
+				goto disconnect;
+			}
+			verify_tfm = drbd_crypto_alloc_digest_safe(mdev,
+					p->verify_alg, "verify-alg");
+			if (IS_ERR(verify_tfm)) {
+				verify_tfm = NULL;
+				goto disconnect;
+			}
+		}
+
+		if (apv >= 89 && strcmp(mdev->sync_conf.csums_alg, p->csums_alg)) {
+			if (mdev->state.conn == C_WF_REPORT_PARAMS) {
+				dev_err(DEV, "Different csums-alg settings. me=\"%s\" peer=\"%s\"\n",
+				    mdev->sync_conf.csums_alg, p->csums_alg);
+				goto disconnect;
+			}
+			csums_tfm = drbd_crypto_alloc_digest_safe(mdev,
+					p->csums_alg, "csums-alg");
+			if (IS_ERR(csums_tfm)) {
+				csums_tfm = NULL;
+				goto disconnect;
+			}
+		}
+
+
+		spin_lock(&mdev->peer_seq_lock);
+		/* lock against drbd_nl_syncer_conf() */
+		if (verify_tfm) {
+			strcpy(mdev->sync_conf.verify_alg, p->verify_alg);
+			mdev->sync_conf.verify_alg_len = strlen(p->verify_alg) + 1;
+			crypto_free_hash(mdev->verify_tfm);
+			mdev->verify_tfm = verify_tfm;
+			dev_info(DEV, "using verify-alg: \"%s\"\n", p->verify_alg);
+		}
+		if (csums_tfm) {
+			strcpy(mdev->sync_conf.csums_alg, p->csums_alg);
+			mdev->sync_conf.csums_alg_len = strlen(p->csums_alg) + 1;
+			crypto_free_hash(mdev->csums_tfm);
+			mdev->csums_tfm = csums_tfm;
+			dev_info(DEV, "using csums-alg: \"%s\"\n", p->csums_alg);
+		}
+		spin_unlock(&mdev->peer_seq_lock);
+	}
+
+	return ok;
+disconnect:
+	/* just for completeness: actually not needed,
+	 * as this is not reached if csums_tfm was ok. */
+	crypto_free_hash(csums_tfm);
+	/* but free the verify_tfm again, if csums_tfm did not work out */
+	crypto_free_hash(verify_tfm);
+	drbd_force_state(mdev, NS(conn, C_DISCONNECTING));
+	return FALSE;
+}
+
+static void drbd_setup_order_type(struct drbd_conf *mdev, int peer)
+{
+	/* sorry, we currently have no working implementation
+	 * of distributed TCQ */
+}
+
+/* warn if the arguments differ by more than 12.5% */
+static void warn_if_differ_considerably(struct drbd_conf *mdev,
+	const char *s, sector_t a, sector_t b)
+{
+	sector_t d;
+	if (a == 0 || b == 0)
+		return;
+	d = (a > b) ? (a - b) : (b - a);
+	if (d > (a>>3) || d > (b>>3))
+		dev_warn(DEV, "Considerable difference in %s: %llus vs. %llus\n", s,
+		     (unsigned long long)a, (unsigned long long)b);
+}
+
+static int receive_sizes(struct drbd_conf *mdev, struct p_header *h)
+{
+	struct p_sizes *p = (struct p_sizes *)h;
+	enum determine_dev_size dd = unchanged;
+	unsigned int max_seg_s;
+	sector_t p_size, p_usize, my_usize;
+	int ldsc = 0; /* local disk size changed */
+	enum drbd_conns nconn;
+
+	ERR_IF(h->length != (sizeof(*p)-sizeof(*h))) return FALSE;
+	if (drbd_recv(mdev, h->payload, h->length) != h->length)
+		return FALSE;
+
+	p_size = be64_to_cpu(p->d_size);
+	p_usize = be64_to_cpu(p->u_size);
+
+	if (p_size == 0 && mdev->state.disk == D_DISKLESS) {
+		dev_err(DEV, "some backing storage is needed\n");
+		drbd_force_state(mdev, NS(conn, C_DISCONNECTING));
+		return FALSE;
+	}
+
+	/* just store the peer's disk size for now.
+	 * we still need to figure out whether we accept that. */
+	mdev->p_size = p_size;
+
+#define min_not_zero(l, r) (l == 0) ? r : ((r == 0) ? l : min(l, r))
+	if (get_ldev(mdev)) {
+		warn_if_differ_considerably(mdev, "lower level device sizes",
+			   p_size, drbd_get_max_capacity(mdev->ldev));
+		warn_if_differ_considerably(mdev, "user requested size",
+					    p_usize, mdev->ldev->dc.disk_size);
+
+		/* if this is the first connect, or an otherwise expected
+		 * param exchange, choose the minimum */
+		if (mdev->state.conn == C_WF_REPORT_PARAMS)
+			p_usize = min_not_zero((sector_t)mdev->ldev->dc.disk_size,
+					     p_usize);
+
+		my_usize = mdev->ldev->dc.disk_size;
+
+		if (mdev->ldev->dc.disk_size != p_usize) {
+			mdev->ldev->dc.disk_size = p_usize;
+			dev_info(DEV, "Peer sets u_size to %lu sectors\n",
+			     (unsigned long)mdev->ldev->dc.disk_size);
+		}
+
+		/* Never shrink a device with usable data during connect.
+		   But allow online shrinking if we are connected. */
+		if (drbd_new_dev_size(mdev, mdev->ldev) <
+		   drbd_get_capacity(mdev->this_bdev) &&
+		   mdev->state.disk >= D_OUTDATED &&
+		   mdev->state.conn < C_CONNECTED) {
+			dev_err(DEV, "The peer's disk size is too small!\n");
+			drbd_force_state(mdev, NS(conn, C_DISCONNECTING));
+			mdev->ldev->dc.disk_size = my_usize;
+			put_ldev(mdev);
+			return FALSE;
+		}
+		put_ldev(mdev);
+	}
+#undef min_not_zero
+
+	if (get_ldev(mdev)) {
+		dd = drbd_determin_dev_size(mdev);
+		put_ldev(mdev);
+		if (dd == dev_size_error)
+			return FALSE;
+		drbd_md_sync(mdev);
+	} else {
+		/* I am diskless, need to accept the peer's size. */
+		drbd_set_my_capacity(mdev, p_size);
+	}
+
+	if (mdev->p_uuid && mdev->state.conn <= C_CONNECTED && get_ldev(mdev)) {
+		nconn = drbd_sync_handshake(mdev,
+				mdev->state.peer, mdev->state.pdsk);
+		put_ldev(mdev);
+
+		if (nconn == C_MASK) {
+			drbd_force_state(mdev, NS(conn, C_DISCONNECTING));
+			return FALSE;
+		}
+
+		if (drbd_request_state(mdev, NS(conn, nconn)) < SS_SUCCESS) {
+			drbd_force_state(mdev, NS(conn, C_DISCONNECTING));
+			return FALSE;
+		}
+	}
+
+	if (get_ldev(mdev)) {
+		if (mdev->ldev->known_size != drbd_get_capacity(mdev->ldev->backing_bdev)) {
+			mdev->ldev->known_size = drbd_get_capacity(mdev->ldev->backing_bdev);
+			ldsc = 1;
+		}
+
+		max_seg_s = be32_to_cpu(p->max_segment_size);
+		if (max_seg_s != queue_max_segment_size(mdev->rq_queue))
+			drbd_setup_queue_param(mdev, max_seg_s);
+
+		drbd_setup_order_type(mdev, be32_to_cpu(p->queue_order_type));
+		put_ldev(mdev);
+	}
+
+	if (mdev->state.conn > C_WF_REPORT_PARAMS) {
+		if (be64_to_cpu(p->c_size) !=
+		    drbd_get_capacity(mdev->this_bdev) || ldsc) {
+			/* we have different sizes, probably peer
+			 * needs to know my new size... */
+			drbd_send_sizes(mdev, 0);
+		}
+		if (test_and_clear_bit(RESIZE_PENDING, &mdev->flags) ||
+		    (dd == grew && mdev->state.conn == C_CONNECTED)) {
+			if (mdev->state.pdsk >= D_INCONSISTENT &&
+			    mdev->state.disk >= D_INCONSISTENT)
+				resync_after_online_grow(mdev);
+			else
+				set_bit(RESYNC_AFTER_NEG, &mdev->flags);
+		}
+	}
+
+	return TRUE;
+}
+
+static int receive_uuids(struct drbd_conf *mdev, struct p_header *h)
+{
+	struct p_uuids *p = (struct p_uuids *)h;
+	u64 *p_uuid;
+	int i;
+
+	ERR_IF(h->length != (sizeof(*p)-sizeof(*h))) return FALSE;
+	if (drbd_recv(mdev, h->payload, h->length) != h->length)
+		return FALSE;
+
+	p_uuid = kmalloc(sizeof(u64)*UI_EXTENDED_SIZE, GFP_NOIO);
+
+	for (i = UI_CURRENT; i < UI_EXTENDED_SIZE; i++)
+		p_uuid[i] = be64_to_cpu(p->uuid[i]);
+
+	kfree(mdev->p_uuid);
+	mdev->p_uuid = p_uuid;
+
+	if (mdev->state.conn < C_CONNECTED &&
+	    mdev->state.disk < D_INCONSISTENT &&
+	    mdev->state.role == R_PRIMARY &&
+	    (mdev->ed_uuid & ~((u64)1)) != (p_uuid[UI_CURRENT] & ~((u64)1))) {
+		dev_err(DEV, "Can only connect to data with current UUID=%016llX\n",
+		    (unsigned long long)mdev->ed_uuid);
+		drbd_force_state(mdev, NS(conn, C_DISCONNECTING));
+		return FALSE;
+	}
+
+	if (get_ldev(mdev)) {
+		int skip_initial_sync =
+			mdev->state.conn == C_CONNECTED &&
+			mdev->agreed_pro_version >= 90 &&
+			mdev->ldev->md.uuid[UI_CURRENT] == UUID_JUST_CREATED &&
+			(p_uuid[UI_FLAGS] & 8);
+		if (skip_initial_sync) {
+			dev_info(DEV, "Accepted new current UUID, preparing to skip initial sync\n");
+			drbd_bitmap_io(mdev, &drbd_bmio_clear_n_write,
+					"clear_n_write from receive_uuids");
+			_drbd_uuid_set(mdev, UI_CURRENT, p_uuid[UI_CURRENT]);
+			_drbd_uuid_set(mdev, UI_BITMAP, 0);
+			_drbd_set_state(_NS2(mdev, disk, D_UP_TO_DATE, pdsk, D_UP_TO_DATE),
+					CS_VERBOSE, NULL);
+			drbd_md_sync(mdev);
+		}
+		put_ldev(mdev);
+	}
+
+	/* Before we test for the disk state, we should wait until an eventually
+	   ongoing cluster wide state change is finished. That is important if
+	   we are primary and are detaching from our disk. We need to see the
+	   new disk state... */
+	wait_event(mdev->misc_wait, !test_bit(CLUSTER_ST_CHANGE, &mdev->flags));
+	if (mdev->state.conn >= C_CONNECTED && mdev->state.disk < D_INCONSISTENT)
+		drbd_set_ed_uuid(mdev, p_uuid[UI_CURRENT]);
+
+	return TRUE;
+}
+
+/**
+ * convert_state() - Converts the peer's view of the cluster state to our point of view
+ * @ps:		The state as seen by the peer.
+ */
+static union drbd_state convert_state(union drbd_state ps)
+{
+	union drbd_state ms;
+
+	static enum drbd_conns c_tab[] = {
+		[C_CONNECTED] = C_CONNECTED,
+
+		[C_STARTING_SYNC_S] = C_STARTING_SYNC_T,
+		[C_STARTING_SYNC_T] = C_STARTING_SYNC_S,
+		[C_DISCONNECTING] = C_TEAR_DOWN, /* C_NETWORK_FAILURE, */
+		[C_VERIFY_S]       = C_VERIFY_T,
+		[C_MASK]   = C_MASK,
+	};
+
+	ms.i = ps.i;
+
+	ms.conn = c_tab[ps.conn];
+	ms.peer = ps.role;
+	ms.role = ps.peer;
+	ms.pdsk = ps.disk;
+	ms.disk = ps.pdsk;
+	ms.peer_isp = (ps.aftr_isp | ps.user_isp);
+
+	return ms;
+}
+
+static int receive_req_state(struct drbd_conf *mdev, struct p_header *h)
+{
+	struct p_req_state *p = (struct p_req_state *)h;
+	union drbd_state mask, val;
+	int rv;
+
+	ERR_IF(h->length != (sizeof(*p)-sizeof(*h))) return FALSE;
+	if (drbd_recv(mdev, h->payload, h->length) != h->length)
+		return FALSE;
+
+	mask.i = be32_to_cpu(p->mask);
+	val.i = be32_to_cpu(p->val);
+
+	if (test_bit(DISCARD_CONCURRENT, &mdev->flags) &&
+	    test_bit(CLUSTER_ST_CHANGE, &mdev->flags)) {
+		drbd_send_sr_reply(mdev, SS_CONCURRENT_ST_CHG);
+		return TRUE;
+	}
+
+	mask = convert_state(mask);
+	val = convert_state(val);
+
+	rv = drbd_change_state(mdev, CS_VERBOSE, mask, val);
+
+	drbd_send_sr_reply(mdev, rv);
+	drbd_md_sync(mdev);
+
+	return TRUE;
+}
+
+static int receive_state(struct drbd_conf *mdev, struct p_header *h)
+{
+	struct p_state *p = (struct p_state *)h;
+	enum drbd_conns nconn, oconn;
+	union drbd_state ns, peer_state;
+	enum drbd_disk_state real_peer_disk;
+	int rv;
+
+	ERR_IF(h->length != (sizeof(*p)-sizeof(*h)))
+		return FALSE;
+
+	if (drbd_recv(mdev, h->payload, h->length) != h->length)
+		return FALSE;
+
+	peer_state.i = be32_to_cpu(p->state);
+
+	real_peer_disk = peer_state.disk;
+	if (peer_state.disk == D_NEGOTIATING) {
+		real_peer_disk = mdev->p_uuid[UI_FLAGS] & 4 ? D_INCONSISTENT : D_CONSISTENT;
+		dev_info(DEV, "real peer disk state = %s\n", drbd_disk_str(real_peer_disk));
+	}
+
+	spin_lock_irq(&mdev->req_lock);
+ retry:
+	oconn = nconn = mdev->state.conn;
+	spin_unlock_irq(&mdev->req_lock);
+
+	if (nconn == C_WF_REPORT_PARAMS)
+		nconn = C_CONNECTED;
+
+	if (mdev->p_uuid && peer_state.disk >= D_NEGOTIATING &&
+	    get_ldev_if_state(mdev, D_NEGOTIATING)) {
+		int cr; /* consider resync */
+
+		/* if we established a new connection */
+		cr  = (oconn < C_CONNECTED);
+		/* if we had an established connection
+		 * and one of the nodes newly attaches a disk */
+		cr |= (oconn == C_CONNECTED &&
+		       (peer_state.disk == D_NEGOTIATING ||
+			mdev->state.disk == D_NEGOTIATING));
+		/* if we have both been inconsistent, and the peer has been
+		 * forced to be UpToDate with --overwrite-data */
+		cr |= test_bit(CONSIDER_RESYNC, &mdev->flags);
+		/* if we had been plain connected, and the admin requested to
+		 * start a sync by "invalidate" or "invalidate-remote" */
+		cr |= (oconn == C_CONNECTED &&
+				(peer_state.conn >= C_STARTING_SYNC_S &&
+				 peer_state.conn <= C_WF_BITMAP_T));
+
+		if (cr)
+			nconn = drbd_sync_handshake(mdev, peer_state.role, real_peer_disk);
+
+		put_ldev(mdev);
+		if (nconn == C_MASK) {
+			if (mdev->state.disk == D_NEGOTIATING) {
+				drbd_force_state(mdev, NS(disk, D_DISKLESS));
+				nconn = C_CONNECTED;
+			} else if (peer_state.disk == D_NEGOTIATING) {
+				dev_err(DEV, "Disk attach process on the peer node was aborted.\n");
+				peer_state.disk = D_DISKLESS;
+			} else {
+				D_ASSERT(oconn == C_WF_REPORT_PARAMS);
+				drbd_force_state(mdev, NS(conn, C_DISCONNECTING));
+				return FALSE;
+			}
+		}
+	}
+
+	spin_lock_irq(&mdev->req_lock);
+	if (mdev->state.conn != oconn)
+		goto retry;
+	clear_bit(CONSIDER_RESYNC, &mdev->flags);
+	ns.i = mdev->state.i;
+	ns.conn = nconn;
+	ns.peer = peer_state.role;
+	ns.pdsk = real_peer_disk;
+	ns.peer_isp = (peer_state.aftr_isp | peer_state.user_isp);
+	if ((nconn == C_CONNECTED || nconn == C_WF_BITMAP_S) && ns.disk == D_NEGOTIATING)
+		ns.disk = mdev->new_state_tmp.disk;
+
+	rv = _drbd_set_state(mdev, ns, CS_VERBOSE | CS_HARD, NULL);
+	ns = mdev->state;
+	spin_unlock_irq(&mdev->req_lock);
+
+	if (rv < SS_SUCCESS) {
+		drbd_force_state(mdev, NS(conn, C_DISCONNECTING));
+		return FALSE;
+	}
+
+	if (oconn > C_WF_REPORT_PARAMS) {
+		if (nconn > C_CONNECTED && peer_state.conn <= C_CONNECTED &&
+		    peer_state.disk != D_NEGOTIATING ) {
+			/* we want resync, peer has not yet decided to sync... */
+			/* Nowadays only used when forcing a node into primary role and
+			   setting its disk to UpToDate with that */
+			drbd_send_uuids(mdev);
+			drbd_send_state(mdev);
+		}
+	}
+
+	mdev->net_conf->want_lose = 0;
+
+	drbd_md_sync(mdev); /* update connected indicator, la_size, ... */
+
+	return TRUE;
+}
+
+static int receive_sync_uuid(struct drbd_conf *mdev, struct p_header *h)
+{
+	struct p_rs_uuid *p = (struct p_rs_uuid *)h;
+
+	wait_event(mdev->misc_wait,
+		   mdev->state.conn == C_WF_SYNC_UUID ||
+		   mdev->state.conn < C_CONNECTED ||
+		   mdev->state.disk < D_NEGOTIATING);
+
+	/* D_ASSERT( mdev->state.conn == C_WF_SYNC_UUID ); */
+
+	ERR_IF(h->length != (sizeof(*p)-sizeof(*h))) return FALSE;
+	if (drbd_recv(mdev, h->payload, h->length) != h->length)
+		return FALSE;
+
+	/* Here the _drbd_uuid_ functions are right, current should
+	   _not_ be rotated into the history */
+	if (get_ldev_if_state(mdev, D_NEGOTIATING)) {
+		_drbd_uuid_set(mdev, UI_CURRENT, be64_to_cpu(p->uuid));
+		_drbd_uuid_set(mdev, UI_BITMAP, 0UL);
+
+		drbd_start_resync(mdev, C_SYNC_TARGET);
+
+		put_ldev(mdev);
+	} else
+		dev_err(DEV, "Ignoring SyncUUID packet!\n");
+
+	return TRUE;
+}
+
+enum receive_bitmap_ret { OK, DONE, FAILED };
+
+static enum receive_bitmap_ret
+receive_bitmap_plain(struct drbd_conf *mdev, struct p_header *h,
+	unsigned long *buffer, struct bm_xfer_ctx *c)
+{
+	unsigned num_words = min_t(size_t, BM_PACKET_WORDS, c->bm_words - c->word_offset);
+	unsigned want = num_words * sizeof(long);
+
+	if (want != h->length) {
+		dev_err(DEV, "%s:want (%u) != h->length (%u)\n", __func__, want, h->length);
+		return FAILED;
+	}
+	if (want == 0)
+		return DONE;
+	if (drbd_recv(mdev, buffer, want) != want)
+		return FAILED;
+
+	drbd_bm_merge_lel(mdev, c->word_offset, num_words, buffer);
+
+	c->word_offset += num_words;
+	c->bit_offset = c->word_offset * BITS_PER_LONG;
+	if (c->bit_offset > c->bm_bits)
+		c->bit_offset = c->bm_bits;
+
+	return OK;
+}
+
+static enum receive_bitmap_ret
+recv_bm_rle_bits(struct drbd_conf *mdev,
+		struct p_compressed_bm *p,
+		struct bm_xfer_ctx *c)
+{
+	struct bitstream bs;
+	u64 look_ahead;
+	u64 rl;
+	u64 tmp;
+	unsigned long s = c->bit_offset;
+	unsigned long e;
+	int len = p->head.length - (sizeof(*p) - sizeof(p->head));
+	int toggle = DCBP_get_start(p);
+	int have;
+	int bits;
+
+	bitstream_init(&bs, p->code, len, DCBP_get_pad_bits(p));
+
+	bits = bitstream_get_bits(&bs, &look_ahead, 64);
+	if (bits < 0)
+		return FAILED;
+
+	for (have = bits; have > 0; s += rl, toggle = !toggle) {
+		bits = vli_decode_bits(&rl, look_ahead);
+		if (bits <= 0)
+			return FAILED;
+
+		if (toggle) {
+			e = s + rl -1;
+			if (e >= c->bm_bits) {
+				dev_err(DEV, "bitmap overflow (e:%lu) while decoding bm RLE packet\n", e);
+				return FAILED;
+			}
+			_drbd_bm_set_bits(mdev, s, e);
+		}
+
+		if (have < bits) {
+			dev_err(DEV, "bitmap decoding error: h:%d b:%d la:0x%08llx l:%u/%u\n",
+				have, bits, look_ahead,
+				(unsigned int)(bs.cur.b - p->code),
+				(unsigned int)bs.buf_len);
+			return FAILED;
+		}
+		look_ahead >>= bits;
+		have -= bits;
+
+		bits = bitstream_get_bits(&bs, &tmp, 64 - have);
+		if (bits < 0)
+			return FAILED;
+		look_ahead |= tmp << have;
+		have += bits;
+	}
+
+	c->bit_offset = s;
+	bm_xfer_ctx_bit_to_word_offset(c);
+
+	return (s == c->bm_bits) ? DONE : OK;
+}
+
+static enum receive_bitmap_ret
+decode_bitmap_c(struct drbd_conf *mdev,
+		struct p_compressed_bm *p,
+		struct bm_xfer_ctx *c)
+{
+	if (DCBP_get_code(p) == RLE_VLI_Bits)
+		return recv_bm_rle_bits(mdev, p, c);
+
+	/* other variants had been implemented for evaluation,
+	 * but have been dropped as this one turned out to be "best"
+	 * during all our tests. */
+
+	dev_err(DEV, "receive_bitmap_c: unknown encoding %u\n", p->encoding);
+	drbd_force_state(mdev, NS(conn, C_PROTOCOL_ERROR));
+	return FAILED;
+}
+
+void INFO_bm_xfer_stats(struct drbd_conf *mdev,
+		const char *direction, struct bm_xfer_ctx *c)
+{
+	/* what would it take to transfer it "plaintext" */
+	unsigned plain = sizeof(struct p_header) *
+		((c->bm_words+BM_PACKET_WORDS-1)/BM_PACKET_WORDS+1)
+		+ c->bm_words * sizeof(long);
+	unsigned total = c->bytes[0] + c->bytes[1];
+	unsigned r;
+
+	/* total can not be zero. but just in case: */
+	if (total == 0)
+		return;
+
+	/* don't report if not compressed */
+	if (total >= plain)
+		return;
+
+	/* total < plain. check for overflow, still */
+	r = (total > UINT_MAX/1000) ? (total / (plain/1000))
+		                    : (1000 * total / plain);
+
+	if (r > 1000)
+		r = 1000;
+
+	r = 1000 - r;
+	dev_info(DEV, "%s bitmap stats [Bytes(packets)]: plain %u(%u), RLE %u(%u), "
+	     "total %u; compression: %u.%u%%\n",
+			direction,
+			c->bytes[1], c->packets[1],
+			c->bytes[0], c->packets[0],
+			total, r/10, r % 10);
+}
+
+/* Since we are processing the bitfield from lower addresses to higher,
+   it does not matter if the process it in 32 bit chunks or 64 bit
+   chunks as long as it is little endian. (Understand it as byte stream,
+   beginning with the lowest byte...) If we would use big endian
+   we would need to process it from the highest address to the lowest,
+   in order to be agnostic to the 32 vs 64 bits issue.
+
+   returns 0 on failure, 1 if we successfully received it. */
+static int receive_bitmap(struct drbd_conf *mdev, struct p_header *h)
+{
+	struct bm_xfer_ctx c;
+	void *buffer;
+	enum receive_bitmap_ret ret;
+	int ok = FALSE;
+
+	wait_event(mdev->misc_wait, !atomic_read(&mdev->ap_bio_cnt));
+
+	drbd_bm_lock(mdev, "receive bitmap");
+
+	/* maybe we should use some per thread scratch page,
+	 * and allocate that during initial device creation? */
+	buffer	 = (unsigned long *) __get_free_page(GFP_NOIO);
+	if (!buffer) {
+		dev_err(DEV, "failed to allocate one page buffer in %s\n", __func__);
+		goto out;
+	}
+
+	c = (struct bm_xfer_ctx) {
+		.bm_bits = drbd_bm_bits(mdev),
+		.bm_words = drbd_bm_words(mdev),
+	};
+
+	do {
+		if (h->command == P_BITMAP) {
+			ret = receive_bitmap_plain(mdev, h, buffer, &c);
+		} else if (h->command == P_COMPRESSED_BITMAP) {
+			/* MAYBE: sanity check that we speak proto >= 90,
+			 * and the feature is enabled! */
+			struct p_compressed_bm *p;
+
+			if (h->length > BM_PACKET_PAYLOAD_BYTES) {
+				dev_err(DEV, "ReportCBitmap packet too large\n");
+				goto out;
+			}
+			/* use the page buff */
+			p = buffer;
+			memcpy(p, h, sizeof(*h));
+			if (drbd_recv(mdev, p->head.payload, h->length) != h->length)
+				goto out;
+			if (p->head.length <= (sizeof(*p) - sizeof(p->head))) {
+				dev_err(DEV, "ReportCBitmap packet too small (l:%u)\n", p->head.length);
+				return FAILED;
+			}
+			ret = decode_bitmap_c(mdev, p, &c);
+		} else {
+			dev_warn(DEV, "receive_bitmap: h->command neither ReportBitMap nor ReportCBitMap (is 0x%x)", h->command);
+			goto out;
+		}
+
+		c.packets[h->command == P_BITMAP]++;
+		c.bytes[h->command == P_BITMAP] += sizeof(struct p_header) + h->length;
+
+		if (ret != OK)
+			break;
+
+		if (!drbd_recv_header(mdev, h))
+			goto out;
+	} while (ret == OK);
+	if (ret == FAILED)
+		goto out;
+
+	INFO_bm_xfer_stats(mdev, "receive", &c);
+
+	if (mdev->state.conn == C_WF_BITMAP_T) {
+		ok = !drbd_send_bitmap(mdev);
+		if (!ok)
+			goto out;
+		/* Omit CS_ORDERED with this state transition to avoid deadlocks. */
+		ok = _drbd_request_state(mdev, NS(conn, C_WF_SYNC_UUID), CS_VERBOSE);
+		D_ASSERT(ok == SS_SUCCESS);
+	} else if (mdev->state.conn != C_WF_BITMAP_S) {
+		/* admin may have requested C_DISCONNECTING,
+		 * other threads may have noticed network errors */
+		dev_info(DEV, "unexpected cstate (%s) in receive_bitmap\n",
+		    drbd_conn_str(mdev->state.conn));
+	}
+
+	ok = TRUE;
+ out:
+	drbd_bm_unlock(mdev);
+	if (ok && mdev->state.conn == C_WF_BITMAP_S)
+		drbd_start_resync(mdev, C_SYNC_SOURCE);
+	free_page((unsigned long) buffer);
+	return ok;
+}
+
+static int receive_skip(struct drbd_conf *mdev, struct p_header *h)
+{
+	/* TODO zero copy sink :) */
+	static char sink[128];
+	int size, want, r;
+
+	dev_warn(DEV, "skipping unknown optional packet type %d, l: %d!\n",
+	     h->command, h->length);
+
+	size = h->length;
+	while (size > 0) {
+		want = min_t(int, size, sizeof(sink));
+		r = drbd_recv(mdev, sink, want);
+		ERR_IF(r <= 0) break;
+		size -= r;
+	}
+	return size == 0;
+}
+
+static int receive_UnplugRemote(struct drbd_conf *mdev, struct p_header *h)
+{
+	if (mdev->state.disk >= D_INCONSISTENT)
+		drbd_kick_lo(mdev);
+
+	/* Make sure we've acked all the TCP data associated
+	 * with the data requests being unplugged */
+	drbd_tcp_quickack(mdev->data.socket);
+
+	return TRUE;
+}
+
+typedef int (*drbd_cmd_handler_f)(struct drbd_conf *, struct p_header *);
+
+static drbd_cmd_handler_f drbd_default_handler[] = {
+	[P_DATA]	    = receive_Data,
+	[P_DATA_REPLY]	    = receive_DataReply,
+	[P_RS_DATA_REPLY]   = receive_RSDataReply,
+	[P_BARRIER]	    = receive_Barrier,
+	[P_BITMAP]	    = receive_bitmap,
+	[P_COMPRESSED_BITMAP]    = receive_bitmap,
+	[P_UNPLUG_REMOTE]   = receive_UnplugRemote,
+	[P_DATA_REQUEST]    = receive_DataRequest,
+	[P_RS_DATA_REQUEST] = receive_DataRequest,
+	[P_SYNC_PARAM]	    = receive_SyncParam,
+	[P_SYNC_PARAM89]	   = receive_SyncParam,
+	[P_PROTOCOL]        = receive_protocol,
+	[P_UUIDS]	    = receive_uuids,
+	[P_SIZES]	    = receive_sizes,
+	[P_STATE]	    = receive_state,
+	[P_STATE_CHG_REQ]   = receive_req_state,
+	[P_SYNC_UUID]       = receive_sync_uuid,
+	[P_OV_REQUEST]      = receive_DataRequest,
+	[P_OV_REPLY]        = receive_DataRequest,
+	[P_CSUM_RS_REQUEST]    = receive_DataRequest,
+	/* anything missing from this table is in
+	 * the asender_tbl, see get_asender_cmd */
+	[P_MAX_CMD]	    = NULL,
+};
+
+static drbd_cmd_handler_f *drbd_cmd_handler = drbd_default_handler;
+static drbd_cmd_handler_f *drbd_opt_cmd_handler;
+
+static void drbdd(struct drbd_conf *mdev)
+{
+	drbd_cmd_handler_f handler;
+	struct p_header *header = &mdev->data.rbuf.header;
+
+	while (get_t_state(&mdev->receiver) == Running) {
+		drbd_thread_current_set_cpu(mdev);
+		if (!drbd_recv_header(mdev, header))
+			break;
+
+		if (header->command < P_MAX_CMD)
+			handler = drbd_cmd_handler[header->command];
+		else if (P_MAY_IGNORE < header->command
+		     && header->command < P_MAX_OPT_CMD)
+			handler = drbd_opt_cmd_handler[header->command-P_MAY_IGNORE];
+		else if (header->command > P_MAX_OPT_CMD)
+			handler = receive_skip;
+		else
+			handler = NULL;
+
+		if (unlikely(!handler)) {
+			dev_err(DEV, "unknown packet type %d, l: %d!\n",
+			    header->command, header->length);
+			drbd_force_state(mdev, NS(conn, C_PROTOCOL_ERROR));
+			break;
+		}
+		if (unlikely(!handler(mdev, header))) {
+			dev_err(DEV, "error receiving %s, l: %d!\n",
+			    cmdname(header->command), header->length);
+			drbd_force_state(mdev, NS(conn, C_PROTOCOL_ERROR));
+			break;
+		}
+
+		trace_drbd_packet(mdev, mdev->data.socket, 2, &mdev->data.rbuf,
+				__FILE__, __LINE__);
+	}
+}
+
+static void drbd_fail_pending_reads(struct drbd_conf *mdev)
+{
+	struct hlist_head *slot;
+	struct hlist_node *pos;
+	struct hlist_node *tmp;
+	struct drbd_request *req;
+	int i;
+
+	/*
+	 * Application READ requests
+	 */
+	spin_lock_irq(&mdev->req_lock);
+	for (i = 0; i < APP_R_HSIZE; i++) {
+		slot = mdev->app_reads_hash+i;
+		hlist_for_each_entry_safe(req, pos, tmp, slot, colision) {
+			/* it may (but should not any longer!)
+			 * be on the work queue; if that assert triggers,
+			 * we need to also grab the
+			 * spin_lock_irq(&mdev->data.work.q_lock);
+			 * and list_del_init here. */
+			D_ASSERT(list_empty(&req->w.list));
+			/* It would be nice to complete outside of spinlock.
+			 * But this is easier for now. */
+			_req_mod(req, connection_lost_while_pending);
+		}
+	}
+	for (i = 0; i < APP_R_HSIZE; i++)
+		if (!hlist_empty(mdev->app_reads_hash+i))
+			dev_warn(DEV, "ASSERT FAILED: app_reads_hash[%d].first: "
+				"%p, should be NULL\n", i, mdev->app_reads_hash[i].first);
+
+	memset(mdev->app_reads_hash, 0, APP_R_HSIZE*sizeof(void *));
+	spin_unlock_irq(&mdev->req_lock);
+}
+
+void drbd_flush_workqueue(struct drbd_conf *mdev)
+{
+	struct drbd_wq_barrier barr;
+
+	barr.w.cb = w_prev_work_done;
+	init_completion(&barr.done);
+	drbd_queue_work(&mdev->data.work, &barr.w);
+	wait_for_completion(&barr.done);
+}
+
+static void drbd_disconnect(struct drbd_conf *mdev)
+{
+	enum drbd_fencing_p fp;
+	union drbd_state os, ns;
+	int rv = SS_UNKNOWN_ERROR;
+	unsigned int i;
+
+	if (mdev->state.conn == C_STANDALONE)
+		return;
+	if (mdev->state.conn >= C_WF_CONNECTION)
+		dev_err(DEV, "ASSERT FAILED cstate = %s, expected < WFConnection\n",
+				drbd_conn_str(mdev->state.conn));
+
+	/* asender does not clean up anything. it must not interfere, either */
+	drbd_thread_stop(&mdev->asender);
+
+	mutex_lock(&mdev->data.mutex);
+	drbd_free_sock(mdev);
+	mutex_unlock(&mdev->data.mutex);
+
+	spin_lock_irq(&mdev->req_lock);
+	_drbd_wait_ee_list_empty(mdev, &mdev->active_ee);
+	_drbd_wait_ee_list_empty(mdev, &mdev->sync_ee);
+	_drbd_wait_ee_list_empty(mdev, &mdev->read_ee);
+	spin_unlock_irq(&mdev->req_lock);
+
+	/* We do not have data structures that would allow us to
+	 * get the rs_pending_cnt down to 0 again.
+	 *  * On C_SYNC_TARGET we do not have any data structures describing
+	 *    the pending RSDataRequest's we have sent.
+	 *  * On C_SYNC_SOURCE there is no data structure that tracks
+	 *    the P_RS_DATA_REPLY blocks that we sent to the SyncTarget.
+	 *  And no, it is not the sum of the reference counts in the
+	 *  resync_LRU. The resync_LRU tracks the whole operation including
+	 *  the disk-IO, while the rs_pending_cnt only tracks the blocks
+	 *  on the fly. */
+	drbd_rs_cancel_all(mdev);
+	mdev->rs_total = 0;
+	mdev->rs_failed = 0;
+	atomic_set(&mdev->rs_pending_cnt, 0);
+	wake_up(&mdev->misc_wait);
+
+	/* make sure syncer is stopped and w_resume_next_sg queued */
+	del_timer_sync(&mdev->resync_timer);
+	set_bit(STOP_SYNC_TIMER, &mdev->flags);
+	resync_timer_fn((unsigned long)mdev);
+
+	/* so we can be sure that all remote or resync reads
+	 * made it at least to net_ee */
+	wait_event(mdev->misc_wait, !atomic_read(&mdev->local_cnt));
+
+	/* wait for all w_e_end_data_req, w_e_end_rsdata_req, w_send_barrier,
+	 * w_make_resync_request etc. which may still be on the worker queue
+	 * to be "canceled" */
+	drbd_flush_workqueue(mdev);
+
+	/* This also does reclaim_net_ee().  If we do this too early, we might
+	 * miss some resync ee and pages.*/
+	drbd_process_done_ee(mdev);
+
+	kfree(mdev->p_uuid);
+	mdev->p_uuid = NULL;
+
+	if (!mdev->state.susp)
+		tl_clear(mdev);
+
+	drbd_fail_pending_reads(mdev);
+
+	dev_info(DEV, "Connection closed\n");
+
+	drbd_md_sync(mdev);
+
+	fp = FP_DONT_CARE;
+	if (get_ldev(mdev)) {
+		fp = mdev->ldev->dc.fencing;
+		put_ldev(mdev);
+	}
+
+	if (mdev->state.role == R_PRIMARY) {
+		if (fp >= FP_RESOURCE && mdev->state.pdsk >= D_UNKNOWN) {
+			enum drbd_disk_state nps = drbd_try_outdate_peer(mdev);
+			drbd_request_state(mdev, NS(pdsk, nps));
+		}
+	}
+
+	spin_lock_irq(&mdev->req_lock);
+	os = mdev->state;
+	if (os.conn >= C_UNCONNECTED) {
+		/* Do not restart in case we are C_DISCONNECTING */
+		ns = os;
+		ns.conn = C_UNCONNECTED;
+		rv = _drbd_set_state(mdev, ns, CS_VERBOSE, NULL);
+	}
+	spin_unlock_irq(&mdev->req_lock);
+
+	if (os.conn == C_DISCONNECTING) {
+		struct hlist_head *h;
+		wait_event(mdev->misc_wait, atomic_read(&mdev->net_cnt) == 0);
+
+		/* we must not free the tl_hash
+		 * while application io is still on the fly */
+		wait_event(mdev->misc_wait, atomic_read(&mdev->ap_bio_cnt) == 0);
+
+		spin_lock_irq(&mdev->req_lock);
+		/* paranoia code */
+		for (h = mdev->ee_hash; h < mdev->ee_hash + mdev->ee_hash_s; h++)
+			if (h->first)
+				dev_err(DEV, "ASSERT FAILED ee_hash[%u].first == %p, expected NULL\n",
+						(int)(h - mdev->ee_hash), h->first);
+		kfree(mdev->ee_hash);
+		mdev->ee_hash = NULL;
+		mdev->ee_hash_s = 0;
+
+		/* paranoia code */
+		for (h = mdev->tl_hash; h < mdev->tl_hash + mdev->tl_hash_s; h++)
+			if (h->first)
+				dev_err(DEV, "ASSERT FAILED tl_hash[%u] == %p, expected NULL\n",
+						(int)(h - mdev->tl_hash), h->first);
+		kfree(mdev->tl_hash);
+		mdev->tl_hash = NULL;
+		mdev->tl_hash_s = 0;
+		spin_unlock_irq(&mdev->req_lock);
+
+		crypto_free_hash(mdev->cram_hmac_tfm);
+		mdev->cram_hmac_tfm = NULL;
+
+		kfree(mdev->net_conf);
+		mdev->net_conf = NULL;
+		drbd_request_state(mdev, NS(conn, C_STANDALONE));
+	}
+
+	/* tcp_close and release of sendpage pages can be deferred.  I don't
+	 * want to use SO_LINGER, because apparently it can be deferred for
+	 * more than 20 seconds (longest time I checked).
+	 *
+	 * Actually we don't care for exactly when the network stack does its
+	 * put_page(), but release our reference on these pages right here.
+	 */
+	i = drbd_release_ee(mdev, &mdev->net_ee);
+	if (i)
+		dev_info(DEV, "net_ee not empty, killed %u entries\n", i);
+	i = atomic_read(&mdev->pp_in_use);
+	if (i)
+		dev_info(DEV, "pp_in_use = %u, expected 0\n", i);
+
+	D_ASSERT(list_empty(&mdev->read_ee));
+	D_ASSERT(list_empty(&mdev->active_ee));
+	D_ASSERT(list_empty(&mdev->sync_ee));
+	D_ASSERT(list_empty(&mdev->done_ee));
+
+	/* ok, no more ee's on the fly, it is safe to reset the epoch_size */
+	atomic_set(&mdev->current_epoch->epoch_size, 0);
+	D_ASSERT(list_empty(&mdev->current_epoch->list));
+}
+
+/*
+ * We support PRO_VERSION_MIN to PRO_VERSION_MAX. The protocol version
+ * we can agree on is stored in agreed_pro_version.
+ *
+ * feature flags and the reserved array should be enough room for future
+ * enhancements of the handshake protocol, and possible plugins...
+ *
+ * for now, they are expected to be zero, but ignored.
+ */
+static int drbd_send_handshake(struct drbd_conf *mdev)
+{
+	/* ASSERT current == mdev->receiver ... */
+	struct p_handshake *p = &mdev->data.sbuf.handshake;
+	int ok;
+
+	if (mutex_lock_interruptible(&mdev->data.mutex)) {
+		dev_err(DEV, "interrupted during initial handshake\n");
+		return 0; /* interrupted. not ok. */
+	}
+
+	if (mdev->data.socket == NULL) {
+		mutex_unlock(&mdev->data.mutex);
+		return 0;
+	}
+
+	memset(p, 0, sizeof(*p));
+	p->protocol_min = cpu_to_be32(PRO_VERSION_MIN);
+	p->protocol_max = cpu_to_be32(PRO_VERSION_MAX);
+	ok = _drbd_send_cmd( mdev, mdev->data.socket, P_HAND_SHAKE,
+			     (struct p_header *)p, sizeof(*p), 0 );
+	mutex_unlock(&mdev->data.mutex);
+	return ok;
+}
+
+/*
+ * return values:
+ *   1 yes, we have a valid connection
+ *   0 oops, did not work out, please try again
+ *  -1 peer talks different language,
+ *     no point in trying again, please go standalone.
+ */
+static int drbd_do_handshake(struct drbd_conf *mdev)
+{
+	/* ASSERT current == mdev->receiver ... */
+	struct p_handshake *p = &mdev->data.rbuf.handshake;
+	const int expect = sizeof(struct p_handshake)
+			  -sizeof(struct p_header);
+	int rv;
+
+	rv = drbd_send_handshake(mdev);
+	if (!rv)
+		return 0;
+
+	rv = drbd_recv_header(mdev, &p->head);
+	if (!rv)
+		return 0;
+
+	if (p->head.command != P_HAND_SHAKE) {
+		dev_err(DEV, "expected HandShake packet, received: %s (0x%04x)\n",
+		     cmdname(p->head.command), p->head.command);
+		return -1;
+	}
+
+	if (p->head.length != expect) {
+		dev_err(DEV, "expected HandShake length: %u, received: %u\n",
+		     expect, p->head.length);
+		return -1;
+	}
+
+	rv = drbd_recv(mdev, &p->head.payload, expect);
+
+	if (rv != expect) {
+		dev_err(DEV, "short read receiving handshake packet: l=%u\n", rv);
+		return 0;
+	}
+
+	trace_drbd_packet(mdev, mdev->data.socket, 2, &mdev->data.rbuf,
+			__FILE__, __LINE__);
+
+	p->protocol_min = be32_to_cpu(p->protocol_min);
+	p->protocol_max = be32_to_cpu(p->protocol_max);
+	if (p->protocol_max == 0)
+		p->protocol_max = p->protocol_min;
+
+	if (PRO_VERSION_MAX < p->protocol_min ||
+	    PRO_VERSION_MIN > p->protocol_max)
+		goto incompat;
+
+	mdev->agreed_pro_version = min_t(int, PRO_VERSION_MAX, p->protocol_max);
+
+	dev_info(DEV, "Handshake successful: "
+	     "Agreed network protocol version %d\n", mdev->agreed_pro_version);
+
+	return 1;
+
+ incompat:
+	dev_err(DEV, "incompatible DRBD dialects: "
+	    "I support %d-%d, peer supports %d-%d\n",
+	    PRO_VERSION_MIN, PRO_VERSION_MAX,
+	    p->protocol_min, p->protocol_max);
+	return -1;
+}
+
+#if !defined(CONFIG_CRYPTO_HMAC) && !defined(CONFIG_CRYPTO_HMAC_MODULE)
+static int drbd_do_auth(struct drbd_conf *mdev)
+{
+	dev_err(DEV, "This kernel was build without CONFIG_CRYPTO_HMAC.\n");
+	dev_err(DEV, "You need to disable 'cram-hmac-alg' in drbd.conf.\n");
+	return 0;
+}
+#else
+#define CHALLENGE_LEN 64
+static int drbd_do_auth(struct drbd_conf *mdev)
+{
+	char my_challenge[CHALLENGE_LEN];  /* 64 Bytes... */
+	struct scatterlist sg;
+	char *response = NULL;
+	char *right_response = NULL;
+	char *peers_ch = NULL;
+	struct p_header p;
+	unsigned int key_len = strlen(mdev->net_conf->shared_secret);
+	unsigned int resp_size;
+	struct hash_desc desc;
+	int rv;
+
+	desc.tfm = mdev->cram_hmac_tfm;
+	desc.flags = 0;
+
+	rv = crypto_hash_setkey(mdev->cram_hmac_tfm,
+				(u8 *)mdev->net_conf->shared_secret, key_len);
+	if (rv) {
+		dev_err(DEV, "crypto_hash_setkey() failed with %d\n", rv);
+		rv = 0;
+		goto fail;
+	}
+
+	get_random_bytes(my_challenge, CHALLENGE_LEN);
+
+	rv = drbd_send_cmd2(mdev, P_AUTH_CHALLENGE, my_challenge, CHALLENGE_LEN);
+	if (!rv)
+		goto fail;
+
+	rv = drbd_recv_header(mdev, &p);
+	if (!rv)
+		goto fail;
+
+	if (p.command != P_AUTH_CHALLENGE) {
+		dev_err(DEV, "expected AuthChallenge packet, received: %s (0x%04x)\n",
+		    cmdname(p.command), p.command);
+		rv = 0;
+		goto fail;
+	}
+
+	if (p.length > CHALLENGE_LEN*2) {
+		dev_err(DEV, "expected AuthChallenge payload too big.\n");
+		rv = 0;
+		goto fail;
+	}
+
+	peers_ch = kmalloc(p.length, GFP_NOIO);
+	if (peers_ch == NULL) {
+		dev_err(DEV, "kmalloc of peers_ch failed\n");
+		rv = 0;
+		goto fail;
+	}
+
+	rv = drbd_recv(mdev, peers_ch, p.length);
+
+	if (rv != p.length) {
+		dev_err(DEV, "short read AuthChallenge: l=%u\n", rv);
+		rv = 0;
+		goto fail;
+	}
+
+	resp_size = crypto_hash_digestsize(mdev->cram_hmac_tfm);
+	response = kmalloc(resp_size, GFP_NOIO);
+	if (response == NULL) {
+		dev_err(DEV, "kmalloc of response failed\n");
+		rv = 0;
+		goto fail;
+	}
+
+	sg_init_table(&sg, 1);
+	sg_set_buf(&sg, peers_ch, p.length);
+
+	rv = crypto_hash_digest(&desc, &sg, sg.length, response);
+	if (rv) {
+		dev_err(DEV, "crypto_hash_digest() failed with %d\n", rv);
+		rv = 0;
+		goto fail;
+	}
+
+	rv = drbd_send_cmd2(mdev, P_AUTH_RESPONSE, response, resp_size);
+	if (!rv)
+		goto fail;
+
+	rv = drbd_recv_header(mdev, &p);
+	if (!rv)
+		goto fail;
+
+	if (p.command != P_AUTH_RESPONSE) {
+		dev_err(DEV, "expected AuthResponse packet, received: %s (0x%04x)\n",
+		    cmdname(p.command), p.command);
+		rv = 0;
+		goto fail;
+	}
+
+	if (p.length != resp_size) {
+		dev_err(DEV, "expected AuthResponse payload of wrong size\n");
+		rv = 0;
+		goto fail;
+	}
+
+	rv = drbd_recv(mdev, response , resp_size);
+
+	if (rv != resp_size) {
+		dev_err(DEV, "short read receiving AuthResponse: l=%u\n", rv);
+		rv = 0;
+		goto fail;
+	}
+
+	right_response = kmalloc(resp_size, GFP_NOIO);
+	if (response == NULL) {
+		dev_err(DEV, "kmalloc of right_response failed\n");
+		rv = 0;
+		goto fail;
+	}
+
+	sg_set_buf(&sg, my_challenge, CHALLENGE_LEN);
+
+	rv = crypto_hash_digest(&desc, &sg, sg.length, right_response);
+	if (rv) {
+		dev_err(DEV, "crypto_hash_digest() failed with %d\n", rv);
+		rv = 0;
+		goto fail;
+	}
+
+	rv = !memcmp(response, right_response, resp_size);
+
+	if (rv)
+		dev_info(DEV, "Peer authenticated using %d bytes of '%s' HMAC\n",
+		     resp_size, mdev->net_conf->cram_hmac_alg);
+
+ fail:
+	kfree(peers_ch);
+	kfree(response);
+	kfree(right_response);
+
+	return rv;
+}
+#endif
+
+int drbdd_init(struct drbd_thread *thi)
+{
+	struct drbd_conf *mdev = thi->mdev;
+	unsigned int minor = mdev_to_minor(mdev);
+	int h;
+
+	sprintf(current->comm, "drbd%d_receiver", minor);
+
+	dev_info(DEV, "receiver (re)started\n");
+
+	do {
+		h = drbd_connect(mdev);
+		if (h == 0) {
+			drbd_disconnect(mdev);
+			__set_current_state(TASK_INTERRUPTIBLE);
+			schedule_timeout(HZ);
+		}
+		if (h == -1) {
+			dev_warn(DEV, "Discarding network configuration.\n");
+			drbd_force_state(mdev, NS(conn, C_DISCONNECTING));
+		}
+	} while (h == 0);
+
+	if (h > 0) {
+		if (get_net_conf(mdev)) {
+			drbdd(mdev);
+			put_net_conf(mdev);
+		}
+	}
+
+	drbd_disconnect(mdev);
+
+	dev_info(DEV, "receiver terminated\n");
+	return 0;
+}
+
+/* ********* acknowledge sender ******** */
+
+static int got_RqSReply(struct drbd_conf *mdev, struct p_header *h)
+{
+	struct p_req_state_reply *p = (struct p_req_state_reply *)h;
+
+	int retcode = be32_to_cpu(p->retcode);
+
+	if (retcode >= SS_SUCCESS) {
+		set_bit(CL_ST_CHG_SUCCESS, &mdev->flags);
+	} else {
+		set_bit(CL_ST_CHG_FAIL, &mdev->flags);
+		dev_err(DEV, "Requested state change failed by peer: %s (%d)\n",
+		    drbd_set_st_err_str(retcode), retcode);
+	}
+	wake_up(&mdev->state_wait);
+
+	return TRUE;
+}
+
+static int got_Ping(struct drbd_conf *mdev, struct p_header *h)
+{
+	return drbd_send_ping_ack(mdev);
+
+}
+
+static int got_PingAck(struct drbd_conf *mdev, struct p_header *h)
+{
+	/* restore idle timeout */
+	mdev->meta.socket->sk->sk_rcvtimeo = mdev->net_conf->ping_int*HZ;
+
+	return TRUE;
+}
+
+static int got_IsInSync(struct drbd_conf *mdev, struct p_header *h)
+{
+	struct p_block_ack *p = (struct p_block_ack *)h;
+	sector_t sector = be64_to_cpu(p->sector);
+	int blksize = be32_to_cpu(p->blksize);
+
+	D_ASSERT(mdev->agreed_pro_version >= 89);
+
+	update_peer_seq(mdev, be32_to_cpu(p->seq_num));
+
+	drbd_rs_complete_io(mdev, sector);
+	drbd_set_in_sync(mdev, sector, blksize);
+	/* rs_same_csums is supposed to count in units of BM_BLOCK_SIZE */
+	mdev->rs_same_csum += (blksize >> BM_BLOCK_SHIFT);
+	dec_rs_pending(mdev);
+
+	return TRUE;
+}
+
+/* when we receive the ACK for a write request,
+ * verify that we actually know about it */
+static struct drbd_request *_ack_id_to_req(struct drbd_conf *mdev,
+	u64 id, sector_t sector)
+{
+	struct hlist_head *slot = tl_hash_slot(mdev, sector);
+	struct hlist_node *n;
+	struct drbd_request *req;
+
+	hlist_for_each_entry(req, n, slot, colision) {
+		if ((unsigned long)req == (unsigned long)id) {
+			if (req->sector != sector) {
+				dev_err(DEV, "_ack_id_to_req: found req %p but it has "
+				    "wrong sector (%llus versus %llus)\n", req,
+				    (unsigned long long)req->sector,
+				    (unsigned long long)sector);
+				break;
+			}
+			return req;
+		}
+	}
+	dev_err(DEV, "_ack_id_to_req: failed to find req %p, sector %llus in list\n",
+		(void *)(unsigned long)id, (unsigned long long)sector);
+	return NULL;
+}
+
+typedef struct drbd_request *(req_validator_fn)
+	(struct drbd_conf *mdev, u64 id, sector_t sector);
+
+static int validate_req_change_req_state(struct drbd_conf *mdev,
+	u64 id, sector_t sector, req_validator_fn validator,
+	const char *func, enum drbd_req_event what)
+{
+	struct drbd_request *req;
+	struct bio_and_error m;
+
+	spin_lock_irq(&mdev->req_lock);
+	req = validator(mdev, id, sector);
+	if (unlikely(!req)) {
+		spin_unlock_irq(&mdev->req_lock);
+		dev_err(DEV, "%s: got a corrupt block_id/sector pair\n", func);
+		return FALSE;
+	}
+	__req_mod(req, what, &m);
+	spin_unlock_irq(&mdev->req_lock);
+
+	if (m.bio)
+		complete_master_bio(mdev, &m);
+	return TRUE;
+}
+
+static int got_BlockAck(struct drbd_conf *mdev, struct p_header *h)
+{
+	struct p_block_ack *p = (struct p_block_ack *)h;
+	sector_t sector = be64_to_cpu(p->sector);
+	int blksize = be32_to_cpu(p->blksize);
+	enum drbd_req_event what;
+
+	update_peer_seq(mdev, be32_to_cpu(p->seq_num));
+
+	if (is_syncer_block_id(p->block_id)) {
+		drbd_set_in_sync(mdev, sector, blksize);
+		dec_rs_pending(mdev);
+		return TRUE;
+	}
+	switch (be16_to_cpu(h->command)) {
+	case P_RS_WRITE_ACK:
+		D_ASSERT(mdev->net_conf->wire_protocol == DRBD_PROT_C);
+		what = write_acked_by_peer_and_sis;
+		break;
+	case P_WRITE_ACK:
+		D_ASSERT(mdev->net_conf->wire_protocol == DRBD_PROT_C);
+		what = write_acked_by_peer;
+		break;
+	case P_RECV_ACK:
+		D_ASSERT(mdev->net_conf->wire_protocol == DRBD_PROT_B);
+		what = recv_acked_by_peer;
+		break;
+	case P_DISCARD_ACK:
+		D_ASSERT(mdev->net_conf->wire_protocol == DRBD_PROT_C);
+		what = conflict_discarded_by_peer;
+		break;
+	default:
+		D_ASSERT(0);
+		return FALSE;
+	}
+
+	return validate_req_change_req_state(mdev, p->block_id, sector,
+		_ack_id_to_req, __func__ , what);
+}
+
+static int got_NegAck(struct drbd_conf *mdev, struct p_header *h)
+{
+	struct p_block_ack *p = (struct p_block_ack *)h;
+	sector_t sector = be64_to_cpu(p->sector);
+
+	if (__ratelimit(&drbd_ratelimit_state))
+		dev_warn(DEV, "Got NegAck packet. Peer is in troubles?\n");
+
+	update_peer_seq(mdev, be32_to_cpu(p->seq_num));
+
+	if (is_syncer_block_id(p->block_id)) {
+		int size = be32_to_cpu(p->blksize);
+		dec_rs_pending(mdev);
+		drbd_rs_failed_io(mdev, sector, size);
+		return TRUE;
+	}
+	return validate_req_change_req_state(mdev, p->block_id, sector,
+		_ack_id_to_req, __func__ , neg_acked);
+}
+
+static int got_NegDReply(struct drbd_conf *mdev, struct p_header *h)
+{
+	struct p_block_ack *p = (struct p_block_ack *)h;
+	sector_t sector = be64_to_cpu(p->sector);
+
+	update_peer_seq(mdev, be32_to_cpu(p->seq_num));
+	dev_err(DEV, "Got NegDReply; Sector %llus, len %u; Fail original request.\n",
+	    (unsigned long long)sector, be32_to_cpu(p->blksize));
+
+	return validate_req_change_req_state(mdev, p->block_id, sector,
+		_ar_id_to_req, __func__ , neg_acked);
+}
+
+static int got_NegRSDReply(struct drbd_conf *mdev, struct p_header *h)
+{
+	sector_t sector;
+	int size;
+	struct p_block_ack *p = (struct p_block_ack *)h;
+
+	sector = be64_to_cpu(p->sector);
+	size = be32_to_cpu(p->blksize);
+	D_ASSERT(p->block_id == ID_SYNCER);
+
+	update_peer_seq(mdev, be32_to_cpu(p->seq_num));
+
+	dec_rs_pending(mdev);
+
+	if (get_ldev_if_state(mdev, D_FAILED)) {
+		drbd_rs_complete_io(mdev, sector);
+		drbd_rs_failed_io(mdev, sector, size);
+		put_ldev(mdev);
+	}
+
+	return TRUE;
+}
+
+static int got_BarrierAck(struct drbd_conf *mdev, struct p_header *h)
+{
+	struct p_barrier_ack *p = (struct p_barrier_ack *)h;
+
+	tl_release(mdev, p->barrier, be32_to_cpu(p->set_size));
+
+	return TRUE;
+}
+
+static int got_OVResult(struct drbd_conf *mdev, struct p_header *h)
+{
+	struct p_block_ack *p = (struct p_block_ack *)h;
+	struct drbd_work *w;
+	sector_t sector;
+	int size;
+
+	sector = be64_to_cpu(p->sector);
+	size = be32_to_cpu(p->blksize);
+
+	update_peer_seq(mdev, be32_to_cpu(p->seq_num));
+
+	if (be64_to_cpu(p->block_id) == ID_OUT_OF_SYNC)
+		drbd_ov_oos_found(mdev, sector, size);
+	else
+		ov_oos_print(mdev);
+
+	drbd_rs_complete_io(mdev, sector);
+	dec_rs_pending(mdev);
+
+	if (--mdev->ov_left == 0) {
+		w = kmalloc(sizeof(*w), GFP_NOIO);
+		if (w) {
+			w->cb = w_ov_finished;
+			drbd_queue_work_front(&mdev->data.work, w);
+		} else {
+			dev_err(DEV, "kmalloc(w) failed.");
+			ov_oos_print(mdev);
+			drbd_resync_finished(mdev);
+		}
+	}
+	return TRUE;
+}
+
+struct asender_cmd {
+	size_t pkt_size;
+	int (*process)(struct drbd_conf *mdev, struct p_header *h);
+};
+
+static struct asender_cmd *get_asender_cmd(int cmd)
+{
+	static struct asender_cmd asender_tbl[] = {
+		/* anything missing from this table is in
+		 * the drbd_cmd_handler (drbd_default_handler) table,
+		 * see the beginning of drbdd() */
+	[P_PING]	    = { sizeof(struct p_header), got_Ping },
+	[P_PING_ACK]	    = { sizeof(struct p_header), got_PingAck },
+	[P_RECV_ACK]	    = { sizeof(struct p_block_ack), got_BlockAck },
+	[P_WRITE_ACK]	    = { sizeof(struct p_block_ack), got_BlockAck },
+	[P_RS_WRITE_ACK]    = { sizeof(struct p_block_ack), got_BlockAck },
+	[P_DISCARD_ACK]	    = { sizeof(struct p_block_ack), got_BlockAck },
+	[P_NEG_ACK]	    = { sizeof(struct p_block_ack), got_NegAck },
+	[P_NEG_DREPLY]	    = { sizeof(struct p_block_ack), got_NegDReply },
+	[P_NEG_RS_DREPLY]   = { sizeof(struct p_block_ack), got_NegRSDReply},
+	[P_OV_RESULT]	    = { sizeof(struct p_block_ack), got_OVResult },
+	[P_BARRIER_ACK]	    = { sizeof(struct p_barrier_ack), got_BarrierAck },
+	[P_STATE_CHG_REPLY] = { sizeof(struct p_req_state_reply), got_RqSReply },
+	[P_RS_IS_IN_SYNC]   = { sizeof(struct p_block_ack), got_IsInSync },
+	[P_MAX_CMD]	    = { 0, NULL },
+	};
+	if (cmd > P_MAX_CMD || asender_tbl[cmd].process == NULL)
+		return NULL;
+	return &asender_tbl[cmd];
+}
+
+int drbd_asender(struct drbd_thread *thi)
+{
+	struct drbd_conf *mdev = thi->mdev;
+	struct p_header *h = &mdev->meta.rbuf.header;
+	struct asender_cmd *cmd = NULL;
+
+	int rv, len;
+	void *buf    = h;
+	int received = 0;
+	int expect   = sizeof(struct p_header);
+	int empty;
+
+	sprintf(current->comm, "drbd%d_asender", mdev_to_minor(mdev));
+
+	current->policy = SCHED_RR;  /* Make this a realtime task! */
+	current->rt_priority = 2;    /* more important than all other tasks */
+
+	while (get_t_state(thi) == Running) {
+		drbd_thread_current_set_cpu(mdev);
+		if (test_and_clear_bit(SEND_PING, &mdev->flags)) {
+			ERR_IF(!drbd_send_ping(mdev)) goto reconnect;
+			mdev->meta.socket->sk->sk_rcvtimeo =
+				mdev->net_conf->ping_timeo*HZ/10;
+		}
+
+		/* conditionally cork;
+		 * it may hurt latency if we cork without much to send */
+		if (!mdev->net_conf->no_cork &&
+			3 < atomic_read(&mdev->unacked_cnt))
+			drbd_tcp_cork(mdev->meta.socket);
+		while (1) {
+			clear_bit(SIGNAL_ASENDER, &mdev->flags);
+			flush_signals(current);
+			if (!drbd_process_done_ee(mdev)) {
+				dev_err(DEV, "process_done_ee() = NOT_OK\n");
+				goto reconnect;
+			}
+			/* to avoid race with newly queued ACKs */
+			set_bit(SIGNAL_ASENDER, &mdev->flags);
+			spin_lock_irq(&mdev->req_lock);
+			empty = list_empty(&mdev->done_ee);
+			spin_unlock_irq(&mdev->req_lock);
+			/* new ack may have been queued right here,
+			 * but then there is also a signal pending,
+			 * and we start over... */
+			if (empty)
+				break;
+		}
+		/* but unconditionally uncork unless disabled */
+		if (!mdev->net_conf->no_cork)
+			drbd_tcp_uncork(mdev->meta.socket);
+
+		/* short circuit, recv_msg would return EINTR anyways. */
+		if (signal_pending(current))
+			continue;
+
+		rv = drbd_recv_short(mdev, mdev->meta.socket,
+				     buf, expect-received, 0);
+		clear_bit(SIGNAL_ASENDER, &mdev->flags);
+
+		flush_signals(current);
+
+		/* Note:
+		 * -EINTR	 (on meta) we got a signal
+		 * -EAGAIN	 (on meta) rcvtimeo expired
+		 * -ECONNRESET	 other side closed the connection
+		 * -ERESTARTSYS  (on data) we got a signal
+		 * rv <  0	 other than above: unexpected error!
+		 * rv == expected: full header or command
+		 * rv <  expected: "woken" by signal during receive
+		 * rv == 0	 : "connection shut down by peer"
+		 */
+		if (likely(rv > 0)) {
+			received += rv;
+			buf	 += rv;
+		} else if (rv == 0) {
+			dev_err(DEV, "meta connection shut down by peer.\n");
+			goto reconnect;
+		} else if (rv == -EAGAIN) {
+			if (mdev->meta.socket->sk->sk_rcvtimeo ==
+			    mdev->net_conf->ping_timeo*HZ/10) {
+				dev_err(DEV, "PingAck did not arrive in time.\n");
+				goto reconnect;
+			}
+			set_bit(SEND_PING, &mdev->flags);
+			continue;
+		} else if (rv == -EINTR) {
+			continue;
+		} else {
+			dev_err(DEV, "sock_recvmsg returned %d\n", rv);
+			goto reconnect;
+		}
+
+		if (received == expect && cmd == NULL) {
+			if (unlikely(h->magic != BE_DRBD_MAGIC)) {
+				dev_err(DEV, "magic?? on meta m: 0x%lx c: %d l: %d\n",
+				    (long)be32_to_cpu(h->magic),
+				    h->command, h->length);
+				goto reconnect;
+			}
+			cmd = get_asender_cmd(be16_to_cpu(h->command));
+			len = be16_to_cpu(h->length);
+			if (unlikely(cmd == NULL)) {
+				dev_err(DEV, "unknown command?? on meta m: 0x%lx c: %d l: %d\n",
+				    (long)be32_to_cpu(h->magic),
+				    h->command, h->length);
+				goto disconnect;
+			}
+			expect = cmd->pkt_size;
+			ERR_IF(len != expect-sizeof(struct p_header)) {
+				trace_drbd_packet(mdev, mdev->meta.socket, 1, (void *)h, __FILE__, __LINE__);
+				goto reconnect;
+			}
+		}
+		if (received == expect) {
+			D_ASSERT(cmd != NULL);
+			trace_drbd_packet(mdev, mdev->meta.socket, 1, (void *)h, __FILE__, __LINE__);
+			if (!cmd->process(mdev, h))
+				goto reconnect;
+
+			buf	 = h;
+			received = 0;
+			expect	 = sizeof(struct p_header);
+			cmd	 = NULL;
+		}
+	}
+
+	if (0) {
+reconnect:
+		drbd_force_state(mdev, NS(conn, C_NETWORK_FAILURE));
+	}
+	if (0) {
+disconnect:
+		drbd_force_state(mdev, NS(conn, C_DISCONNECTING));
+	}
+	clear_bit(SIGNAL_ASENDER, &mdev->flags);
+
+	D_ASSERT(mdev->state.conn < C_CONNECTED);
+	dev_info(DEV, "asender terminated\n");
+
+	return 0;
+}
diff --git a/drivers/block/drbd/drbd_req.c b/drivers/block/drbd/drbd_req.c
new file mode 100644
index 00000000000..0656cf1edd5
--- /dev/null
+++ b/drivers/block/drbd/drbd_req.c
@@ -0,0 +1,1132 @@
+/*
+   drbd_req.c
+
+   This file is part of DRBD by Philipp Reisner and Lars Ellenberg.
+
+   Copyright (C) 2001-2008, LINBIT Information Technologies GmbH.
+   Copyright (C) 1999-2008, Philipp Reisner <philipp.reisner@linbit.com>.
+   Copyright (C) 2002-2008, Lars Ellenberg <lars.ellenberg@linbit.com>.
+
+   drbd is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 2, or (at your option)
+   any later version.
+
+   drbd is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with drbd; see the file COPYING.  If not, write to
+   the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
+
+ */
+
+#include <linux/autoconf.h>
+#include <linux/module.h>
+
+#include <linux/slab.h>
+#include <linux/drbd.h>
+#include "drbd_int.h"
+#include "drbd_tracing.h"
+#include "drbd_req.h"
+
+
+/* Update disk stats at start of I/O request */
+static void _drbd_start_io_acct(struct drbd_conf *mdev, struct drbd_request *req, struct bio *bio)
+{
+	const int rw = bio_data_dir(bio);
+	int cpu;
+	cpu = part_stat_lock();
+	part_stat_inc(cpu, &mdev->vdisk->part0, ios[rw]);
+	part_stat_add(cpu, &mdev->vdisk->part0, sectors[rw], bio_sectors(bio));
+	part_stat_unlock();
+	mdev->vdisk->part0.in_flight[rw]++;
+}
+
+/* Update disk stats when completing request upwards */
+static void _drbd_end_io_acct(struct drbd_conf *mdev, struct drbd_request *req)
+{
+	int rw = bio_data_dir(req->master_bio);
+	unsigned long duration = jiffies - req->start_time;
+	int cpu;
+	cpu = part_stat_lock();
+	part_stat_add(cpu, &mdev->vdisk->part0, ticks[rw], duration);
+	part_round_stats(cpu, &mdev->vdisk->part0);
+	part_stat_unlock();
+	mdev->vdisk->part0.in_flight[rw]--;
+}
+
+static void _req_is_done(struct drbd_conf *mdev, struct drbd_request *req, const int rw)
+{
+	const unsigned long s = req->rq_state;
+	/* if it was a write, we may have to set the corresponding
+	 * bit(s) out-of-sync first. If it had a local part, we need to
+	 * release the reference to the activity log. */
+	if (rw == WRITE) {
+		/* remove it from the transfer log.
+		 * well, only if it had been there in the first
+		 * place... if it had not (local only or conflicting
+		 * and never sent), it should still be "empty" as
+		 * initialized in drbd_req_new(), so we can list_del() it
+		 * here unconditionally */
+		list_del(&req->tl_requests);
+		/* Set out-of-sync unless both OK flags are set
+		 * (local only or remote failed).
+		 * Other places where we set out-of-sync:
+		 * READ with local io-error */
+		if (!(s & RQ_NET_OK) || !(s & RQ_LOCAL_OK))
+			drbd_set_out_of_sync(mdev, req->sector, req->size);
+
+		if ((s & RQ_NET_OK) && (s & RQ_LOCAL_OK) && (s & RQ_NET_SIS))
+			drbd_set_in_sync(mdev, req->sector, req->size);
+
+		/* one might be tempted to move the drbd_al_complete_io
+		 * to the local io completion callback drbd_endio_pri.
+		 * but, if this was a mirror write, we may only
+		 * drbd_al_complete_io after this is RQ_NET_DONE,
+		 * otherwise the extent could be dropped from the al
+		 * before it has actually been written on the peer.
+		 * if we crash before our peer knows about the request,
+		 * but after the extent has been dropped from the al,
+		 * we would forget to resync the corresponding extent.
+		 */
+		if (s & RQ_LOCAL_MASK) {
+			if (get_ldev_if_state(mdev, D_FAILED)) {
+				drbd_al_complete_io(mdev, req->sector);
+				put_ldev(mdev);
+			} else if (__ratelimit(&drbd_ratelimit_state)) {
+				dev_warn(DEV, "Should have called drbd_al_complete_io(, %llu), "
+				     "but my Disk seems to have failed :(\n",
+				     (unsigned long long) req->sector);
+			}
+		}
+	}
+
+	/* if it was a local io error, we want to notify our
+	 * peer about that, and see if we need to
+	 * detach the disk and stuff.
+	 * to avoid allocating some special work
+	 * struct, reuse the request. */
+
+	/* THINK
+	 * why do we do this not when we detect the error,
+	 * but delay it until it is "done", i.e. possibly
+	 * until the next barrier ack? */
+
+	if (rw == WRITE &&
+	    ((s & RQ_LOCAL_MASK) && !(s & RQ_LOCAL_OK))) {
+		if (!(req->w.list.next == LIST_POISON1 ||
+		      list_empty(&req->w.list))) {
+			/* DEBUG ASSERT only; if this triggers, we
+			 * probably corrupt the worker list here */
+			dev_err(DEV, "req->w.list.next = %p\n", req->w.list.next);
+			dev_err(DEV, "req->w.list.prev = %p\n", req->w.list.prev);
+		}
+		req->w.cb = w_io_error;
+		drbd_queue_work(&mdev->data.work, &req->w);
+		/* drbd_req_free() is done in w_io_error */
+	} else {
+		drbd_req_free(req);
+	}
+}
+
+static void queue_barrier(struct drbd_conf *mdev)
+{
+	struct drbd_tl_epoch *b;
+
+	/* We are within the req_lock. Once we queued the barrier for sending,
+	 * we set the CREATE_BARRIER bit. It is cleared as soon as a new
+	 * barrier/epoch object is added. This is the only place this bit is
+	 * set. It indicates that the barrier for this epoch is already queued,
+	 * and no new epoch has been created yet. */
+	if (test_bit(CREATE_BARRIER, &mdev->flags))
+		return;
+
+	b = mdev->newest_tle;
+	b->w.cb = w_send_barrier;
+	/* inc_ap_pending done here, so we won't
+	 * get imbalanced on connection loss.
+	 * dec_ap_pending will be done in got_BarrierAck
+	 * or (on connection loss) in tl_clear.  */
+	inc_ap_pending(mdev);
+	drbd_queue_work(&mdev->data.work, &b->w);
+	set_bit(CREATE_BARRIER, &mdev->flags);
+}
+
+static void _about_to_complete_local_write(struct drbd_conf *mdev,
+	struct drbd_request *req)
+{
+	const unsigned long s = req->rq_state;
+	struct drbd_request *i;
+	struct drbd_epoch_entry *e;
+	struct hlist_node *n;
+	struct hlist_head *slot;
+
+	/* before we can signal completion to the upper layers,
+	 * we may need to close the current epoch */
+	if (mdev->state.conn >= C_CONNECTED &&
+	    req->epoch == mdev->newest_tle->br_number)
+		queue_barrier(mdev);
+
+	/* we need to do the conflict detection stuff,
+	 * if we have the ee_hash (two_primaries) and
+	 * this has been on the network */
+	if ((s & RQ_NET_DONE) && mdev->ee_hash != NULL) {
+		const sector_t sector = req->sector;
+		const int size = req->size;
+
+		/* ASSERT:
+		 * there must be no conflicting requests, since
+		 * they must have been failed on the spot */
+#define OVERLAPS overlaps(sector, size, i->sector, i->size)
+		slot = tl_hash_slot(mdev, sector);
+		hlist_for_each_entry(i, n, slot, colision) {
+			if (OVERLAPS) {
+				dev_alert(DEV, "LOGIC BUG: completed: %p %llus +%u; "
+				      "other: %p %llus +%u\n",
+				      req, (unsigned long long)sector, size,
+				      i, (unsigned long long)i->sector, i->size);
+			}
+		}
+
+		/* maybe "wake" those conflicting epoch entries
+		 * that wait for this request to finish.
+		 *
+		 * currently, there can be only _one_ such ee
+		 * (well, or some more, which would be pending
+		 * P_DISCARD_ACK not yet sent by the asender...),
+		 * since we block the receiver thread upon the
+		 * first conflict detection, which will wait on
+		 * misc_wait.  maybe we want to assert that?
+		 *
+		 * anyways, if we found one,
+		 * we just have to do a wake_up.  */
+#undef OVERLAPS
+#define OVERLAPS overlaps(sector, size, e->sector, e->size)
+		slot = ee_hash_slot(mdev, req->sector);
+		hlist_for_each_entry(e, n, slot, colision) {
+			if (OVERLAPS) {
+				wake_up(&mdev->misc_wait);
+				break;
+			}
+		}
+	}
+#undef OVERLAPS
+}
+
+void complete_master_bio(struct drbd_conf *mdev,
+		struct bio_and_error *m)
+{
+	trace_drbd_bio(mdev, "Rq", m->bio, 1, NULL);
+	bio_endio(m->bio, m->error);
+	dec_ap_bio(mdev);
+}
+
+/* Helper for __req_mod().
+ * Set m->bio to the master bio, if it is fit to be completed,
+ * or leave it alone (it is initialized to NULL in __req_mod),
+ * if it has already been completed, or cannot be completed yet.
+ * If m->bio is set, the error status to be returned is placed in m->error.
+ */
+void _req_may_be_done(struct drbd_request *req, struct bio_and_error *m)
+{
+	const unsigned long s = req->rq_state;
+	struct drbd_conf *mdev = req->mdev;
+	/* only WRITES may end up here without a master bio (on barrier ack) */
+	int rw = req->master_bio ? bio_data_dir(req->master_bio) : WRITE;
+
+	trace_drbd_req(req, nothing, "_req_may_be_done");
+
+	/* we must not complete the master bio, while it is
+	 *	still being processed by _drbd_send_zc_bio (drbd_send_dblock)
+	 *	not yet acknowledged by the peer
+	 *	not yet completed by the local io subsystem
+	 * these flags may get cleared in any order by
+	 *	the worker,
+	 *	the receiver,
+	 *	the bio_endio completion callbacks.
+	 */
+	if (s & RQ_NET_QUEUED)
+		return;
+	if (s & RQ_NET_PENDING)
+		return;
+	if (s & RQ_LOCAL_PENDING)
+		return;
+
+	if (req->master_bio) {
+		/* this is data_received (remote read)
+		 * or protocol C P_WRITE_ACK
+		 * or protocol B P_RECV_ACK
+		 * or protocol A "handed_over_to_network" (SendAck)
+		 * or canceled or failed,
+		 * or killed from the transfer log due to connection loss.
+		 */
+
+		/*
+		 * figure out whether to report success or failure.
+		 *
+		 * report success when at least one of the operations succeeded.
+		 * or, to put the other way,
+		 * only report failure, when both operations failed.
+		 *
+		 * what to do about the failures is handled elsewhere.
+		 * what we need to do here is just: complete the master_bio.
+		 *
+		 * local completion error, if any, has been stored as ERR_PTR
+		 * in private_bio within drbd_endio_pri.
+		 */
+		int ok = (s & RQ_LOCAL_OK) || (s & RQ_NET_OK);
+		int error = PTR_ERR(req->private_bio);
+
+		/* remove the request from the conflict detection
+		 * respective block_id verification hash */
+		if (!hlist_unhashed(&req->colision))
+			hlist_del(&req->colision);
+		else
+			D_ASSERT((s & RQ_NET_MASK) == 0);
+
+		/* for writes we need to do some extra housekeeping */
+		if (rw == WRITE)
+			_about_to_complete_local_write(mdev, req);
+
+		/* Update disk stats */
+		_drbd_end_io_acct(mdev, req);
+
+		m->error = ok ? 0 : (error ?: -EIO);
+		m->bio = req->master_bio;
+		req->master_bio = NULL;
+	}
+
+	if ((s & RQ_NET_MASK) == 0 || (s & RQ_NET_DONE)) {
+		/* this is disconnected (local only) operation,
+		 * or protocol C P_WRITE_ACK,
+		 * or protocol A or B P_BARRIER_ACK,
+		 * or killed from the transfer log due to connection loss. */
+		_req_is_done(mdev, req, rw);
+	}
+	/* else: network part and not DONE yet. that is
+	 * protocol A or B, barrier ack still pending... */
+}
+
+/*
+ * checks whether there was an overlapping request
+ * or ee already registered.
+ *
+ * if so, return 1, in which case this request is completed on the spot,
+ * without ever being submitted or send.
+ *
+ * return 0 if it is ok to submit this request.
+ *
+ * NOTE:
+ * paranoia: assume something above us is broken, and issues different write
+ * requests for the same block simultaneously...
+ *
+ * To ensure these won't be reordered differently on both nodes, resulting in
+ * diverging data sets, we discard the later one(s). Not that this is supposed
+ * to happen, but this is the rationale why we also have to check for
+ * conflicting requests with local origin, and why we have to do so regardless
+ * of whether we allowed multiple primaries.
+ *
+ * BTW, in case we only have one primary, the ee_hash is empty anyways, and the
+ * second hlist_for_each_entry becomes a noop. This is even simpler than to
+ * grab a reference on the net_conf, and check for the two_primaries flag...
+ */
+static int _req_conflicts(struct drbd_request *req)
+{
+	struct drbd_conf *mdev = req->mdev;
+	const sector_t sector = req->sector;
+	const int size = req->size;
+	struct drbd_request *i;
+	struct drbd_epoch_entry *e;
+	struct hlist_node *n;
+	struct hlist_head *slot;
+
+	D_ASSERT(hlist_unhashed(&req->colision));
+
+	if (!get_net_conf(mdev))
+		return 0;
+
+	/* BUG_ON */
+	ERR_IF (mdev->tl_hash_s == 0)
+		goto out_no_conflict;
+	BUG_ON(mdev->tl_hash == NULL);
+
+#define OVERLAPS overlaps(i->sector, i->size, sector, size)
+	slot = tl_hash_slot(mdev, sector);
+	hlist_for_each_entry(i, n, slot, colision) {
+		if (OVERLAPS) {
+			dev_alert(DEV, "%s[%u] Concurrent local write detected! "
+			      "[DISCARD L] new: %llus +%u; "
+			      "pending: %llus +%u\n",
+			      current->comm, current->pid,
+			      (unsigned long long)sector, size,
+			      (unsigned long long)i->sector, i->size);
+			goto out_conflict;
+		}
+	}
+
+	if (mdev->ee_hash_s) {
+		/* now, check for overlapping requests with remote origin */
+		BUG_ON(mdev->ee_hash == NULL);
+#undef OVERLAPS
+#define OVERLAPS overlaps(e->sector, e->size, sector, size)
+		slot = ee_hash_slot(mdev, sector);
+		hlist_for_each_entry(e, n, slot, colision) {
+			if (OVERLAPS) {
+				dev_alert(DEV, "%s[%u] Concurrent remote write detected!"
+				      " [DISCARD L] new: %llus +%u; "
+				      "pending: %llus +%u\n",
+				      current->comm, current->pid,
+				      (unsigned long long)sector, size,
+				      (unsigned long long)e->sector, e->size);
+				goto out_conflict;
+			}
+		}
+	}
+#undef OVERLAPS
+
+out_no_conflict:
+	/* this is like it should be, and what we expected.
+	 * our users do behave after all... */
+	put_net_conf(mdev);
+	return 0;
+
+out_conflict:
+	put_net_conf(mdev);
+	return 1;
+}
+
+/* obviously this could be coded as many single functions
+ * instead of one huge switch,
+ * or by putting the code directly in the respective locations
+ * (as it has been before).
+ *
+ * but having it this way
+ *  enforces that it is all in this one place, where it is easier to audit,
+ *  it makes it obvious that whatever "event" "happens" to a request should
+ *  happen "atomically" within the req_lock,
+ *  and it enforces that we have to think in a very structured manner
+ *  about the "events" that may happen to a request during its life time ...
+ */
+void __req_mod(struct drbd_request *req, enum drbd_req_event what,
+		struct bio_and_error *m)
+{
+	struct drbd_conf *mdev = req->mdev;
+	m->bio = NULL;
+
+	trace_drbd_req(req, what, NULL);
+
+	switch (what) {
+	default:
+		dev_err(DEV, "LOGIC BUG in %s:%u\n", __FILE__ , __LINE__);
+		break;
+
+	/* does not happen...
+	 * initialization done in drbd_req_new
+	case created:
+		break;
+		*/
+
+	case to_be_send: /* via network */
+		/* reached via drbd_make_request_common
+		 * and from w_read_retry_remote */
+		D_ASSERT(!(req->rq_state & RQ_NET_MASK));
+		req->rq_state |= RQ_NET_PENDING;
+		inc_ap_pending(mdev);
+		break;
+
+	case to_be_submitted: /* locally */
+		/* reached via drbd_make_request_common */
+		D_ASSERT(!(req->rq_state & RQ_LOCAL_MASK));
+		req->rq_state |= RQ_LOCAL_PENDING;
+		break;
+
+	case completed_ok:
+		if (bio_data_dir(req->master_bio) == WRITE)
+			mdev->writ_cnt += req->size>>9;
+		else
+			mdev->read_cnt += req->size>>9;
+
+		req->rq_state |= (RQ_LOCAL_COMPLETED|RQ_LOCAL_OK);
+		req->rq_state &= ~RQ_LOCAL_PENDING;
+
+		_req_may_be_done(req, m);
+		put_ldev(mdev);
+		break;
+
+	case write_completed_with_error:
+		req->rq_state |= RQ_LOCAL_COMPLETED;
+		req->rq_state &= ~RQ_LOCAL_PENDING;
+
+		dev_alert(DEV, "Local WRITE failed sec=%llus size=%u\n",
+		      (unsigned long long)req->sector, req->size);
+		/* and now: check how to handle local io error. */
+		__drbd_chk_io_error(mdev, FALSE);
+		_req_may_be_done(req, m);
+		put_ldev(mdev);
+		break;
+
+	case read_ahead_completed_with_error:
+		/* it is legal to fail READA */
+		req->rq_state |= RQ_LOCAL_COMPLETED;
+		req->rq_state &= ~RQ_LOCAL_PENDING;
+		_req_may_be_done(req, m);
+		put_ldev(mdev);
+		break;
+
+	case read_completed_with_error:
+		drbd_set_out_of_sync(mdev, req->sector, req->size);
+
+		req->rq_state |= RQ_LOCAL_COMPLETED;
+		req->rq_state &= ~RQ_LOCAL_PENDING;
+
+		dev_alert(DEV, "Local READ failed sec=%llus size=%u\n",
+		      (unsigned long long)req->sector, req->size);
+		/* _req_mod(req,to_be_send); oops, recursion... */
+		D_ASSERT(!(req->rq_state & RQ_NET_MASK));
+		req->rq_state |= RQ_NET_PENDING;
+		inc_ap_pending(mdev);
+
+		__drbd_chk_io_error(mdev, FALSE);
+		put_ldev(mdev);
+		/* NOTE: if we have no connection,
+		 * or know the peer has no good data either,
+		 * then we don't actually need to "queue_for_net_read",
+		 * but we do so anyways, since the drbd_io_error()
+		 * and the potential state change to "Diskless"
+		 * needs to be done from process context */
+
+		/* fall through: _req_mod(req,queue_for_net_read); */
+
+	case queue_for_net_read:
+		/* READ or READA, and
+		 * no local disk,
+		 * or target area marked as invalid,
+		 * or just got an io-error. */
+		/* from drbd_make_request_common
+		 * or from bio_endio during read io-error recovery */
+
+		/* so we can verify the handle in the answer packet
+		 * corresponding hlist_del is in _req_may_be_done() */
+		hlist_add_head(&req->colision, ar_hash_slot(mdev, req->sector));
+
+		set_bit(UNPLUG_REMOTE, &mdev->flags); /* why? */
+
+		D_ASSERT(req->rq_state & RQ_NET_PENDING);
+		req->rq_state |= RQ_NET_QUEUED;
+		req->w.cb = (req->rq_state & RQ_LOCAL_MASK)
+			? w_read_retry_remote
+			: w_send_read_req;
+		drbd_queue_work(&mdev->data.work, &req->w);
+		break;
+
+	case queue_for_net_write:
+		/* assert something? */
+		/* from drbd_make_request_common only */
+
+		hlist_add_head(&req->colision, tl_hash_slot(mdev, req->sector));
+		/* corresponding hlist_del is in _req_may_be_done() */
+
+		/* NOTE
+		 * In case the req ended up on the transfer log before being
+		 * queued on the worker, it could lead to this request being
+		 * missed during cleanup after connection loss.
+		 * So we have to do both operations here,
+		 * within the same lock that protects the transfer log.
+		 *
+		 * _req_add_to_epoch(req); this has to be after the
+		 * _maybe_start_new_epoch(req); which happened in
+		 * drbd_make_request_common, because we now may set the bit
+		 * again ourselves to close the current epoch.
+		 *
+		 * Add req to the (now) current epoch (barrier). */
+
+		/* see drbd_make_request_common,
+		 * just after it grabs the req_lock */
+		D_ASSERT(test_bit(CREATE_BARRIER, &mdev->flags) == 0);
+
+		req->epoch = mdev->newest_tle->br_number;
+		list_add_tail(&req->tl_requests,
+				&mdev->newest_tle->requests);
+
+		/* increment size of current epoch */
+		mdev->newest_tle->n_req++;
+
+		/* queue work item to send data */
+		D_ASSERT(req->rq_state & RQ_NET_PENDING);
+		req->rq_state |= RQ_NET_QUEUED;
+		req->w.cb =  w_send_dblock;
+		drbd_queue_work(&mdev->data.work, &req->w);
+
+		/* close the epoch, in case it outgrew the limit */
+		if (mdev->newest_tle->n_req >= mdev->net_conf->max_epoch_size)
+			queue_barrier(mdev);
+
+		break;
+
+	case send_canceled:
+		/* treat it the same */
+	case send_failed:
+		/* real cleanup will be done from tl_clear.  just update flags
+		 * so it is no longer marked as on the worker queue */
+		req->rq_state &= ~RQ_NET_QUEUED;
+		/* if we did it right, tl_clear should be scheduled only after
+		 * this, so this should not be necessary! */
+		_req_may_be_done(req, m);
+		break;
+
+	case handed_over_to_network:
+		/* assert something? */
+		if (bio_data_dir(req->master_bio) == WRITE &&
+		    mdev->net_conf->wire_protocol == DRBD_PROT_A) {
+			/* this is what is dangerous about protocol A:
+			 * pretend it was successfully written on the peer. */
+			if (req->rq_state & RQ_NET_PENDING) {
+				dec_ap_pending(mdev);
+				req->rq_state &= ~RQ_NET_PENDING;
+				req->rq_state |= RQ_NET_OK;
+			} /* else: neg-ack was faster... */
+			/* it is still not yet RQ_NET_DONE until the
+			 * corresponding epoch barrier got acked as well,
+			 * so we know what to dirty on connection loss */
+		}
+		req->rq_state &= ~RQ_NET_QUEUED;
+		req->rq_state |= RQ_NET_SENT;
+		/* because _drbd_send_zc_bio could sleep, and may want to
+		 * dereference the bio even after the "write_acked_by_peer" and
+		 * "completed_ok" events came in, once we return from
+		 * _drbd_send_zc_bio (drbd_send_dblock), we have to check
+		 * whether it is done already, and end it.  */
+		_req_may_be_done(req, m);
+		break;
+
+	case connection_lost_while_pending:
+		/* transfer log cleanup after connection loss */
+		/* assert something? */
+		if (req->rq_state & RQ_NET_PENDING)
+			dec_ap_pending(mdev);
+		req->rq_state &= ~(RQ_NET_OK|RQ_NET_PENDING);
+		req->rq_state |= RQ_NET_DONE;
+		/* if it is still queued, we may not complete it here.
+		 * it will be canceled soon. */
+		if (!(req->rq_state & RQ_NET_QUEUED))
+			_req_may_be_done(req, m);
+		break;
+
+	case write_acked_by_peer_and_sis:
+		req->rq_state |= RQ_NET_SIS;
+	case conflict_discarded_by_peer:
+		/* for discarded conflicting writes of multiple primaries,
+		 * there is no need to keep anything in the tl, potential
+		 * node crashes are covered by the activity log. */
+		if (what == conflict_discarded_by_peer)
+			dev_alert(DEV, "Got DiscardAck packet %llus +%u!"
+			      " DRBD is not a random data generator!\n",
+			      (unsigned long long)req->sector, req->size);
+		req->rq_state |= RQ_NET_DONE;
+		/* fall through */
+	case write_acked_by_peer:
+		/* protocol C; successfully written on peer.
+		 * Nothing to do here.
+		 * We want to keep the tl in place for all protocols, to cater
+		 * for volatile write-back caches on lower level devices.
+		 *
+		 * A barrier request is expected to have forced all prior
+		 * requests onto stable storage, so completion of a barrier
+		 * request could set NET_DONE right here, and not wait for the
+		 * P_BARRIER_ACK, but that is an unnecessary optimization. */
+
+		/* this makes it effectively the same as for: */
+	case recv_acked_by_peer:
+		/* protocol B; pretends to be successfully written on peer.
+		 * see also notes above in handed_over_to_network about
+		 * protocol != C */
+		req->rq_state |= RQ_NET_OK;
+		D_ASSERT(req->rq_state & RQ_NET_PENDING);
+		dec_ap_pending(mdev);
+		req->rq_state &= ~RQ_NET_PENDING;
+		_req_may_be_done(req, m);
+		break;
+
+	case neg_acked:
+		/* assert something? */
+		if (req->rq_state & RQ_NET_PENDING)
+			dec_ap_pending(mdev);
+		req->rq_state &= ~(RQ_NET_OK|RQ_NET_PENDING);
+
+		req->rq_state |= RQ_NET_DONE;
+		_req_may_be_done(req, m);
+		/* else: done by handed_over_to_network */
+		break;
+
+	case barrier_acked:
+		if (req->rq_state & RQ_NET_PENDING) {
+			/* barrier came in before all requests have been acked.
+			 * this is bad, because if the connection is lost now,
+			 * we won't be able to clean them up... */
+			dev_err(DEV, "FIXME (barrier_acked but pending)\n");
+			trace_drbd_req(req, nothing, "FIXME (barrier_acked but pending)");
+			list_move(&req->tl_requests, &mdev->out_of_sequence_requests);
+		}
+		D_ASSERT(req->rq_state & RQ_NET_SENT);
+		req->rq_state |= RQ_NET_DONE;
+		_req_may_be_done(req, m);
+		break;
+
+	case data_received:
+		D_ASSERT(req->rq_state & RQ_NET_PENDING);
+		dec_ap_pending(mdev);
+		req->rq_state &= ~RQ_NET_PENDING;
+		req->rq_state |= (RQ_NET_OK|RQ_NET_DONE);
+		_req_may_be_done(req, m);
+		break;
+	};
+}
+
+/* we may do a local read if:
+ * - we are consistent (of course),
+ * - or we are generally inconsistent,
+ *   BUT we are still/already IN SYNC for this area.
+ *   since size may be bigger than BM_BLOCK_SIZE,
+ *   we may need to check several bits.
+ */
+static int drbd_may_do_local_read(struct drbd_conf *mdev, sector_t sector, int size)
+{
+	unsigned long sbnr, ebnr;
+	sector_t esector, nr_sectors;
+
+	if (mdev->state.disk == D_UP_TO_DATE)
+		return 1;
+	if (mdev->state.disk >= D_OUTDATED)
+		return 0;
+	if (mdev->state.disk <  D_INCONSISTENT)
+		return 0;
+	/* state.disk == D_INCONSISTENT   We will have a look at the BitMap */
+	nr_sectors = drbd_get_capacity(mdev->this_bdev);
+	esector = sector + (size >> 9) - 1;
+
+	D_ASSERT(sector  < nr_sectors);
+	D_ASSERT(esector < nr_sectors);
+
+	sbnr = BM_SECT_TO_BIT(sector);
+	ebnr = BM_SECT_TO_BIT(esector);
+
+	return 0 == drbd_bm_count_bits(mdev, sbnr, ebnr);
+}
+
+static int drbd_make_request_common(struct drbd_conf *mdev, struct bio *bio)
+{
+	const int rw = bio_rw(bio);
+	const int size = bio->bi_size;
+	const sector_t sector = bio->bi_sector;
+	struct drbd_tl_epoch *b = NULL;
+	struct drbd_request *req;
+	int local, remote;
+	int err = -EIO;
+
+	/* allocate outside of all locks; */
+	req = drbd_req_new(mdev, bio);
+	if (!req) {
+		dec_ap_bio(mdev);
+		/* only pass the error to the upper layers.
+		 * if user cannot handle io errors, that's not our business. */
+		dev_err(DEV, "could not kmalloc() req\n");
+		bio_endio(bio, -ENOMEM);
+		return 0;
+	}
+
+	trace_drbd_bio(mdev, "Rq", bio, 0, req);
+
+	local = get_ldev(mdev);
+	if (!local) {
+		bio_put(req->private_bio); /* or we get a bio leak */
+		req->private_bio = NULL;
+	}
+	if (rw == WRITE) {
+		remote = 1;
+	} else {
+		/* READ || READA */
+		if (local) {
+			if (!drbd_may_do_local_read(mdev, sector, size)) {
+				/* we could kick the syncer to
+				 * sync this extent asap, wait for
+				 * it, then continue locally.
+				 * Or just issue the request remotely.
+				 */
+				local = 0;
+				bio_put(req->private_bio);
+				req->private_bio = NULL;
+				put_ldev(mdev);
+			}
+		}
+		remote = !local && mdev->state.pdsk >= D_UP_TO_DATE;
+	}
+
+	/* If we have a disk, but a READA request is mapped to remote,
+	 * we are R_PRIMARY, D_INCONSISTENT, SyncTarget.
+	 * Just fail that READA request right here.
+	 *
+	 * THINK: maybe fail all READA when not local?
+	 *        or make this configurable...
+	 *        if network is slow, READA won't do any good.
+	 */
+	if (rw == READA && mdev->state.disk >= D_INCONSISTENT && !local) {
+		err = -EWOULDBLOCK;
+		goto fail_and_free_req;
+	}
+
+	/* For WRITES going to the local disk, grab a reference on the target
+	 * extent.  This waits for any resync activity in the corresponding
+	 * resync extent to finish, and, if necessary, pulls in the target
+	 * extent into the activity log, which involves further disk io because
+	 * of transactional on-disk meta data updates. */
+	if (rw == WRITE && local)
+		drbd_al_begin_io(mdev, sector);
+
+	remote = remote && (mdev->state.pdsk == D_UP_TO_DATE ||
+			    (mdev->state.pdsk == D_INCONSISTENT &&
+			     mdev->state.conn >= C_CONNECTED));
+
+	if (!(local || remote)) {
+		dev_err(DEV, "IO ERROR: neither local nor remote disk\n");
+		goto fail_free_complete;
+	}
+
+	/* For WRITE request, we have to make sure that we have an
+	 * unused_spare_tle, in case we need to start a new epoch.
+	 * I try to be smart and avoid to pre-allocate always "just in case",
+	 * but there is a race between testing the bit and pointer outside the
+	 * spinlock, and grabbing the spinlock.
+	 * if we lost that race, we retry.  */
+	if (rw == WRITE && remote &&
+	    mdev->unused_spare_tle == NULL &&
+	    test_bit(CREATE_BARRIER, &mdev->flags)) {
+allocate_barrier:
+		b = kmalloc(sizeof(struct drbd_tl_epoch), GFP_NOIO);
+		if (!b) {
+			dev_err(DEV, "Failed to alloc barrier.\n");
+			err = -ENOMEM;
+			goto fail_free_complete;
+		}
+	}
+
+	/* GOOD, everything prepared, grab the spin_lock */
+	spin_lock_irq(&mdev->req_lock);
+
+	if (remote) {
+		remote = (mdev->state.pdsk == D_UP_TO_DATE ||
+			    (mdev->state.pdsk == D_INCONSISTENT &&
+			     mdev->state.conn >= C_CONNECTED));
+		if (!remote)
+			dev_warn(DEV, "lost connection while grabbing the req_lock!\n");
+		if (!(local || remote)) {
+			dev_err(DEV, "IO ERROR: neither local nor remote disk\n");
+			spin_unlock_irq(&mdev->req_lock);
+			goto fail_free_complete;
+		}
+	}
+
+	if (b && mdev->unused_spare_tle == NULL) {
+		mdev->unused_spare_tle = b;
+		b = NULL;
+	}
+	if (rw == WRITE && remote &&
+	    mdev->unused_spare_tle == NULL &&
+	    test_bit(CREATE_BARRIER, &mdev->flags)) {
+		/* someone closed the current epoch
+		 * while we were grabbing the spinlock */
+		spin_unlock_irq(&mdev->req_lock);
+		goto allocate_barrier;
+	}
+
+
+	/* Update disk stats */
+	_drbd_start_io_acct(mdev, req, bio);
+
+	/* _maybe_start_new_epoch(mdev);
+	 * If we need to generate a write barrier packet, we have to add the
+	 * new epoch (barrier) object, and queue the barrier packet for sending,
+	 * and queue the req's data after it _within the same lock_, otherwise
+	 * we have race conditions were the reorder domains could be mixed up.
+	 *
+	 * Even read requests may start a new epoch and queue the corresponding
+	 * barrier packet.  To get the write ordering right, we only have to
+	 * make sure that, if this is a write request and it triggered a
+	 * barrier packet, this request is queued within the same spinlock. */
+	if (remote && mdev->unused_spare_tle &&
+	    test_and_clear_bit(CREATE_BARRIER, &mdev->flags)) {
+		_tl_add_barrier(mdev, mdev->unused_spare_tle);
+		mdev->unused_spare_tle = NULL;
+	} else {
+		D_ASSERT(!(remote && rw == WRITE &&
+			   test_bit(CREATE_BARRIER, &mdev->flags)));
+	}
+
+	/* NOTE
+	 * Actually, 'local' may be wrong here already, since we may have failed
+	 * to write to the meta data, and may become wrong anytime because of
+	 * local io-error for some other request, which would lead to us
+	 * "detaching" the local disk.
+	 *
+	 * 'remote' may become wrong any time because the network could fail.
+	 *
+	 * This is a harmless race condition, though, since it is handled
+	 * correctly at the appropriate places; so it just defers the failure
+	 * of the respective operation.
+	 */
+
+	/* mark them early for readability.
+	 * this just sets some state flags. */
+	if (remote)
+		_req_mod(req, to_be_send);
+	if (local)
+		_req_mod(req, to_be_submitted);
+
+	/* check this request on the collision detection hash tables.
+	 * if we have a conflict, just complete it here.
+	 * THINK do we want to check reads, too? (I don't think so...) */
+	if (rw == WRITE && _req_conflicts(req)) {
+		/* this is a conflicting request.
+		 * even though it may have been only _partially_
+		 * overlapping with one of the currently pending requests,
+		 * without even submitting or sending it, we will
+		 * pretend that it was successfully served right now.
+		 */
+		if (local) {
+			bio_put(req->private_bio);
+			req->private_bio = NULL;
+			drbd_al_complete_io(mdev, req->sector);
+			put_ldev(mdev);
+			local = 0;
+		}
+		if (remote)
+			dec_ap_pending(mdev);
+		_drbd_end_io_acct(mdev, req);
+		/* THINK: do we want to fail it (-EIO), or pretend success? */
+		bio_endio(req->master_bio, 0);
+		req->master_bio = NULL;
+		dec_ap_bio(mdev);
+		drbd_req_free(req);
+		remote = 0;
+	}
+
+	/* NOTE remote first: to get the concurrent write detection right,
+	 * we must register the request before start of local IO.  */
+	if (remote) {
+		/* either WRITE and C_CONNECTED,
+		 * or READ, and no local disk,
+		 * or READ, but not in sync.
+		 */
+		_req_mod(req, (rw == WRITE)
+				? queue_for_net_write
+				: queue_for_net_read);
+	}
+	spin_unlock_irq(&mdev->req_lock);
+	kfree(b); /* if someone else has beaten us to it... */
+
+	if (local) {
+		req->private_bio->bi_bdev = mdev->ldev->backing_bdev;
+
+		trace_drbd_bio(mdev, "Pri", req->private_bio, 0, NULL);
+
+		if (FAULT_ACTIVE(mdev, rw == WRITE ? DRBD_FAULT_DT_WR
+				     : rw == READ  ? DRBD_FAULT_DT_RD
+				     :               DRBD_FAULT_DT_RA))
+			bio_endio(req->private_bio, -EIO);
+		else
+			generic_make_request(req->private_bio);
+	}
+
+	/* we need to plug ALWAYS since we possibly need to kick lo_dev.
+	 * we plug after submit, so we won't miss an unplug event */
+	drbd_plug_device(mdev);
+
+	return 0;
+
+fail_free_complete:
+	if (rw == WRITE && local)
+		drbd_al_complete_io(mdev, sector);
+fail_and_free_req:
+	if (local) {
+		bio_put(req->private_bio);
+		req->private_bio = NULL;
+		put_ldev(mdev);
+	}
+	bio_endio(bio, err);
+	drbd_req_free(req);
+	dec_ap_bio(mdev);
+	kfree(b);
+
+	return 0;
+}
+
+/* helper function for drbd_make_request
+ * if we can determine just by the mdev (state) that this request will fail,
+ * return 1
+ * otherwise return 0
+ */
+static int drbd_fail_request_early(struct drbd_conf *mdev, int is_write)
+{
+	/* Unconfigured */
+	if (mdev->state.conn == C_DISCONNECTING &&
+	    mdev->state.disk == D_DISKLESS)
+		return 1;
+
+	if (mdev->state.role != R_PRIMARY &&
+		(!allow_oos || is_write)) {
+		if (__ratelimit(&drbd_ratelimit_state)) {
+			dev_err(DEV, "Process %s[%u] tried to %s; "
+			    "since we are not in Primary state, "
+			    "we cannot allow this\n",
+			    current->comm, current->pid,
+			    is_write ? "WRITE" : "READ");
+		}
+		return 1;
+	}
+
+	/*
+	 * Paranoia: we might have been primary, but sync target, or
+	 * even diskless, then lost the connection.
+	 * This should have been handled (panic? suspend?) somewhere
+	 * else. But maybe it was not, so check again here.
+	 * Caution: as long as we do not have a read/write lock on mdev,
+	 * to serialize state changes, this is racy, since we may lose
+	 * the connection *after* we test for the cstate.
+	 */
+	if (mdev->state.disk < D_UP_TO_DATE && mdev->state.pdsk < D_UP_TO_DATE) {
+		if (__ratelimit(&drbd_ratelimit_state))
+			dev_err(DEV, "Sorry, I have no access to good data anymore.\n");
+		return 1;
+	}
+
+	return 0;
+}
+
+int drbd_make_request_26(struct request_queue *q, struct bio *bio)
+{
+	unsigned int s_enr, e_enr;
+	struct drbd_conf *mdev = (struct drbd_conf *) q->queuedata;
+
+	if (drbd_fail_request_early(mdev, bio_data_dir(bio) & WRITE)) {
+		bio_endio(bio, -EPERM);
+		return 0;
+	}
+
+	/* Reject barrier requests if we know the underlying device does
+	 * not support them.
+	 * XXX: Need to get this info from peer as well some how so we
+	 * XXX: reject if EITHER side/data/metadata area does not support them.
+	 *
+	 * because of those XXX, this is not yet enabled,
+	 * i.e. in drbd_init_set_defaults we set the NO_BARRIER_SUPP bit.
+	 */
+	if (unlikely(bio_rw_flagged(bio, BIO_RW_BARRIER) && test_bit(NO_BARRIER_SUPP, &mdev->flags))) {
+		/* dev_warn(DEV, "Rejecting barrier request as underlying device does not support\n"); */
+		bio_endio(bio, -EOPNOTSUPP);
+		return 0;
+	}
+
+	/*
+	 * what we "blindly" assume:
+	 */
+	D_ASSERT(bio->bi_size > 0);
+	D_ASSERT((bio->bi_size & 0x1ff) == 0);
+	D_ASSERT(bio->bi_idx == 0);
+
+	/* to make some things easier, force alignment of requests within the
+	 * granularity of our hash tables */
+	s_enr = bio->bi_sector >> HT_SHIFT;
+	e_enr = (bio->bi_sector+(bio->bi_size>>9)-1) >> HT_SHIFT;
+
+	if (likely(s_enr == e_enr)) {
+		inc_ap_bio(mdev, 1);
+		return drbd_make_request_common(mdev, bio);
+	}
+
+	/* can this bio be split generically?
+	 * Maybe add our own split-arbitrary-bios function. */
+	if (bio->bi_vcnt != 1 || bio->bi_idx != 0 || bio->bi_size > DRBD_MAX_SEGMENT_SIZE) {
+		/* rather error out here than BUG in bio_split */
+		dev_err(DEV, "bio would need to, but cannot, be split: "
+		    "(vcnt=%u,idx=%u,size=%u,sector=%llu)\n",
+		    bio->bi_vcnt, bio->bi_idx, bio->bi_size,
+		    (unsigned long long)bio->bi_sector);
+		bio_endio(bio, -EINVAL);
+	} else {
+		/* This bio crosses some boundary, so we have to split it. */
+		struct bio_pair *bp;
+		/* works for the "do not cross hash slot boundaries" case
+		 * e.g. sector 262269, size 4096
+		 * s_enr = 262269 >> 6 = 4097
+		 * e_enr = (262269+8-1) >> 6 = 4098
+		 * HT_SHIFT = 6
+		 * sps = 64, mask = 63
+		 * first_sectors = 64 - (262269 & 63) = 3
+		 */
+		const sector_t sect = bio->bi_sector;
+		const int sps = 1 << HT_SHIFT; /* sectors per slot */
+		const int mask = sps - 1;
+		const sector_t first_sectors = sps - (sect & mask);
+		bp = bio_split(bio,
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,28)
+				bio_split_pool,
+#endif
+				first_sectors);
+
+		/* we need to get a "reference count" (ap_bio_cnt)
+		 * to avoid races with the disconnect/reconnect/suspend code.
+		 * In case we need to split the bio here, we need to get two references
+		 * atomically, otherwise we might deadlock when trying to submit the
+		 * second one! */
+		inc_ap_bio(mdev, 2);
+
+		D_ASSERT(e_enr == s_enr + 1);
+
+		drbd_make_request_common(mdev, &bp->bio1);
+		drbd_make_request_common(mdev, &bp->bio2);
+		bio_pair_release(bp);
+	}
+	return 0;
+}
+
+/* This is called by bio_add_page().  With this function we reduce
+ * the number of BIOs that span over multiple DRBD_MAX_SEGMENT_SIZEs
+ * units (was AL_EXTENTs).
+ *
+ * we do the calculation within the lower 32bit of the byte offsets,
+ * since we don't care for actual offset, but only check whether it
+ * would cross "activity log extent" boundaries.
+ *
+ * As long as the BIO is empty we have to allow at least one bvec,
+ * regardless of size and offset.  so the resulting bio may still
+ * cross extent boundaries.  those are dealt with (bio_split) in
+ * drbd_make_request_26.
+ */
+int drbd_merge_bvec(struct request_queue *q, struct bvec_merge_data *bvm, struct bio_vec *bvec)
+{
+	struct drbd_conf *mdev = (struct drbd_conf *) q->queuedata;
+	unsigned int bio_offset =
+		(unsigned int)bvm->bi_sector << 9; /* 32 bit */
+	unsigned int bio_size = bvm->bi_size;
+	int limit, backing_limit;
+
+	limit = DRBD_MAX_SEGMENT_SIZE
+	      - ((bio_offset & (DRBD_MAX_SEGMENT_SIZE-1)) + bio_size);
+	if (limit < 0)
+		limit = 0;
+	if (bio_size == 0) {
+		if (limit <= bvec->bv_len)
+			limit = bvec->bv_len;
+	} else if (limit && get_ldev(mdev)) {
+		struct request_queue * const b =
+			mdev->ldev->backing_bdev->bd_disk->queue;
+		if (b->merge_bvec_fn && mdev->ldev->dc.use_bmbv) {
+			backing_limit = b->merge_bvec_fn(b, bvm, bvec);
+			limit = min(limit, backing_limit);
+		}
+		put_ldev(mdev);
+	}
+	return limit;
+}
diff --git a/drivers/block/drbd/drbd_req.h b/drivers/block/drbd/drbd_req.h
new file mode 100644
index 00000000000..d37ab57f120
--- /dev/null
+++ b/drivers/block/drbd/drbd_req.h
@@ -0,0 +1,327 @@
+/*
+   drbd_req.h
+
+   This file is part of DRBD by Philipp Reisner and Lars Ellenberg.
+
+   Copyright (C) 2006-2008, LINBIT Information Technologies GmbH.
+   Copyright (C) 2006-2008, Lars Ellenberg <lars.ellenberg@linbit.com>.
+   Copyright (C) 2006-2008, Philipp Reisner <philipp.reisner@linbit.com>.
+
+   DRBD is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 2, or (at your option)
+   any later version.
+
+   DRBD is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with drbd; see the file COPYING.  If not, write to
+   the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#ifndef _DRBD_REQ_H
+#define _DRBD_REQ_H
+
+#include <linux/autoconf.h>
+#include <linux/module.h>
+
+#include <linux/slab.h>
+#include <linux/drbd.h>
+#include "drbd_int.h"
+#include "drbd_wrappers.h"
+
+/* The request callbacks will be called in irq context by the IDE drivers,
+   and in Softirqs/Tasklets/BH context by the SCSI drivers,
+   and by the receiver and worker in kernel-thread context.
+   Try to get the locking right :) */
+
+/*
+ * Objects of type struct drbd_request do only exist on a R_PRIMARY node, and are
+ * associated with IO requests originating from the block layer above us.
+ *
+ * There are quite a few things that may happen to a drbd request
+ * during its lifetime.
+ *
+ *  It will be created.
+ *  It will be marked with the intention to be
+ *    submitted to local disk and/or
+ *    send via the network.
+ *
+ *  It has to be placed on the transfer log and other housekeeping lists,
+ *  In case we have a network connection.
+ *
+ *  It may be identified as a concurrent (write) request
+ *    and be handled accordingly.
+ *
+ *  It may me handed over to the local disk subsystem.
+ *  It may be completed by the local disk subsystem,
+ *    either sucessfully or with io-error.
+ *  In case it is a READ request, and it failed locally,
+ *    it may be retried remotely.
+ *
+ *  It may be queued for sending.
+ *  It may be handed over to the network stack,
+ *    which may fail.
+ *  It may be acknowledged by the "peer" according to the wire_protocol in use.
+ *    this may be a negative ack.
+ *  It may receive a faked ack when the network connection is lost and the
+ *  transfer log is cleaned up.
+ *  Sending may be canceled due to network connection loss.
+ *  When it finally has outlived its time,
+ *    corresponding dirty bits in the resync-bitmap may be cleared or set,
+ *    it will be destroyed,
+ *    and completion will be signalled to the originator,
+ *      with or without "success".
+ */
+
+enum drbd_req_event {
+	created,
+	to_be_send,
+	to_be_submitted,
+
+	/* XXX yes, now I am inconsistent...
+	 * these two are not "events" but "actions"
+	 * oh, well... */
+	queue_for_net_write,
+	queue_for_net_read,
+
+	send_canceled,
+	send_failed,
+	handed_over_to_network,
+	connection_lost_while_pending,
+	recv_acked_by_peer,
+	write_acked_by_peer,
+	write_acked_by_peer_and_sis, /* and set_in_sync */
+	conflict_discarded_by_peer,
+	neg_acked,
+	barrier_acked, /* in protocol A and B */
+	data_received, /* (remote read) */
+
+	read_completed_with_error,
+	read_ahead_completed_with_error,
+	write_completed_with_error,
+	completed_ok,
+	nothing, /* for tracing only */
+};
+
+/* encoding of request states for now.  we don't actually need that many bits.
+ * we don't need to do atomic bit operations either, since most of the time we
+ * need to look at the connection state and/or manipulate some lists at the
+ * same time, so we should hold the request lock anyways.
+ */
+enum drbd_req_state_bits {
+	/* 210
+	 * 000: no local possible
+	 * 001: to be submitted
+	 *    UNUSED, we could map: 011: submitted, completion still pending
+	 * 110: completed ok
+	 * 010: completed with error
+	 */
+	__RQ_LOCAL_PENDING,
+	__RQ_LOCAL_COMPLETED,
+	__RQ_LOCAL_OK,
+
+	/* 76543
+	 * 00000: no network possible
+	 * 00001: to be send
+	 * 00011: to be send, on worker queue
+	 * 00101: sent, expecting recv_ack (B) or write_ack (C)
+	 * 11101: sent,
+	 *        recv_ack (B) or implicit "ack" (A),
+	 *        still waiting for the barrier ack.
+	 *        master_bio may already be completed and invalidated.
+	 * 11100: write_acked (C),
+	 *        data_received (for remote read, any protocol)
+	 *        or finally the barrier ack has arrived (B,A)...
+	 *        request can be freed
+	 * 01100: neg-acked (write, protocol C)
+	 *        or neg-d-acked (read, any protocol)
+	 *        or killed from the transfer log
+	 *        during cleanup after connection loss
+	 *        request can be freed
+	 * 01000: canceled or send failed...
+	 *        request can be freed
+	 */
+
+	/* if "SENT" is not set, yet, this can still fail or be canceled.
+	 * if "SENT" is set already, we still wait for an Ack packet.
+	 * when cleared, the master_bio may be completed.
+	 * in (B,A) the request object may still linger on the transaction log
+	 * until the corresponding barrier ack comes in */
+	__RQ_NET_PENDING,
+
+	/* If it is QUEUED, and it is a WRITE, it is also registered in the
+	 * transfer log. Currently we need this flag to avoid conflicts between
+	 * worker canceling the request and tl_clear_barrier killing it from
+	 * transfer log.  We should restructure the code so this conflict does
+	 * no longer occur. */
+	__RQ_NET_QUEUED,
+
+	/* well, actually only "handed over to the network stack".
+	 *
+	 * TODO can potentially be dropped because of the similar meaning
+	 * of RQ_NET_SENT and ~RQ_NET_QUEUED.
+	 * however it is not exactly the same. before we drop it
+	 * we must ensure that we can tell a request with network part
+	 * from a request without, regardless of what happens to it. */
+	__RQ_NET_SENT,
+
+	/* when set, the request may be freed (if RQ_NET_QUEUED is clear).
+	 * basically this means the corresponding P_BARRIER_ACK was received */
+	__RQ_NET_DONE,
+
+	/* whether or not we know (C) or pretend (B,A) that the write
+	 * was successfully written on the peer.
+	 */
+	__RQ_NET_OK,
+
+	/* peer called drbd_set_in_sync() for this write */
+	__RQ_NET_SIS,
+
+	/* keep this last, its for the RQ_NET_MASK */
+	__RQ_NET_MAX,
+};
+
+#define RQ_LOCAL_PENDING   (1UL << __RQ_LOCAL_PENDING)
+#define RQ_LOCAL_COMPLETED (1UL << __RQ_LOCAL_COMPLETED)
+#define RQ_LOCAL_OK        (1UL << __RQ_LOCAL_OK)
+
+#define RQ_LOCAL_MASK      ((RQ_LOCAL_OK << 1)-1) /* 0x07 */
+
+#define RQ_NET_PENDING     (1UL << __RQ_NET_PENDING)
+#define RQ_NET_QUEUED      (1UL << __RQ_NET_QUEUED)
+#define RQ_NET_SENT        (1UL << __RQ_NET_SENT)
+#define RQ_NET_DONE        (1UL << __RQ_NET_DONE)
+#define RQ_NET_OK          (1UL << __RQ_NET_OK)
+#define RQ_NET_SIS         (1UL << __RQ_NET_SIS)
+
+/* 0x1f8 */
+#define RQ_NET_MASK        (((1UL << __RQ_NET_MAX)-1) & ~RQ_LOCAL_MASK)
+
+/* epoch entries */
+static inline
+struct hlist_head *ee_hash_slot(struct drbd_conf *mdev, sector_t sector)
+{
+	BUG_ON(mdev->ee_hash_s == 0);
+	return mdev->ee_hash +
+		((unsigned int)(sector>>HT_SHIFT) % mdev->ee_hash_s);
+}
+
+/* transfer log (drbd_request objects) */
+static inline
+struct hlist_head *tl_hash_slot(struct drbd_conf *mdev, sector_t sector)
+{
+	BUG_ON(mdev->tl_hash_s == 0);
+	return mdev->tl_hash +
+		((unsigned int)(sector>>HT_SHIFT) % mdev->tl_hash_s);
+}
+
+/* application reads (drbd_request objects) */
+static struct hlist_head *ar_hash_slot(struct drbd_conf *mdev, sector_t sector)
+{
+	return mdev->app_reads_hash
+		+ ((unsigned int)(sector) % APP_R_HSIZE);
+}
+
+/* when we receive the answer for a read request,
+ * verify that we actually know about it */
+static inline struct drbd_request *_ar_id_to_req(struct drbd_conf *mdev,
+	u64 id, sector_t sector)
+{
+	struct hlist_head *slot = ar_hash_slot(mdev, sector);
+	struct hlist_node *n;
+	struct drbd_request *req;
+
+	hlist_for_each_entry(req, n, slot, colision) {
+		if ((unsigned long)req == (unsigned long)id) {
+			D_ASSERT(req->sector == sector);
+			return req;
+		}
+	}
+	return NULL;
+}
+
+static inline struct drbd_request *drbd_req_new(struct drbd_conf *mdev,
+	struct bio *bio_src)
+{
+	struct bio *bio;
+	struct drbd_request *req =
+		mempool_alloc(drbd_request_mempool, GFP_NOIO);
+	if (likely(req)) {
+		bio = bio_clone(bio_src, GFP_NOIO); /* XXX cannot fail?? */
+
+		req->rq_state    = 0;
+		req->mdev        = mdev;
+		req->master_bio  = bio_src;
+		req->private_bio = bio;
+		req->epoch       = 0;
+		req->sector      = bio->bi_sector;
+		req->size        = bio->bi_size;
+		req->start_time  = jiffies;
+		INIT_HLIST_NODE(&req->colision);
+		INIT_LIST_HEAD(&req->tl_requests);
+		INIT_LIST_HEAD(&req->w.list);
+
+		bio->bi_private  = req;
+		bio->bi_end_io   = drbd_endio_pri;
+		bio->bi_next     = NULL;
+	}
+	return req;
+}
+
+static inline void drbd_req_free(struct drbd_request *req)
+{
+	mempool_free(req, drbd_request_mempool);
+}
+
+static inline int overlaps(sector_t s1, int l1, sector_t s2, int l2)
+{
+	return !((s1 + (l1>>9) <= s2) || (s1 >= s2 + (l2>>9)));
+}
+
+/* Short lived temporary struct on the stack.
+ * We could squirrel the error to be returned into
+ * bio->bi_size, or similar. But that would be too ugly. */
+struct bio_and_error {
+	struct bio *bio;
+	int error;
+};
+
+extern void _req_may_be_done(struct drbd_request *req,
+		struct bio_and_error *m);
+extern void __req_mod(struct drbd_request *req, enum drbd_req_event what,
+		struct bio_and_error *m);
+extern void complete_master_bio(struct drbd_conf *mdev,
+		struct bio_and_error *m);
+
+/* use this if you don't want to deal with calling complete_master_bio()
+ * outside the spinlock, e.g. when walking some list on cleanup. */
+static inline void _req_mod(struct drbd_request *req, enum drbd_req_event what)
+{
+	struct drbd_conf *mdev = req->mdev;
+	struct bio_and_error m;
+
+	/* __req_mod possibly frees req, do not touch req after that! */
+	__req_mod(req, what, &m);
+	if (m.bio)
+		complete_master_bio(mdev, &m);
+}
+
+/* completion of master bio is outside of spinlock.
+ * If you need it irqsave, do it your self! */
+static inline void req_mod(struct drbd_request *req,
+		enum drbd_req_event what)
+{
+	struct drbd_conf *mdev = req->mdev;
+	struct bio_and_error m;
+	spin_lock_irq(&mdev->req_lock);
+	__req_mod(req, what, &m);
+	spin_unlock_irq(&mdev->req_lock);
+
+	if (m.bio)
+		complete_master_bio(mdev, &m);
+}
+#endif
diff --git a/drivers/block/drbd/drbd_strings.c b/drivers/block/drbd/drbd_strings.c
new file mode 100644
index 00000000000..76863e3f05b
--- /dev/null
+++ b/drivers/block/drbd/drbd_strings.c
@@ -0,0 +1,113 @@
+/*
+  drbd.h
+
+  This file is part of DRBD by Philipp Reisner and Lars Ellenberg.
+
+  Copyright (C) 2003-2008, LINBIT Information Technologies GmbH.
+  Copyright (C) 2003-2008, Philipp Reisner <philipp.reisner@linbit.com>.
+  Copyright (C) 2003-2008, Lars Ellenberg <lars.ellenberg@linbit.com>.
+
+  drbd is free software; you can redistribute it and/or modify
+  it under the terms of the GNU General Public License as published by
+  the Free Software Foundation; either version 2, or (at your option)
+  any later version.
+
+  drbd is distributed in the hope that it will be useful,
+  but WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+  GNU General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with drbd; see the file COPYING.  If not, write to
+  the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
+
+*/
+
+#include <linux/drbd.h>
+
+static const char *drbd_conn_s_names[] = {
+	[C_STANDALONE]       = "StandAlone",
+	[C_DISCONNECTING]    = "Disconnecting",
+	[C_UNCONNECTED]      = "Unconnected",
+	[C_TIMEOUT]          = "Timeout",
+	[C_BROKEN_PIPE]      = "BrokenPipe",
+	[C_NETWORK_FAILURE]  = "NetworkFailure",
+	[C_PROTOCOL_ERROR]   = "ProtocolError",
+	[C_WF_CONNECTION]    = "WFConnection",
+	[C_WF_REPORT_PARAMS] = "WFReportParams",
+	[C_TEAR_DOWN]        = "TearDown",
+	[C_CONNECTED]        = "Connected",
+	[C_STARTING_SYNC_S]  = "StartingSyncS",
+	[C_STARTING_SYNC_T]  = "StartingSyncT",
+	[C_WF_BITMAP_S]      = "WFBitMapS",
+	[C_WF_BITMAP_T]      = "WFBitMapT",
+	[C_WF_SYNC_UUID]     = "WFSyncUUID",
+	[C_SYNC_SOURCE]      = "SyncSource",
+	[C_SYNC_TARGET]      = "SyncTarget",
+	[C_PAUSED_SYNC_S]    = "PausedSyncS",
+	[C_PAUSED_SYNC_T]    = "PausedSyncT",
+	[C_VERIFY_S]         = "VerifyS",
+	[C_VERIFY_T]         = "VerifyT",
+};
+
+static const char *drbd_role_s_names[] = {
+	[R_PRIMARY]   = "Primary",
+	[R_SECONDARY] = "Secondary",
+	[R_UNKNOWN]   = "Unknown"
+};
+
+static const char *drbd_disk_s_names[] = {
+	[D_DISKLESS]     = "Diskless",
+	[D_ATTACHING]    = "Attaching",
+	[D_FAILED]       = "Failed",
+	[D_NEGOTIATING]  = "Negotiating",
+	[D_INCONSISTENT] = "Inconsistent",
+	[D_OUTDATED]     = "Outdated",
+	[D_UNKNOWN]      = "DUnknown",
+	[D_CONSISTENT]   = "Consistent",
+	[D_UP_TO_DATE]   = "UpToDate",
+};
+
+static const char *drbd_state_sw_errors[] = {
+	[-SS_TWO_PRIMARIES] = "Multiple primaries not allowed by config",
+	[-SS_NO_UP_TO_DATE_DISK] = "Refusing to be Primary without at least one UpToDate disk",
+	[-SS_NO_LOCAL_DISK] = "Can not resync without local disk",
+	[-SS_NO_REMOTE_DISK] = "Can not resync without remote disk",
+	[-SS_CONNECTED_OUTDATES] = "Refusing to be Outdated while Connected",
+	[-SS_PRIMARY_NOP] = "Refusing to be Primary while peer is not outdated",
+	[-SS_RESYNC_RUNNING] = "Can not start OV/resync since it is already active",
+	[-SS_ALREADY_STANDALONE] = "Can not disconnect a StandAlone device",
+	[-SS_CW_FAILED_BY_PEER] = "State change was refused by peer node",
+	[-SS_IS_DISKLESS] = "Device is diskless, the requested operation requires a disk",
+	[-SS_DEVICE_IN_USE] = "Device is held open by someone",
+	[-SS_NO_NET_CONFIG] = "Have no net/connection configuration",
+	[-SS_NO_VERIFY_ALG] = "Need a verify algorithm to start online verify",
+	[-SS_NEED_CONNECTION] = "Need a connection to start verify or resync",
+	[-SS_NOT_SUPPORTED] = "Peer does not support protocol",
+	[-SS_LOWER_THAN_OUTDATED] = "Disk state is lower than outdated",
+	[-SS_IN_TRANSIENT_STATE] = "In transient state, retry after next state change",
+	[-SS_CONCURRENT_ST_CHG] = "Concurrent state changes detected and aborted",
+};
+
+const char *drbd_conn_str(enum drbd_conns s)
+{
+	/* enums are unsigned... */
+	return s > C_PAUSED_SYNC_T ? "TOO_LARGE" : drbd_conn_s_names[s];
+}
+
+const char *drbd_role_str(enum drbd_role s)
+{
+	return s > R_SECONDARY   ? "TOO_LARGE" : drbd_role_s_names[s];
+}
+
+const char *drbd_disk_str(enum drbd_disk_state s)
+{
+	return s > D_UP_TO_DATE    ? "TOO_LARGE" : drbd_disk_s_names[s];
+}
+
+const char *drbd_set_st_err_str(enum drbd_state_ret_codes err)
+{
+	return err <= SS_AFTER_LAST_ERROR ? "TOO_SMALL" :
+	       err > SS_TWO_PRIMARIES ? "TOO_LARGE"
+			: drbd_state_sw_errors[-err];
+}
diff --git a/drivers/block/drbd/drbd_tracing.c b/drivers/block/drbd/drbd_tracing.c
new file mode 100644
index 00000000000..d18d4f7b4be
--- /dev/null
+++ b/drivers/block/drbd/drbd_tracing.c
@@ -0,0 +1,752 @@
+/*
+   drbd_tracing.c
+
+   This file is part of DRBD by Philipp Reisner and Lars Ellenberg.
+
+   Copyright (C) 2003-2008, LINBIT Information Technologies GmbH.
+   Copyright (C) 2003-2008, Philipp Reisner <philipp.reisner@linbit.com>.
+   Copyright (C) 2003-2008, Lars Ellenberg <lars.ellenberg@linbit.com>.
+
+   drbd is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 2, or (at your option)
+   any later version.
+
+   drbd is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with drbd; see the file COPYING.  If not, write to
+   the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
+
+ */
+
+#include <linux/module.h>
+#include <linux/drbd.h>
+#include <linux/ctype.h>
+#include "drbd_int.h"
+#include "drbd_tracing.h"
+#include <linux/drbd_tag_magic.h>
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Philipp Reisner, Lars Ellenberg");
+MODULE_DESCRIPTION("DRBD tracepoint probes");
+MODULE_PARM_DESC(trace_mask, "Bitmap of events to trace see drbd_tracing.c");
+MODULE_PARM_DESC(trace_level, "Current tracing level (changeable in /sys)");
+MODULE_PARM_DESC(trace_devs, "Bitmap of devices to trace (changeable in /sys)");
+
+unsigned int trace_mask = 0;  /* Bitmap of events to trace */
+int trace_level;              /* Current trace level */
+int trace_devs;		      /* Bitmap of devices to trace */
+
+module_param(trace_mask, uint, 0444);
+module_param(trace_level, int, 0644);
+module_param(trace_devs, int, 0644);
+
+enum {
+	TRACE_PACKET  = 0x0001,
+	TRACE_RQ      = 0x0002,
+	TRACE_UUID    = 0x0004,
+	TRACE_RESYNC  = 0x0008,
+	TRACE_EE      = 0x0010,
+	TRACE_UNPLUG  = 0x0020,
+	TRACE_NL      = 0x0040,
+	TRACE_AL_EXT  = 0x0080,
+	TRACE_INT_RQ  = 0x0100,
+	TRACE_MD_IO   = 0x0200,
+	TRACE_EPOCH   = 0x0400,
+};
+
+/* Buffer printing support
+ * dbg_print_flags: used for Flags arg to drbd_print_buffer
+ * - DBGPRINT_BUFFADDR; if set, each line starts with the
+ *	 virtual address of the line being output. If clear,
+ *	 each line starts with the offset from the beginning
+ *	 of the buffer. */
+enum dbg_print_flags {
+    DBGPRINT_BUFFADDR = 0x0001,
+};
+
+/* Macro stuff */
+static char *nl_packet_name(int packet_type)
+{
+/* Generate packet type strings */
+#define NL_PACKET(name, number, fields) \
+	[P_ ## name] = # name,
+#define NL_INTEGER Argh!
+#define NL_BIT Argh!
+#define NL_INT64 Argh!
+#define NL_STRING Argh!
+
+	static char *nl_tag_name[P_nl_after_last_packet] = {
+#include "linux/drbd_nl.h"
+	};
+
+	return (packet_type < sizeof(nl_tag_name)/sizeof(nl_tag_name[0])) ?
+	    nl_tag_name[packet_type] : "*Unknown*";
+}
+/* /Macro stuff */
+
+static inline int is_mdev_trace(struct drbd_conf *mdev, unsigned int level)
+{
+	return trace_level >= level && ((1 << mdev_to_minor(mdev)) & trace_devs);
+}
+
+static void probe_drbd_unplug(struct drbd_conf *mdev, char *msg)
+{
+	if (!is_mdev_trace(mdev, TRACE_LVL_ALWAYS))
+		return;
+
+	dev_info(DEV, "%s, ap_bio_count=%d\n", msg, atomic_read(&mdev->ap_bio_cnt));
+}
+
+static void probe_drbd_uuid(struct drbd_conf *mdev, enum drbd_uuid_index index)
+{
+	static char *uuid_str[UI_EXTENDED_SIZE] = {
+		[UI_CURRENT] = "CURRENT",
+		[UI_BITMAP] = "BITMAP",
+		[UI_HISTORY_START] = "HISTORY_START",
+		[UI_HISTORY_END] = "HISTORY_END",
+		[UI_SIZE] = "SIZE",
+		[UI_FLAGS] = "FLAGS",
+	};
+
+	if (!is_mdev_trace(mdev, TRACE_LVL_ALWAYS))
+		return;
+
+	if (index >= UI_EXTENDED_SIZE) {
+		dev_warn(DEV, " uuid_index >= EXTENDED_SIZE\n");
+		return;
+	}
+
+	dev_info(DEV, " uuid[%s] now %016llX\n",
+		 uuid_str[index],
+		 (unsigned long long)mdev->ldev->md.uuid[index]);
+}
+
+static void probe_drbd_md_io(struct drbd_conf *mdev, int rw,
+			     struct drbd_backing_dev *bdev)
+{
+	if (!is_mdev_trace(mdev, TRACE_LVL_ALWAYS))
+		return;
+
+	dev_info(DEV, " %s metadata superblock now\n",
+		 rw == READ ? "Reading" : "Writing");
+}
+
+static void probe_drbd_ee(struct drbd_conf *mdev, struct drbd_epoch_entry *e, char* msg)
+{
+	if (!is_mdev_trace(mdev, TRACE_LVL_ALWAYS))
+		return;
+
+	dev_info(DEV, "EE %s sec=%llus size=%u e=%p\n",
+		 msg, (unsigned long long)e->sector, e->size, e);
+}
+
+static void probe_drbd_epoch(struct drbd_conf *mdev, struct drbd_epoch *epoch,
+			     enum epoch_event ev)
+{
+	static char *epoch_event_str[] = {
+		[EV_PUT] = "put",
+		[EV_GOT_BARRIER_NR] = "got_barrier_nr",
+		[EV_BARRIER_DONE] = "barrier_done",
+		[EV_BECAME_LAST] = "became_last",
+		[EV_TRACE_FLUSH] = "issuing_flush",
+		[EV_TRACE_ADD_BARRIER] = "added_barrier",
+		[EV_TRACE_SETTING_BI] = "just set barrier_in_next_epoch",
+	};
+
+	if (!is_mdev_trace(mdev, TRACE_LVL_ALWAYS))
+		return;
+
+	ev &= ~EV_CLEANUP;
+
+	switch (ev) {
+	case EV_TRACE_ALLOC:
+		dev_info(DEV, "Allocate epoch %p/xxxx { } nr_epochs=%d\n", epoch, mdev->epochs);
+		break;
+	case EV_TRACE_FREE:
+		dev_info(DEV, "Freeing epoch %p/%d { size=%d } nr_epochs=%d\n",
+			 epoch, epoch->barrier_nr, atomic_read(&epoch->epoch_size),
+			 mdev->epochs);
+		break;
+	default:
+		dev_info(DEV, "Update epoch  %p/%d { size=%d active=%d %c%c n%c%c } ev=%s\n",
+			 epoch, epoch->barrier_nr, atomic_read(&epoch->epoch_size),
+			 atomic_read(&epoch->active),
+			 test_bit(DE_HAVE_BARRIER_NUMBER, &epoch->flags) ? 'n' : '-',
+			 test_bit(DE_CONTAINS_A_BARRIER, &epoch->flags) ? 'b' : '-',
+			 test_bit(DE_BARRIER_IN_NEXT_EPOCH_ISSUED, &epoch->flags) ? 'i' : '-',
+			 test_bit(DE_BARRIER_IN_NEXT_EPOCH_DONE, &epoch->flags) ? 'd' : '-',
+			 epoch_event_str[ev]);
+	}
+}
+
+static void probe_drbd_netlink(void *data, int is_req)
+{
+	struct cn_msg *msg = data;
+
+	if (is_req) {
+		struct drbd_nl_cfg_req *nlp = (struct drbd_nl_cfg_req *)msg->data;
+
+		printk(KERN_INFO "drbd%d: "
+			 "Netlink: << %s (%d) - seq: %x, ack: %x, len: %x\n",
+			 nlp->drbd_minor,
+			 nl_packet_name(nlp->packet_type),
+			 nlp->packet_type,
+			 msg->seq, msg->ack, msg->len);
+	} else {
+		struct drbd_nl_cfg_reply *nlp = (struct drbd_nl_cfg_reply *)msg->data;
+
+		printk(KERN_INFO "drbd%d: "
+		       "Netlink: >> %s (%d) - seq: %x, ack: %x, len: %x\n",
+		       nlp->minor,
+		       nlp->packet_type == P_nl_after_last_packet ?
+		       "Empty-Reply" : nl_packet_name(nlp->packet_type),
+		       nlp->packet_type,
+		       msg->seq, msg->ack, msg->len);
+	}
+}
+
+static void probe_drbd_actlog(struct drbd_conf *mdev, sector_t sector, char* msg)
+{
+	unsigned int enr = (sector >> (AL_EXTENT_SHIFT-9));
+
+	if (!is_mdev_trace(mdev, TRACE_LVL_ALWAYS))
+		return;
+
+	dev_info(DEV, "%s (sec=%llus, al_enr=%u, rs_enr=%d)\n",
+		 msg, (unsigned long long) sector, enr,
+		 (int)BM_SECT_TO_EXT(sector));
+}
+
+/**
+ * drbd_print_buffer() - Hexdump arbitrary binary data into a buffer
+ * @prefix:	String is output at the beginning of each line output.
+ * @flags:	Currently only defined flag: DBGPRINT_BUFFADDR; if set, each
+ *		line starts with the virtual address of the line being
+ *		output. If clear, each line starts with the offset from the
+ *		beginning of the buffer.
+ * @size:	Indicates the size of each entry in the buffer. Supported
+ * 		values are sizeof(char), sizeof(short) and sizeof(int)
+ * @buffer:	Start address of buffer
+ * @buffer_va:	Virtual address of start of buffer (normally the same
+ *		as Buffer, but having it separate allows it to hold
+ *		file address for example)
+ * @length:	length of buffer
+ */
+static void drbd_print_buffer(const char *prefix, unsigned int flags, int size,
+			      const void *buffer, const void *buffer_va,
+			      unsigned int length)
+
+#define LINE_SIZE       16
+#define LINE_ENTRIES    (int)(LINE_SIZE/size)
+{
+	const unsigned char *pstart;
+	const unsigned char *pstart_va;
+	const unsigned char *pend;
+	char bytes_str[LINE_SIZE*3+8], ascii_str[LINE_SIZE+8];
+	char *pbytes = bytes_str, *pascii = ascii_str;
+	int  offset = 0;
+	long sizemask;
+	int  field_width;
+	int  index;
+	const unsigned char *pend_str;
+	const unsigned char *p;
+	int count;
+
+	/* verify size parameter */
+	if (size != sizeof(char) &&
+	    size != sizeof(short) &&
+	    size != sizeof(int)) {
+		printk(KERN_DEBUG "drbd_print_buffer: "
+			"ERROR invalid size %d\n", size);
+		return;
+	}
+
+	sizemask = size-1;
+	field_width = size*2;
+
+	/* Adjust start/end to be on appropriate boundary for size */
+	buffer = (const char *)((long)buffer & ~sizemask);
+	pend   = (const unsigned char *)
+		(((long)buffer + length + sizemask) & ~sizemask);
+
+	if (flags & DBGPRINT_BUFFADDR) {
+		/* Move start back to nearest multiple of line size,
+		 * if printing address. This results in nicely formatted output
+		 * with addresses being on line size (16) byte boundaries */
+		pstart = (const unsigned char *)((long)buffer & ~(LINE_SIZE-1));
+	} else {
+		pstart = (const unsigned char *)buffer;
+	}
+
+	/* Set value of start VA to print if addresses asked for */
+	pstart_va = (const unsigned char *)buffer_va
+		 - ((const unsigned char *)buffer-pstart);
+
+	/* Calculate end position to nicely align right hand side */
+	pend_str = pstart + (((pend-pstart) + LINE_SIZE-1) & ~(LINE_SIZE-1));
+
+	/* Init strings */
+	*pbytes = *pascii = '\0';
+
+	/* Start at beginning of first line */
+	p = pstart;
+	count = 0;
+
+	while (p < pend_str) {
+		if (p < (const unsigned char *)buffer || p >= pend) {
+			/* Before start of buffer or after end- print spaces */
+			pbytes += sprintf(pbytes, "%*c ", field_width, ' ');
+			pascii += sprintf(pascii, "%*c", size, ' ');
+			p += size;
+		} else {
+			/* Add hex and ascii to strings */
+			int val;
+			switch (size) {
+			default:
+			case 1:
+				val = *(unsigned char *)p;
+				break;
+			case 2:
+				val = *(unsigned short *)p;
+				break;
+			case 4:
+				val = *(unsigned int *)p;
+				break;
+			}
+
+			pbytes += sprintf(pbytes, "%0*x ", field_width, val);
+
+			for (index = size; index; index--) {
+				*pascii++ = isprint(*p) ? *p : '.';
+				p++;
+			}
+		}
+
+		count++;
+
+		if (count == LINE_ENTRIES || p >= pend_str) {
+			/* Null terminate and print record */
+			*pascii = '\0';
+			printk(KERN_DEBUG "%s%8.8lx: %*s|%*s|\n",
+			       prefix,
+			       (flags & DBGPRINT_BUFFADDR)
+			       ? (long)pstart_va:(long)offset,
+			       LINE_ENTRIES*(field_width+1), bytes_str,
+			       LINE_SIZE, ascii_str);
+
+			/* Move onto next line */
+			pstart_va += (p-pstart);
+			pstart = p;
+			count  = 0;
+			offset += LINE_SIZE;
+
+			/* Re-init strings */
+			pbytes = bytes_str;
+			pascii = ascii_str;
+			*pbytes = *pascii = '\0';
+		}
+	}
+}
+
+static void probe_drbd_resync(struct drbd_conf *mdev, int level, const char *fmt, va_list args)
+{
+	char str[256];
+
+	if (!is_mdev_trace(mdev, level))
+		return;
+
+	if (vsnprintf(str, 256, fmt, args) >= 256)
+		str[255] = 0;
+
+	printk(KERN_INFO "%s %s: %s", dev_driver_string(disk_to_dev(mdev->vdisk)),
+	       dev_name(disk_to_dev(mdev->vdisk)), str);
+}
+
+static void probe_drbd_bio(struct drbd_conf *mdev, const char *pfx, struct bio *bio, int complete,
+			   struct drbd_request *r)
+{
+#if defined(CONFIG_LBDAF) || defined(CONFIG_LBD)
+#define SECTOR_FORMAT "%Lx"
+#else
+#define SECTOR_FORMAT "%lx"
+#endif
+#define SECTOR_SHIFT 9
+
+	unsigned long lowaddr = (unsigned long)(bio->bi_sector << SECTOR_SHIFT);
+	char *faddr = (char *)(lowaddr);
+	char rb[sizeof(void *)*2+6] = { 0, };
+	struct bio_vec *bvec;
+	int segno;
+
+	const int rw = bio->bi_rw;
+	const int biorw      = (rw & (RW_MASK|RWA_MASK));
+	const int biobarrier = (rw & (1<<BIO_RW_BARRIER));
+	const int biosync = (rw & ((1<<BIO_RW_UNPLUG) | (1<<BIO_RW_SYNCIO)));
+
+	if (!is_mdev_trace(mdev, TRACE_LVL_ALWAYS))
+		return;
+
+	if (r)
+		sprintf(rb, "Req:%p ", r);
+
+	dev_info(DEV, "%s %s:%s%s%s Bio:%p %s- %soffset " SECTOR_FORMAT ", size %x\n",
+		 complete ? "<<<" : ">>>",
+		 pfx,
+		 biorw == WRITE ? "Write" : "Read",
+		 biobarrier ? " : B" : "",
+		 biosync ? " : S" : "",
+		 bio,
+		 rb,
+		 complete ? (bio_flagged(bio, BIO_UPTODATE) ? "Success, " : "Failed, ") : "",
+		 bio->bi_sector << SECTOR_SHIFT,
+		 bio->bi_size);
+
+	if (trace_level >= TRACE_LVL_METRICS &&
+	    ((biorw == WRITE) ^ complete)) {
+		printk(KERN_DEBUG "  ind     page   offset   length\n");
+		__bio_for_each_segment(bvec, bio, segno, 0) {
+			printk(KERN_DEBUG "  [%d] %p %8.8x %8.8x\n", segno,
+			       bvec->bv_page, bvec->bv_offset, bvec->bv_len);
+
+			if (trace_level >= TRACE_LVL_ALL) {
+				char *bvec_buf;
+				unsigned long flags;
+
+				bvec_buf = bvec_kmap_irq(bvec, &flags);
+
+				drbd_print_buffer("    ", DBGPRINT_BUFFADDR, 1,
+						  bvec_buf,
+						  faddr,
+						  (bvec->bv_len <= 0x80)
+						  ? bvec->bv_len : 0x80);
+
+				bvec_kunmap_irq(bvec_buf, &flags);
+
+				if (bvec->bv_len > 0x40)
+					printk(KERN_DEBUG "    ....\n");
+
+				faddr += bvec->bv_len;
+			}
+		}
+	}
+}
+
+static void probe_drbd_req(struct drbd_request *req, enum drbd_req_event what, char *msg)
+{
+	static const char *rq_event_names[] = {
+		[created] = "created",
+		[to_be_send] = "to_be_send",
+		[to_be_submitted] = "to_be_submitted",
+		[queue_for_net_write] = "queue_for_net_write",
+		[queue_for_net_read] = "queue_for_net_read",
+		[send_canceled] = "send_canceled",
+		[send_failed] = "send_failed",
+		[handed_over_to_network] = "handed_over_to_network",
+		[connection_lost_while_pending] =
+					"connection_lost_while_pending",
+		[recv_acked_by_peer] = "recv_acked_by_peer",
+		[write_acked_by_peer] = "write_acked_by_peer",
+		[neg_acked] = "neg_acked",
+		[conflict_discarded_by_peer] = "conflict_discarded_by_peer",
+		[barrier_acked] = "barrier_acked",
+		[data_received] = "data_received",
+		[read_completed_with_error] = "read_completed_with_error",
+		[read_ahead_completed_with_error] = "reada_completed_with_error",
+		[write_completed_with_error] = "write_completed_with_error",
+		[completed_ok] = "completed_ok",
+	};
+
+	struct drbd_conf *mdev = req->mdev;
+
+	const int rw = (req->master_bio == NULL ||
+			bio_data_dir(req->master_bio) == WRITE) ?
+		'W' : 'R';
+	const unsigned long s = req->rq_state;
+
+	if (what != nothing) {
+		dev_info(DEV, "__req_mod(%p %c ,%s)\n", req, rw, rq_event_names[what]);
+	} else {
+		dev_info(DEV, "%s %p %c L%c%c%cN%c%c%c%c%c %u (%llus +%u) %s\n",
+			 msg, req, rw,
+			 s & RQ_LOCAL_PENDING ? 'p' : '-',
+			 s & RQ_LOCAL_COMPLETED ? 'c' : '-',
+			 s & RQ_LOCAL_OK ? 'o' : '-',
+			 s & RQ_NET_PENDING ? 'p' : '-',
+			 s & RQ_NET_QUEUED ? 'q' : '-',
+			 s & RQ_NET_SENT ? 's' : '-',
+			 s & RQ_NET_DONE ? 'd' : '-',
+			 s & RQ_NET_OK ? 'o' : '-',
+			 req->epoch,
+			 (unsigned long long)req->sector,
+			 req->size,
+			 drbd_conn_str(mdev->state.conn));
+	}
+}
+
+
+#define drbd_peer_str drbd_role_str
+#define drbd_pdsk_str drbd_disk_str
+
+#define PSM(A)							\
+do {								\
+	if (mask.A) {						\
+		int i = snprintf(p, len, " " #A "( %s )",	\
+				 drbd_##A##_str(val.A));	\
+		if (i >= len)					\
+			return op;				\
+		p += i;						\
+		len -= i;					\
+	}							\
+} while (0)
+
+static char *dump_st(char *p, int len, union drbd_state mask, union drbd_state val)
+{
+	char *op = p;
+	*p = '\0';
+	PSM(role);
+	PSM(peer);
+	PSM(conn);
+	PSM(disk);
+	PSM(pdsk);
+
+	return op;
+}
+
+#define INFOP(fmt, args...) \
+do { \
+	if (trace_level >= TRACE_LVL_ALL) { \
+		dev_info(DEV, "%s:%d: %s [%d] %s %s " fmt , \
+		     file, line, current->comm, current->pid, \
+		     sockname, recv ? "<<<" : ">>>" , \
+		     ## args); \
+	} else { \
+		dev_info(DEV, "%s %s " fmt, sockname, \
+		     recv ? "<<<" : ">>>" , \
+		     ## args); \
+	} \
+} while (0)
+
+static char *_dump_block_id(u64 block_id, char *buff)
+{
+	if (is_syncer_block_id(block_id))
+		strcpy(buff, "SyncerId");
+	else
+		sprintf(buff, "%llx", (unsigned long long)block_id);
+
+	return buff;
+}
+
+static void probe_drbd_packet(struct drbd_conf *mdev, struct socket *sock,
+			      int recv, union p_polymorph *p, char *file, int line)
+{
+	char *sockname = sock == mdev->meta.socket ? "meta" : "data";
+	int cmd = (recv == 2) ? p->header.command : be16_to_cpu(p->header.command);
+	char tmp[300];
+	union drbd_state m, v;
+
+	switch (cmd) {
+	case P_HAND_SHAKE:
+		INFOP("%s (protocol %u-%u)\n", cmdname(cmd),
+			be32_to_cpu(p->handshake.protocol_min),
+			be32_to_cpu(p->handshake.protocol_max));
+		break;
+
+	case P_BITMAP: /* don't report this */
+	case P_COMPRESSED_BITMAP: /* don't report this */
+		break;
+
+	case P_DATA:
+		INFOP("%s (sector %llus, id %s, seq %u, f %x)\n", cmdname(cmd),
+		      (unsigned long long)be64_to_cpu(p->data.sector),
+		      _dump_block_id(p->data.block_id, tmp),
+		      be32_to_cpu(p->data.seq_num),
+		      be32_to_cpu(p->data.dp_flags)
+			);
+		break;
+
+	case P_DATA_REPLY:
+	case P_RS_DATA_REPLY:
+		INFOP("%s (sector %llus, id %s)\n", cmdname(cmd),
+		      (unsigned long long)be64_to_cpu(p->data.sector),
+		      _dump_block_id(p->data.block_id, tmp)
+			);
+		break;
+
+	case P_RECV_ACK:
+	case P_WRITE_ACK:
+	case P_RS_WRITE_ACK:
+	case P_DISCARD_ACK:
+	case P_NEG_ACK:
+	case P_NEG_RS_DREPLY:
+		INFOP("%s (sector %llus, size %u, id %s, seq %u)\n",
+			cmdname(cmd),
+		      (long long)be64_to_cpu(p->block_ack.sector),
+		      be32_to_cpu(p->block_ack.blksize),
+		      _dump_block_id(p->block_ack.block_id, tmp),
+		      be32_to_cpu(p->block_ack.seq_num)
+			);
+		break;
+
+	case P_DATA_REQUEST:
+	case P_RS_DATA_REQUEST:
+		INFOP("%s (sector %llus, size %u, id %s)\n", cmdname(cmd),
+		      (long long)be64_to_cpu(p->block_req.sector),
+		      be32_to_cpu(p->block_req.blksize),
+		      _dump_block_id(p->block_req.block_id, tmp)
+			);
+		break;
+
+	case P_BARRIER:
+	case P_BARRIER_ACK:
+		INFOP("%s (barrier %u)\n", cmdname(cmd), p->barrier.barrier);
+		break;
+
+	case P_SYNC_PARAM:
+	case P_SYNC_PARAM89:
+		INFOP("%s (rate %u, verify-alg \"%.64s\", csums-alg \"%.64s\")\n",
+			cmdname(cmd), be32_to_cpu(p->rs_param_89.rate),
+			p->rs_param_89.verify_alg, p->rs_param_89.csums_alg);
+		break;
+
+	case P_UUIDS:
+		INFOP("%s Curr:%016llX, Bitmap:%016llX, "
+		      "HisSt:%016llX, HisEnd:%016llX\n",
+		      cmdname(cmd),
+		      (unsigned long long)be64_to_cpu(p->uuids.uuid[UI_CURRENT]),
+		      (unsigned long long)be64_to_cpu(p->uuids.uuid[UI_BITMAP]),
+		      (unsigned long long)be64_to_cpu(p->uuids.uuid[UI_HISTORY_START]),
+		      (unsigned long long)be64_to_cpu(p->uuids.uuid[UI_HISTORY_END]));
+		break;
+
+	case P_SIZES:
+		INFOP("%s (d %lluMiB, u %lluMiB, c %lldMiB, "
+		      "max bio %x, q order %x)\n",
+		      cmdname(cmd),
+		      (long long)(be64_to_cpu(p->sizes.d_size)>>(20-9)),
+		      (long long)(be64_to_cpu(p->sizes.u_size)>>(20-9)),
+		      (long long)(be64_to_cpu(p->sizes.c_size)>>(20-9)),
+		      be32_to_cpu(p->sizes.max_segment_size),
+		      be32_to_cpu(p->sizes.queue_order_type));
+		break;
+
+	case P_STATE:
+		v.i = be32_to_cpu(p->state.state);
+		m.i = 0xffffffff;
+		dump_st(tmp, sizeof(tmp), m, v);
+		INFOP("%s (s %x {%s})\n", cmdname(cmd), v.i, tmp);
+		break;
+
+	case P_STATE_CHG_REQ:
+		m.i = be32_to_cpu(p->req_state.mask);
+		v.i = be32_to_cpu(p->req_state.val);
+		dump_st(tmp, sizeof(tmp), m, v);
+		INFOP("%s (m %x v %x {%s})\n", cmdname(cmd), m.i, v.i, tmp);
+		break;
+
+	case P_STATE_CHG_REPLY:
+		INFOP("%s (ret %x)\n", cmdname(cmd),
+		      be32_to_cpu(p->req_state_reply.retcode));
+		break;
+
+	case P_PING:
+	case P_PING_ACK:
+		/*
+		 * Dont trace pings at summary level
+		 */
+		if (trace_level < TRACE_LVL_ALL)
+			break;
+		/* fall through... */
+	default:
+		INFOP("%s (%u)\n", cmdname(cmd), cmd);
+		break;
+	}
+}
+
+
+static int __init drbd_trace_init(void)
+{
+	int ret;
+
+	if (trace_mask & TRACE_UNPLUG) {
+		ret = register_trace_drbd_unplug(probe_drbd_unplug);
+		WARN_ON(ret);
+	}
+	if (trace_mask & TRACE_UUID) {
+		ret = register_trace_drbd_uuid(probe_drbd_uuid);
+		WARN_ON(ret);
+	}
+	if (trace_mask & TRACE_EE) {
+		ret = register_trace_drbd_ee(probe_drbd_ee);
+		WARN_ON(ret);
+	}
+	if (trace_mask & TRACE_PACKET) {
+		ret = register_trace_drbd_packet(probe_drbd_packet);
+		WARN_ON(ret);
+	}
+	if (trace_mask & TRACE_MD_IO) {
+		ret = register_trace_drbd_md_io(probe_drbd_md_io);
+		WARN_ON(ret);
+	}
+	if (trace_mask & TRACE_EPOCH) {
+		ret = register_trace_drbd_epoch(probe_drbd_epoch);
+		WARN_ON(ret);
+	}
+	if (trace_mask & TRACE_NL) {
+		ret = register_trace_drbd_netlink(probe_drbd_netlink);
+		WARN_ON(ret);
+	}
+	if (trace_mask & TRACE_AL_EXT) {
+		ret = register_trace_drbd_actlog(probe_drbd_actlog);
+		WARN_ON(ret);
+	}
+	if (trace_mask & TRACE_RQ) {
+		ret = register_trace_drbd_bio(probe_drbd_bio);
+		WARN_ON(ret);
+	}
+	if (trace_mask & TRACE_INT_RQ) {
+		ret = register_trace_drbd_req(probe_drbd_req);
+		WARN_ON(ret);
+	}
+	if (trace_mask & TRACE_RESYNC) {
+		ret = register_trace__drbd_resync(probe_drbd_resync);
+		WARN_ON(ret);
+	}
+	return 0;
+}
+
+module_init(drbd_trace_init);
+
+static void __exit drbd_trace_exit(void)
+{
+	if (trace_mask & TRACE_UNPLUG)
+		unregister_trace_drbd_unplug(probe_drbd_unplug);
+	if (trace_mask & TRACE_UUID)
+		unregister_trace_drbd_uuid(probe_drbd_uuid);
+	if (trace_mask & TRACE_EE)
+		unregister_trace_drbd_ee(probe_drbd_ee);
+	if (trace_mask & TRACE_PACKET)
+		unregister_trace_drbd_packet(probe_drbd_packet);
+	if (trace_mask & TRACE_MD_IO)
+		unregister_trace_drbd_md_io(probe_drbd_md_io);
+	if (trace_mask & TRACE_EPOCH)
+		unregister_trace_drbd_epoch(probe_drbd_epoch);
+	if (trace_mask & TRACE_NL)
+		unregister_trace_drbd_netlink(probe_drbd_netlink);
+	if (trace_mask & TRACE_AL_EXT)
+		unregister_trace_drbd_actlog(probe_drbd_actlog);
+	if (trace_mask & TRACE_RQ)
+		unregister_trace_drbd_bio(probe_drbd_bio);
+	if (trace_mask & TRACE_INT_RQ)
+		unregister_trace_drbd_req(probe_drbd_req);
+	if (trace_mask & TRACE_RESYNC)
+		unregister_trace__drbd_resync(probe_drbd_resync);
+
+	tracepoint_synchronize_unregister();
+}
+
+module_exit(drbd_trace_exit);
diff --git a/drivers/block/drbd/drbd_tracing.h b/drivers/block/drbd/drbd_tracing.h
new file mode 100644
index 00000000000..c4531a137f6
--- /dev/null
+++ b/drivers/block/drbd/drbd_tracing.h
@@ -0,0 +1,87 @@
+/*
+   drbd_tracing.h
+
+   This file is part of DRBD by Philipp Reisner and Lars Ellenberg.
+
+   Copyright (C) 2003-2008, LINBIT Information Technologies GmbH.
+   Copyright (C) 2003-2008, Philipp Reisner <philipp.reisner@linbit.com>.
+   Copyright (C) 2003-2008, Lars Ellenberg <lars.ellenberg@linbit.com>.
+
+   drbd is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 2, or (at your option)
+   any later version.
+
+   drbd is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with drbd; see the file COPYING.  If not, write to
+   the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
+
+ */
+
+#ifndef DRBD_TRACING_H
+#define DRBD_TRACING_H
+
+#include <linux/tracepoint.h>
+#include "drbd_int.h"
+#include "drbd_req.h"
+
+enum {
+	TRACE_LVL_ALWAYS = 0,
+	TRACE_LVL_SUMMARY,
+	TRACE_LVL_METRICS,
+	TRACE_LVL_ALL,
+	TRACE_LVL_MAX
+};
+
+DECLARE_TRACE(drbd_unplug,
+	TP_PROTO(struct drbd_conf *mdev, char* msg),
+	TP_ARGS(mdev, msg));
+
+DECLARE_TRACE(drbd_uuid,
+	TP_PROTO(struct drbd_conf *mdev, enum drbd_uuid_index index),
+	TP_ARGS(mdev, index));
+
+DECLARE_TRACE(drbd_ee,
+	TP_PROTO(struct drbd_conf *mdev, struct drbd_epoch_entry *e, char* msg),
+	TP_ARGS(mdev, e, msg));
+
+DECLARE_TRACE(drbd_md_io,
+	TP_PROTO(struct drbd_conf *mdev, int rw, struct drbd_backing_dev *bdev),
+	TP_ARGS(mdev, rw, bdev));
+
+DECLARE_TRACE(drbd_epoch,
+	TP_PROTO(struct drbd_conf *mdev, struct drbd_epoch *epoch, enum epoch_event ev),
+	TP_ARGS(mdev, epoch, ev));
+
+DECLARE_TRACE(drbd_netlink,
+	TP_PROTO(void *data, int is_req),
+	TP_ARGS(data, is_req));
+
+DECLARE_TRACE(drbd_actlog,
+	TP_PROTO(struct drbd_conf *mdev, sector_t sector, char* msg),
+	TP_ARGS(mdev, sector, msg));
+
+DECLARE_TRACE(drbd_bio,
+	TP_PROTO(struct drbd_conf *mdev, const char *pfx, struct bio *bio, int complete,
+		 struct drbd_request *r),
+	TP_ARGS(mdev, pfx, bio, complete, r));
+
+DECLARE_TRACE(drbd_req,
+	TP_PROTO(struct drbd_request *req, enum drbd_req_event what, char *msg),
+	      TP_ARGS(req, what, msg));
+
+DECLARE_TRACE(drbd_packet,
+	TP_PROTO(struct drbd_conf *mdev, struct socket *sock,
+		 int recv, union p_polymorph *p, char *file, int line),
+	TP_ARGS(mdev, sock, recv, p, file, line));
+
+DECLARE_TRACE(_drbd_resync,
+	TP_PROTO(struct drbd_conf *mdev, int level, const char *fmt, va_list args),
+	TP_ARGS(mdev, level, fmt, args));
+
+#endif
diff --git a/drivers/block/drbd/drbd_vli.h b/drivers/block/drbd/drbd_vli.h
new file mode 100644
index 00000000000..fc824006e72
--- /dev/null
+++ b/drivers/block/drbd/drbd_vli.h
@@ -0,0 +1,351 @@
+/*
+-*- linux-c -*-
+   drbd_receiver.c
+   This file is part of DRBD by Philipp Reisner and Lars Ellenberg.
+
+   Copyright (C) 2001-2008, LINBIT Information Technologies GmbH.
+   Copyright (C) 1999-2008, Philipp Reisner <philipp.reisner@linbit.com>.
+   Copyright (C) 2002-2008, Lars Ellenberg <lars.ellenberg@linbit.com>.
+
+   drbd is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 2, or (at your option)
+   any later version.
+
+   drbd is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with drbd; see the file COPYING.  If not, write to
+   the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#ifndef _DRBD_VLI_H
+#define _DRBD_VLI_H
+
+/*
+ * At a granularity of 4KiB storage represented per bit,
+ * and stroage sizes of several TiB,
+ * and possibly small-bandwidth replication,
+ * the bitmap transfer time can take much too long,
+ * if transmitted in plain text.
+ *
+ * We try to reduce the transfered bitmap information
+ * by encoding runlengths of bit polarity.
+ *
+ * We never actually need to encode a "zero" (runlengths are positive).
+ * But then we have to store the value of the first bit.
+ * The first bit of information thus shall encode if the first runlength
+ * gives the number of set or unset bits.
+ *
+ * We assume that large areas are either completely set or unset,
+ * which gives good compression with any runlength method,
+ * even when encoding the runlength as fixed size 32bit/64bit integers.
+ *
+ * Still, there may be areas where the polarity flips every few bits,
+ * and encoding the runlength sequence of those areas with fix size
+ * integers would be much worse than plaintext.
+ *
+ * We want to encode small runlength values with minimum code length,
+ * while still being able to encode a Huge run of all zeros.
+ *
+ * Thus we need a Variable Length Integer encoding, VLI.
+ *
+ * For some cases, we produce more code bits than plaintext input.
+ * We need to send incompressible chunks as plaintext, skip over them
+ * and then see if the next chunk compresses better.
+ *
+ * We don't care too much about "excellent" compression ratio for large
+ * runlengths (all set/all clear): whether we achieve a factor of 100
+ * or 1000 is not that much of an issue.
+ * We do not want to waste too much on short runlengths in the "noisy"
+ * parts of the bitmap, though.
+ *
+ * There are endless variants of VLI, we experimented with:
+ *  * simple byte-based
+ *  * various bit based with different code word length.
+ *
+ * To avoid yet an other configuration parameter (choice of bitmap compression
+ * algorithm) which was difficult to explain and tune, we just chose the one
+ * variant that turned out best in all test cases.
+ * Based on real world usage patterns, with device sizes ranging from a few GiB
+ * to several TiB, file server/mailserver/webserver/mysql/postgress,
+ * mostly idle to really busy, the all time winner (though sometimes only
+ * marginally better) is:
+ */
+
+/*
+ * encoding is "visualised" as
+ * __little endian__ bitstream, least significant bit first (left most)
+ *
+ * this particular encoding is chosen so that the prefix code
+ * starts as unary encoding the level, then modified so that
+ * 10 levels can be described in 8bit, with minimal overhead
+ * for the smaller levels.
+ *
+ * Number of data bits follow fibonacci sequence, with the exception of the
+ * last level (+1 data bit, so it makes 64bit total).  The only worse code when
+ * encoding bit polarity runlength is 1 plain bits => 2 code bits.
+prefix    data bits                                    max val  Nº data bits
+0 x                                                         0x2            1
+10 x                                                        0x4            1
+110 xx                                                      0x8            2
+1110 xxx                                                   0x10            3
+11110 xxx xx                                               0x30            5
+111110 xx xxxxxx                                          0x130            8
+11111100  xxxxxxxx xxxxx                                 0x2130           13
+11111110  xxxxxxxx xxxxxxxx xxxxx                      0x202130           21
+11111101  xxxxxxxx xxxxxxxx xxxxxxxx  xxxxxxxx xx   0x400202130           34
+11111111  xxxxxxxx xxxxxxxx xxxxxxxx  xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx 56
+ * maximum encodable value: 0x100000400202130 == 2**56 + some */
+
+/* compression "table":
+ transmitted   x                                0.29
+ as plaintext x                                  ........................
+             x                                   ........................
+            x                                    ........................
+           x    0.59                         0.21........................
+          x      ........................................................
+         x       .. c ...................................................
+        x    0.44.. o ...................................................
+       x .......... d ...................................................
+      x  .......... e ...................................................
+     X.............   ...................................................
+    x.............. b ...................................................
+2.0x............... i ...................................................
+ #X................ t ...................................................
+ #................. s ...........................  plain bits  ..........
+-+-----------------------------------------------------------------------
+ 1             16              32                              64
+*/
+
+/* LEVEL: (total bits, prefix bits, prefix value),
+ * sorted ascending by number of total bits.
+ * The rest of the code table is calculated at compiletime from this. */
+
+/* fibonacci data 1, 1, ... */
+#define VLI_L_1_1() do { \
+	LEVEL( 2, 1, 0x00); \
+	LEVEL( 3, 2, 0x01); \
+	LEVEL( 5, 3, 0x03); \
+	LEVEL( 7, 4, 0x07); \
+	LEVEL(10, 5, 0x0f); \
+	LEVEL(14, 6, 0x1f); \
+	LEVEL(21, 8, 0x3f); \
+	LEVEL(29, 8, 0x7f); \
+	LEVEL(42, 8, 0xbf); \
+	LEVEL(64, 8, 0xff); \
+	} while (0)
+
+/* finds a suitable level to decode the least significant part of in.
+ * returns number of bits consumed.
+ *
+ * BUG() for bad input, as that would mean a buggy code table. */
+static inline int vli_decode_bits(u64 *out, const u64 in)
+{
+	u64 adj = 1;
+
+#define LEVEL(t,b,v)					\
+	do {						\
+		if ((in & ((1 << b) -1)) == v) {	\
+			*out = ((in & ((~0ULL) >> (64-t))) >> b) + adj;	\
+			return t;			\
+		}					\
+		adj += 1ULL << (t - b);			\
+	} while (0)
+
+	VLI_L_1_1();
+
+	/* NOT REACHED, if VLI_LEVELS code table is defined properly */
+	BUG();
+#undef LEVEL
+}
+
+/* return number of code bits needed,
+ * or negative error number */
+static inline int __vli_encode_bits(u64 *out, const u64 in)
+{
+	u64 max = 0;
+	u64 adj = 1;
+
+	if (in == 0)
+		return -EINVAL;
+
+#define LEVEL(t,b,v) do {		\
+		max += 1ULL << (t - b);	\
+		if (in <= max) {	\
+			if (out)	\
+				*out = ((in - adj) << b) | v;	\
+			return t;	\
+		}			\
+		adj = max + 1;		\
+	} while (0)
+
+	VLI_L_1_1();
+
+	return -EOVERFLOW;
+#undef LEVEL
+}
+
+#undef VLI_L_1_1
+
+/* code from here down is independend of actually used bit code */
+
+/*
+ * Code length is determined by some unique (e.g. unary) prefix.
+ * This encodes arbitrary bit length, not whole bytes: we have a bit-stream,
+ * not a byte stream.
+ */
+
+/* for the bitstream, we need a cursor */
+struct bitstream_cursor {
+	/* the current byte */
+	u8 *b;
+	/* the current bit within *b, nomalized: 0..7 */
+	unsigned int bit;
+};
+
+/* initialize cursor to point to first bit of stream */
+static inline void bitstream_cursor_reset(struct bitstream_cursor *cur, void *s)
+{
+	cur->b = s;
+	cur->bit = 0;
+}
+
+/* advance cursor by that many bits; maximum expected input value: 64,
+ * but depending on VLI implementation, it may be more. */
+static inline void bitstream_cursor_advance(struct bitstream_cursor *cur, unsigned int bits)
+{
+	bits += cur->bit;
+	cur->b = cur->b + (bits >> 3);
+	cur->bit = bits & 7;
+}
+
+/* the bitstream itself knows its length */
+struct bitstream {
+	struct bitstream_cursor cur;
+	unsigned char *buf;
+	size_t buf_len;		/* in bytes */
+
+	/* for input stream:
+	 * number of trailing 0 bits for padding
+	 * total number of valid bits in stream: buf_len * 8 - pad_bits */
+	unsigned int pad_bits;
+};
+
+static inline void bitstream_init(struct bitstream *bs, void *s, size_t len, unsigned int pad_bits)
+{
+	bs->buf = s;
+	bs->buf_len = len;
+	bs->pad_bits = pad_bits;
+	bitstream_cursor_reset(&bs->cur, bs->buf);
+}
+
+static inline void bitstream_rewind(struct bitstream *bs)
+{
+	bitstream_cursor_reset(&bs->cur, bs->buf);
+	memset(bs->buf, 0, bs->buf_len);
+}
+
+/* Put (at most 64) least significant bits of val into bitstream, and advance cursor.
+ * Ignores "pad_bits".
+ * Returns zero if bits == 0 (nothing to do).
+ * Returns number of bits used if successful.
+ *
+ * If there is not enough room left in bitstream,
+ * leaves bitstream unchanged and returns -ENOBUFS.
+ */
+static inline int bitstream_put_bits(struct bitstream *bs, u64 val, const unsigned int bits)
+{
+	unsigned char *b = bs->cur.b;
+	unsigned int tmp;
+
+	if (bits == 0)
+		return 0;
+
+	if ((bs->cur.b + ((bs->cur.bit + bits -1) >> 3)) - bs->buf >= bs->buf_len)
+		return -ENOBUFS;
+
+	/* paranoia: strip off hi bits; they should not be set anyways. */
+	if (bits < 64)
+		val &= ~0ULL >> (64 - bits);
+
+	*b++ |= (val & 0xff) << bs->cur.bit;
+
+	for (tmp = 8 - bs->cur.bit; tmp < bits; tmp += 8)
+		*b++ |= (val >> tmp) & 0xff;
+
+	bitstream_cursor_advance(&bs->cur, bits);
+	return bits;
+}
+
+/* Fetch (at most 64) bits from bitstream into *out, and advance cursor.
+ *
+ * If more than 64 bits are requested, returns -EINVAL and leave *out unchanged.
+ *
+ * If there are less than the requested number of valid bits left in the
+ * bitstream, still fetches all available bits.
+ *
+ * Returns number of actually fetched bits.
+ */
+static inline int bitstream_get_bits(struct bitstream *bs, u64 *out, int bits)
+{
+	u64 val;
+	unsigned int n;
+
+	if (bits > 64)
+		return -EINVAL;
+
+	if (bs->cur.b + ((bs->cur.bit + bs->pad_bits + bits -1) >> 3) - bs->buf >= bs->buf_len)
+		bits = ((bs->buf_len - (bs->cur.b - bs->buf)) << 3)
+			- bs->cur.bit - bs->pad_bits;
+
+	if (bits == 0) {
+		*out = 0;
+		return 0;
+	}
+
+	/* get the high bits */
+	val = 0;
+	n = (bs->cur.bit + bits + 7) >> 3;
+	/* n may be at most 9, if cur.bit + bits > 64 */
+	/* which means this copies at most 8 byte */
+	if (n) {
+		memcpy(&val, bs->cur.b+1, n - 1);
+		val = le64_to_cpu(val) << (8 - bs->cur.bit);
+	}
+
+	/* we still need the low bits */
+	val |= bs->cur.b[0] >> bs->cur.bit;
+
+	/* and mask out bits we don't want */
+	val &= ~0ULL >> (64 - bits);
+
+	bitstream_cursor_advance(&bs->cur, bits);
+	*out = val;
+
+	return bits;
+}
+
+/* encodes @in as vli into @bs;
+
+ * return values
+ *  > 0: number of bits successfully stored in bitstream
+ * -ENOBUFS @bs is full
+ * -EINVAL input zero (invalid)
+ * -EOVERFLOW input too large for this vli code (invalid)
+ */
+static inline int vli_encode_bits(struct bitstream *bs, u64 in)
+{
+	u64 code = code;
+	int bits = __vli_encode_bits(&code, in);
+
+	if (bits <= 0)
+		return bits;
+
+	return bitstream_put_bits(bs, code, bits);
+}
+
+#endif
diff --git a/drivers/block/drbd/drbd_worker.c b/drivers/block/drbd/drbd_worker.c
new file mode 100644
index 00000000000..212e9545e63
--- /dev/null
+++ b/drivers/block/drbd/drbd_worker.c
@@ -0,0 +1,1529 @@
+/*
+   drbd_worker.c
+
+   This file is part of DRBD by Philipp Reisner and Lars Ellenberg.
+
+   Copyright (C) 2001-2008, LINBIT Information Technologies GmbH.
+   Copyright (C) 1999-2008, Philipp Reisner <philipp.reisner@linbit.com>.
+   Copyright (C) 2002-2008, Lars Ellenberg <lars.ellenberg@linbit.com>.
+
+   drbd is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 2, or (at your option)
+   any later version.
+
+   drbd is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with drbd; see the file COPYING.  If not, write to
+   the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
+
+ */
+
+#include <linux/autoconf.h>
+#include <linux/module.h>
+#include <linux/version.h>
+#include <linux/drbd.h>
+#include <linux/sched.h>
+#include <linux/smp_lock.h>
+#include <linux/wait.h>
+#include <linux/mm.h>
+#include <linux/memcontrol.h>
+#include <linux/mm_inline.h>
+#include <linux/slab.h>
+#include <linux/random.h>
+#include <linux/mm.h>
+#include <linux/string.h>
+#include <linux/scatterlist.h>
+
+#include "drbd_int.h"
+#include "drbd_req.h"
+#include "drbd_tracing.h"
+
+#define SLEEP_TIME (HZ/10)
+
+static int w_make_ov_request(struct drbd_conf *mdev, struct drbd_work *w, int cancel);
+
+
+
+/* defined here:
+   drbd_md_io_complete
+   drbd_endio_write_sec
+   drbd_endio_read_sec
+   drbd_endio_pri
+
+ * more endio handlers:
+   atodb_endio in drbd_actlog.c
+   drbd_bm_async_io_complete in drbd_bitmap.c
+
+ * For all these callbacks, note the following:
+ * The callbacks will be called in irq context by the IDE drivers,
+ * and in Softirqs/Tasklets/BH context by the SCSI drivers.
+ * Try to get the locking right :)
+ *
+ */
+
+
+/* About the global_state_lock
+   Each state transition on an device holds a read lock. In case we have
+   to evaluate the sync after dependencies, we grab a write lock, because
+   we need stable states on all devices for that.  */
+rwlock_t global_state_lock;
+
+/* used for synchronous meta data and bitmap IO
+ * submitted by drbd_md_sync_page_io()
+ */
+void drbd_md_io_complete(struct bio *bio, int error)
+{
+	struct drbd_md_io *md_io;
+
+	md_io = (struct drbd_md_io *)bio->bi_private;
+	md_io->error = error;
+
+	trace_drbd_bio(md_io->mdev, "Md", bio, 1, NULL);
+
+	complete(&md_io->event);
+}
+
+/* reads on behalf of the partner,
+ * "submitted" by the receiver
+ */
+void drbd_endio_read_sec(struct bio *bio, int error) __releases(local)
+{
+	unsigned long flags = 0;
+	struct drbd_epoch_entry *e = NULL;
+	struct drbd_conf *mdev;
+	int uptodate = bio_flagged(bio, BIO_UPTODATE);
+
+	e = bio->bi_private;
+	mdev = e->mdev;
+
+	if (error)
+		dev_warn(DEV, "read: error=%d s=%llus\n", error,
+				(unsigned long long)e->sector);
+	if (!error && !uptodate) {
+		dev_warn(DEV, "read: setting error to -EIO s=%llus\n",
+				(unsigned long long)e->sector);
+		/* strange behavior of some lower level drivers...
+		 * fail the request by clearing the uptodate flag,
+		 * but do not return any error?! */
+		error = -EIO;
+	}
+
+	D_ASSERT(e->block_id != ID_VACANT);
+
+	trace_drbd_bio(mdev, "Sec", bio, 1, NULL);
+
+	spin_lock_irqsave(&mdev->req_lock, flags);
+	mdev->read_cnt += e->size >> 9;
+	list_del(&e->w.list);
+	if (list_empty(&mdev->read_ee))
+		wake_up(&mdev->ee_wait);
+	spin_unlock_irqrestore(&mdev->req_lock, flags);
+
+	drbd_chk_io_error(mdev, error, FALSE);
+	drbd_queue_work(&mdev->data.work, &e->w);
+	put_ldev(mdev);
+
+	trace_drbd_ee(mdev, e, "read completed");
+}
+
+/* writes on behalf of the partner, or resync writes,
+ * "submitted" by the receiver.
+ */
+void drbd_endio_write_sec(struct bio *bio, int error) __releases(local)
+{
+	unsigned long flags = 0;
+	struct drbd_epoch_entry *e = NULL;
+	struct drbd_conf *mdev;
+	sector_t e_sector;
+	int do_wake;
+	int is_syncer_req;
+	int do_al_complete_io;
+	int uptodate = bio_flagged(bio, BIO_UPTODATE);
+	int is_barrier = bio_rw_flagged(bio, BIO_RW_BARRIER);
+
+	e = bio->bi_private;
+	mdev = e->mdev;
+
+	if (error)
+		dev_warn(DEV, "write: error=%d s=%llus\n", error,
+				(unsigned long long)e->sector);
+	if (!error && !uptodate) {
+		dev_warn(DEV, "write: setting error to -EIO s=%llus\n",
+				(unsigned long long)e->sector);
+		/* strange behavior of some lower level drivers...
+		 * fail the request by clearing the uptodate flag,
+		 * but do not return any error?! */
+		error = -EIO;
+	}
+
+	/* error == -ENOTSUPP would be a better test,
+	 * alas it is not reliable */
+	if (error && is_barrier && e->flags & EE_IS_BARRIER) {
+		drbd_bump_write_ordering(mdev, WO_bdev_flush);
+		spin_lock_irqsave(&mdev->req_lock, flags);
+		list_del(&e->w.list);
+		e->w.cb = w_e_reissue;
+		/* put_ldev actually happens below, once we come here again. */
+		__release(local);
+		spin_unlock_irqrestore(&mdev->req_lock, flags);
+		drbd_queue_work(&mdev->data.work, &e->w);
+		return;
+	}
+
+	D_ASSERT(e->block_id != ID_VACANT);
+
+	trace_drbd_bio(mdev, "Sec", bio, 1, NULL);
+
+	spin_lock_irqsave(&mdev->req_lock, flags);
+	mdev->writ_cnt += e->size >> 9;
+	is_syncer_req = is_syncer_block_id(e->block_id);
+
+	/* after we moved e to done_ee,
+	 * we may no longer access it,
+	 * it may be freed/reused already!
+	 * (as soon as we release the req_lock) */
+	e_sector = e->sector;
+	do_al_complete_io = e->flags & EE_CALL_AL_COMPLETE_IO;
+
+	list_del(&e->w.list); /* has been on active_ee or sync_ee */
+	list_add_tail(&e->w.list, &mdev->done_ee);
+
+	trace_drbd_ee(mdev, e, "write completed");
+
+	/* No hlist_del_init(&e->colision) here, we did not send the Ack yet,
+	 * neither did we wake possibly waiting conflicting requests.
+	 * done from "drbd_process_done_ee" within the appropriate w.cb
+	 * (e_end_block/e_end_resync_block) or from _drbd_clear_done_ee */
+
+	do_wake = is_syncer_req
+		? list_empty(&mdev->sync_ee)
+		: list_empty(&mdev->active_ee);
+
+	if (error)
+		__drbd_chk_io_error(mdev, FALSE);
+	spin_unlock_irqrestore(&mdev->req_lock, flags);
+
+	if (is_syncer_req)
+		drbd_rs_complete_io(mdev, e_sector);
+
+	if (do_wake)
+		wake_up(&mdev->ee_wait);
+
+	if (do_al_complete_io)
+		drbd_al_complete_io(mdev, e_sector);
+
+	wake_asender(mdev);
+	put_ldev(mdev);
+
+}
+
+/* read, readA or write requests on R_PRIMARY coming from drbd_make_request
+ */
+void drbd_endio_pri(struct bio *bio, int error)
+{
+	unsigned long flags;
+	struct drbd_request *req = bio->bi_private;
+	struct drbd_conf *mdev = req->mdev;
+	struct bio_and_error m;
+	enum drbd_req_event what;
+	int uptodate = bio_flagged(bio, BIO_UPTODATE);
+
+	if (error)
+		dev_warn(DEV, "p %s: error=%d\n",
+			 bio_data_dir(bio) == WRITE ? "write" : "read", error);
+	if (!error && !uptodate) {
+		dev_warn(DEV, "p %s: setting error to -EIO\n",
+			 bio_data_dir(bio) == WRITE ? "write" : "read");
+		/* strange behavior of some lower level drivers...
+		 * fail the request by clearing the uptodate flag,
+		 * but do not return any error?! */
+		error = -EIO;
+	}
+
+	trace_drbd_bio(mdev, "Pri", bio, 1, NULL);
+
+	/* to avoid recursion in __req_mod */
+	if (unlikely(error)) {
+		what = (bio_data_dir(bio) == WRITE)
+			? write_completed_with_error
+			: (bio_rw(bio) == READA)
+			  ? read_completed_with_error
+			  : read_ahead_completed_with_error;
+	} else
+		what = completed_ok;
+
+	bio_put(req->private_bio);
+	req->private_bio = ERR_PTR(error);
+
+	spin_lock_irqsave(&mdev->req_lock, flags);
+	__req_mod(req, what, &m);
+	spin_unlock_irqrestore(&mdev->req_lock, flags);
+
+	if (m.bio)
+		complete_master_bio(mdev, &m);
+}
+
+int w_io_error(struct drbd_conf *mdev, struct drbd_work *w, int cancel)
+{
+	struct drbd_request *req = container_of(w, struct drbd_request, w);
+
+	/* NOTE: mdev->ldev can be NULL by the time we get here! */
+	/* D_ASSERT(mdev->ldev->dc.on_io_error != EP_PASS_ON); */
+
+	/* the only way this callback is scheduled is from _req_may_be_done,
+	 * when it is done and had a local write error, see comments there */
+	drbd_req_free(req);
+
+	return TRUE;
+}
+
+int w_read_retry_remote(struct drbd_conf *mdev, struct drbd_work *w, int cancel)
+{
+	struct drbd_request *req = container_of(w, struct drbd_request, w);
+
+	/* We should not detach for read io-error,
+	 * but try to WRITE the P_DATA_REPLY to the failed location,
+	 * to give the disk the chance to relocate that block */
+
+	spin_lock_irq(&mdev->req_lock);
+	if (cancel ||
+	    mdev->state.conn < C_CONNECTED ||
+	    mdev->state.pdsk <= D_INCONSISTENT) {
+		_req_mod(req, send_canceled);
+		spin_unlock_irq(&mdev->req_lock);
+		dev_alert(DEV, "WE ARE LOST. Local IO failure, no peer.\n");
+		return 1;
+	}
+	spin_unlock_irq(&mdev->req_lock);
+
+	return w_send_read_req(mdev, w, 0);
+}
+
+int w_resync_inactive(struct drbd_conf *mdev, struct drbd_work *w, int cancel)
+{
+	ERR_IF(cancel) return 1;
+	dev_err(DEV, "resync inactive, but callback triggered??\n");
+	return 1; /* Simply ignore this! */
+}
+
+void drbd_csum(struct drbd_conf *mdev, struct crypto_hash *tfm, struct bio *bio, void *digest)
+{
+	struct hash_desc desc;
+	struct scatterlist sg;
+	struct bio_vec *bvec;
+	int i;
+
+	desc.tfm = tfm;
+	desc.flags = 0;
+
+	sg_init_table(&sg, 1);
+	crypto_hash_init(&desc);
+
+	__bio_for_each_segment(bvec, bio, i, 0) {
+		sg_set_page(&sg, bvec->bv_page, bvec->bv_len, bvec->bv_offset);
+		crypto_hash_update(&desc, &sg, sg.length);
+	}
+	crypto_hash_final(&desc, digest);
+}
+
+static int w_e_send_csum(struct drbd_conf *mdev, struct drbd_work *w, int cancel)
+{
+	struct drbd_epoch_entry *e = container_of(w, struct drbd_epoch_entry, w);
+	int digest_size;
+	void *digest;
+	int ok;
+
+	D_ASSERT(e->block_id == DRBD_MAGIC + 0xbeef);
+
+	if (unlikely(cancel)) {
+		drbd_free_ee(mdev, e);
+		return 1;
+	}
+
+	if (likely(drbd_bio_uptodate(e->private_bio))) {
+		digest_size = crypto_hash_digestsize(mdev->csums_tfm);
+		digest = kmalloc(digest_size, GFP_NOIO);
+		if (digest) {
+			drbd_csum(mdev, mdev->csums_tfm, e->private_bio, digest);
+
+			inc_rs_pending(mdev);
+			ok = drbd_send_drequest_csum(mdev,
+						     e->sector,
+						     e->size,
+						     digest,
+						     digest_size,
+						     P_CSUM_RS_REQUEST);
+			kfree(digest);
+		} else {
+			dev_err(DEV, "kmalloc() of digest failed.\n");
+			ok = 0;
+		}
+	} else
+		ok = 1;
+
+	drbd_free_ee(mdev, e);
+
+	if (unlikely(!ok))
+		dev_err(DEV, "drbd_send_drequest(..., csum) failed\n");
+	return ok;
+}
+
+#define GFP_TRY	(__GFP_HIGHMEM | __GFP_NOWARN)
+
+static int read_for_csum(struct drbd_conf *mdev, sector_t sector, int size)
+{
+	struct drbd_epoch_entry *e;
+
+	if (!get_ldev(mdev))
+		return 0;
+
+	/* GFP_TRY, because if there is no memory available right now, this may
+	 * be rescheduled for later. It is "only" background resync, after all. */
+	e = drbd_alloc_ee(mdev, DRBD_MAGIC+0xbeef, sector, size, GFP_TRY);
+	if (!e) {
+		put_ldev(mdev);
+		return 2;
+	}
+
+	spin_lock_irq(&mdev->req_lock);
+	list_add(&e->w.list, &mdev->read_ee);
+	spin_unlock_irq(&mdev->req_lock);
+
+	e->private_bio->bi_end_io = drbd_endio_read_sec;
+	e->private_bio->bi_rw = READ;
+	e->w.cb = w_e_send_csum;
+
+	mdev->read_cnt += size >> 9;
+	drbd_generic_make_request(mdev, DRBD_FAULT_RS_RD, e->private_bio);
+
+	return 1;
+}
+
+void resync_timer_fn(unsigned long data)
+{
+	unsigned long flags;
+	struct drbd_conf *mdev = (struct drbd_conf *) data;
+	int queue;
+
+	spin_lock_irqsave(&mdev->req_lock, flags);
+
+	if (likely(!test_and_clear_bit(STOP_SYNC_TIMER, &mdev->flags))) {
+		queue = 1;
+		if (mdev->state.conn == C_VERIFY_S)
+			mdev->resync_work.cb = w_make_ov_request;
+		else
+			mdev->resync_work.cb = w_make_resync_request;
+	} else {
+		queue = 0;
+		mdev->resync_work.cb = w_resync_inactive;
+	}
+
+	spin_unlock_irqrestore(&mdev->req_lock, flags);
+
+	/* harmless race: list_empty outside data.work.q_lock */
+	if (list_empty(&mdev->resync_work.list) && queue)
+		drbd_queue_work(&mdev->data.work, &mdev->resync_work);
+}
+
+int w_make_resync_request(struct drbd_conf *mdev,
+		struct drbd_work *w, int cancel)
+{
+	unsigned long bit;
+	sector_t sector;
+	const sector_t capacity = drbd_get_capacity(mdev->this_bdev);
+	int max_segment_size = queue_max_segment_size(mdev->rq_queue);
+	int number, i, size, pe, mx;
+	int align, queued, sndbuf;
+
+	if (unlikely(cancel))
+		return 1;
+
+	if (unlikely(mdev->state.conn < C_CONNECTED)) {
+		dev_err(DEV, "Confused in w_make_resync_request()! cstate < Connected");
+		return 0;
+	}
+
+	if (mdev->state.conn != C_SYNC_TARGET)
+		dev_err(DEV, "%s in w_make_resync_request\n",
+			drbd_conn_str(mdev->state.conn));
+
+	if (!get_ldev(mdev)) {
+		/* Since we only need to access mdev->rsync a
+		   get_ldev_if_state(mdev,D_FAILED) would be sufficient, but
+		   to continue resync with a broken disk makes no sense at
+		   all */
+		dev_err(DEV, "Disk broke down during resync!\n");
+		mdev->resync_work.cb = w_resync_inactive;
+		return 1;
+	}
+
+	number = SLEEP_TIME * mdev->sync_conf.rate / ((BM_BLOCK_SIZE/1024)*HZ);
+	pe = atomic_read(&mdev->rs_pending_cnt);
+
+	mutex_lock(&mdev->data.mutex);
+	if (mdev->data.socket)
+		mx = mdev->data.socket->sk->sk_rcvbuf / sizeof(struct p_block_req);
+	else
+		mx = 1;
+	mutex_unlock(&mdev->data.mutex);
+
+	/* For resync rates >160MB/sec, allow more pending RS requests */
+	if (number > mx)
+		mx = number;
+
+	/* Limit the number of pending RS requests to no more than the peer's receive buffer */
+	if ((pe + number) > mx) {
+		number = mx - pe;
+	}
+
+	for (i = 0; i < number; i++) {
+		/* Stop generating RS requests, when half of the send buffer is filled */
+		mutex_lock(&mdev->data.mutex);
+		if (mdev->data.socket) {
+			queued = mdev->data.socket->sk->sk_wmem_queued;
+			sndbuf = mdev->data.socket->sk->sk_sndbuf;
+		} else {
+			queued = 1;
+			sndbuf = 0;
+		}
+		mutex_unlock(&mdev->data.mutex);
+		if (queued > sndbuf / 2)
+			goto requeue;
+
+next_sector:
+		size = BM_BLOCK_SIZE;
+		bit  = drbd_bm_find_next(mdev, mdev->bm_resync_fo);
+
+		if (bit == -1UL) {
+			mdev->bm_resync_fo = drbd_bm_bits(mdev);
+			mdev->resync_work.cb = w_resync_inactive;
+			put_ldev(mdev);
+			return 1;
+		}
+
+		sector = BM_BIT_TO_SECT(bit);
+
+		if (drbd_try_rs_begin_io(mdev, sector)) {
+			mdev->bm_resync_fo = bit;
+			goto requeue;
+		}
+		mdev->bm_resync_fo = bit + 1;
+
+		if (unlikely(drbd_bm_test_bit(mdev, bit) == 0)) {
+			drbd_rs_complete_io(mdev, sector);
+			goto next_sector;
+		}
+
+#if DRBD_MAX_SEGMENT_SIZE > BM_BLOCK_SIZE
+		/* try to find some adjacent bits.
+		 * we stop if we have already the maximum req size.
+		 *
+		 * Additionally always align bigger requests, in order to
+		 * be prepared for all stripe sizes of software RAIDs.
+		 *
+		 * we _do_ care about the agreed-upon q->max_segment_size
+		 * here, as splitting up the requests on the other side is more
+		 * difficult.  the consequence is, that on lvm and md and other
+		 * "indirect" devices, this is dead code, since
+		 * q->max_segment_size will be PAGE_SIZE.
+		 */
+		align = 1;
+		for (;;) {
+			if (size + BM_BLOCK_SIZE > max_segment_size)
+				break;
+
+			/* Be always aligned */
+			if (sector & ((1<<(align+3))-1))
+				break;
+
+			/* do not cross extent boundaries */
+			if (((bit+1) & BM_BLOCKS_PER_BM_EXT_MASK) == 0)
+				break;
+			/* now, is it actually dirty, after all?
+			 * caution, drbd_bm_test_bit is tri-state for some
+			 * obscure reason; ( b == 0 ) would get the out-of-band
+			 * only accidentally right because of the "oddly sized"
+			 * adjustment below */
+			if (drbd_bm_test_bit(mdev, bit+1) != 1)
+				break;
+			bit++;
+			size += BM_BLOCK_SIZE;
+			if ((BM_BLOCK_SIZE << align) <= size)
+				align++;
+			i++;
+		}
+		/* if we merged some,
+		 * reset the offset to start the next drbd_bm_find_next from */
+		if (size > BM_BLOCK_SIZE)
+			mdev->bm_resync_fo = bit + 1;
+#endif
+
+		/* adjust very last sectors, in case we are oddly sized */
+		if (sector + (size>>9) > capacity)
+			size = (capacity-sector)<<9;
+		if (mdev->agreed_pro_version >= 89 && mdev->csums_tfm) {
+			switch (read_for_csum(mdev, sector, size)) {
+			case 0: /* Disk failure*/
+				put_ldev(mdev);
+				return 0;
+			case 2: /* Allocation failed */
+				drbd_rs_complete_io(mdev, sector);
+				mdev->bm_resync_fo = BM_SECT_TO_BIT(sector);
+				goto requeue;
+			/* case 1: everything ok */
+			}
+		} else {
+			inc_rs_pending(mdev);
+			if (!drbd_send_drequest(mdev, P_RS_DATA_REQUEST,
+					       sector, size, ID_SYNCER)) {
+				dev_err(DEV, "drbd_send_drequest() failed, aborting...\n");
+				dec_rs_pending(mdev);
+				put_ldev(mdev);
+				return 0;
+			}
+		}
+	}
+
+	if (mdev->bm_resync_fo >= drbd_bm_bits(mdev)) {
+		/* last syncer _request_ was sent,
+		 * but the P_RS_DATA_REPLY not yet received.  sync will end (and
+		 * next sync group will resume), as soon as we receive the last
+		 * resync data block, and the last bit is cleared.
+		 * until then resync "work" is "inactive" ...
+		 */
+		mdev->resync_work.cb = w_resync_inactive;
+		put_ldev(mdev);
+		return 1;
+	}
+
+ requeue:
+	mod_timer(&mdev->resync_timer, jiffies + SLEEP_TIME);
+	put_ldev(mdev);
+	return 1;
+}
+
+static int w_make_ov_request(struct drbd_conf *mdev, struct drbd_work *w, int cancel)
+{
+	int number, i, size;
+	sector_t sector;
+	const sector_t capacity = drbd_get_capacity(mdev->this_bdev);
+
+	if (unlikely(cancel))
+		return 1;
+
+	if (unlikely(mdev->state.conn < C_CONNECTED)) {
+		dev_err(DEV, "Confused in w_make_ov_request()! cstate < Connected");
+		return 0;
+	}
+
+	number = SLEEP_TIME*mdev->sync_conf.rate / ((BM_BLOCK_SIZE/1024)*HZ);
+	if (atomic_read(&mdev->rs_pending_cnt) > number)
+		goto requeue;
+
+	number -= atomic_read(&mdev->rs_pending_cnt);
+
+	sector = mdev->ov_position;
+	for (i = 0; i < number; i++) {
+		if (sector >= capacity) {
+			mdev->resync_work.cb = w_resync_inactive;
+			return 1;
+		}
+
+		size = BM_BLOCK_SIZE;
+
+		if (drbd_try_rs_begin_io(mdev, sector)) {
+			mdev->ov_position = sector;
+			goto requeue;
+		}
+
+		if (sector + (size>>9) > capacity)
+			size = (capacity-sector)<<9;
+
+		inc_rs_pending(mdev);
+		if (!drbd_send_ov_request(mdev, sector, size)) {
+			dec_rs_pending(mdev);
+			return 0;
+		}
+		sector += BM_SECT_PER_BIT;
+	}
+	mdev->ov_position = sector;
+
+ requeue:
+	mod_timer(&mdev->resync_timer, jiffies + SLEEP_TIME);
+	return 1;
+}
+
+
+int w_ov_finished(struct drbd_conf *mdev, struct drbd_work *w, int cancel)
+{
+	kfree(w);
+	ov_oos_print(mdev);
+	drbd_resync_finished(mdev);
+
+	return 1;
+}
+
+static int w_resync_finished(struct drbd_conf *mdev, struct drbd_work *w, int cancel)
+{
+	kfree(w);
+
+	drbd_resync_finished(mdev);
+
+	return 1;
+}
+
+int drbd_resync_finished(struct drbd_conf *mdev)
+{
+	unsigned long db, dt, dbdt;
+	unsigned long n_oos;
+	union drbd_state os, ns;
+	struct drbd_work *w;
+	char *khelper_cmd = NULL;
+
+	/* Remove all elements from the resync LRU. Since future actions
+	 * might set bits in the (main) bitmap, then the entries in the
+	 * resync LRU would be wrong. */
+	if (drbd_rs_del_all(mdev)) {
+		/* In case this is not possible now, most probably because
+		 * there are P_RS_DATA_REPLY Packets lingering on the worker's
+		 * queue (or even the read operations for those packets
+		 * is not finished by now).   Retry in 100ms. */
+
+		drbd_kick_lo(mdev);
+		__set_current_state(TASK_INTERRUPTIBLE);
+		schedule_timeout(HZ / 10);
+		w = kmalloc(sizeof(struct drbd_work), GFP_ATOMIC);
+		if (w) {
+			w->cb = w_resync_finished;
+			drbd_queue_work(&mdev->data.work, w);
+			return 1;
+		}
+		dev_err(DEV, "Warn failed to drbd_rs_del_all() and to kmalloc(w).\n");
+	}
+
+	dt = (jiffies - mdev->rs_start - mdev->rs_paused) / HZ;
+	if (dt <= 0)
+		dt = 1;
+	db = mdev->rs_total;
+	dbdt = Bit2KB(db/dt);
+	mdev->rs_paused /= HZ;
+
+	if (!get_ldev(mdev))
+		goto out;
+
+	spin_lock_irq(&mdev->req_lock);
+	os = mdev->state;
+
+	/* This protects us against multiple calls (that can happen in the presence
+	   of application IO), and against connectivity loss just before we arrive here. */
+	if (os.conn <= C_CONNECTED)
+		goto out_unlock;
+
+	ns = os;
+	ns.conn = C_CONNECTED;
+
+	dev_info(DEV, "%s done (total %lu sec; paused %lu sec; %lu K/sec)\n",
+	     (os.conn == C_VERIFY_S || os.conn == C_VERIFY_T) ?
+	     "Online verify " : "Resync",
+	     dt + mdev->rs_paused, mdev->rs_paused, dbdt);
+
+	n_oos = drbd_bm_total_weight(mdev);
+
+	if (os.conn == C_VERIFY_S || os.conn == C_VERIFY_T) {
+		if (n_oos) {
+			dev_alert(DEV, "Online verify found %lu %dk block out of sync!\n",
+			      n_oos, Bit2KB(1));
+			khelper_cmd = "out-of-sync";
+		}
+	} else {
+		D_ASSERT((n_oos - mdev->rs_failed) == 0);
+
+		if (os.conn == C_SYNC_TARGET || os.conn == C_PAUSED_SYNC_T)
+			khelper_cmd = "after-resync-target";
+
+		if (mdev->csums_tfm && mdev->rs_total) {
+			const unsigned long s = mdev->rs_same_csum;
+			const unsigned long t = mdev->rs_total;
+			const int ratio =
+				(t == 0)     ? 0 :
+			(t < 100000) ? ((s*100)/t) : (s/(t/100));
+			dev_info(DEV, "%u %% had equal check sums, eliminated: %luK; "
+			     "transferred %luK total %luK\n",
+			     ratio,
+			     Bit2KB(mdev->rs_same_csum),
+			     Bit2KB(mdev->rs_total - mdev->rs_same_csum),
+			     Bit2KB(mdev->rs_total));
+		}
+	}
+
+	if (mdev->rs_failed) {
+		dev_info(DEV, "            %lu failed blocks\n", mdev->rs_failed);
+
+		if (os.conn == C_SYNC_TARGET || os.conn == C_PAUSED_SYNC_T) {
+			ns.disk = D_INCONSISTENT;
+			ns.pdsk = D_UP_TO_DATE;
+		} else {
+			ns.disk = D_UP_TO_DATE;
+			ns.pdsk = D_INCONSISTENT;
+		}
+	} else {
+		ns.disk = D_UP_TO_DATE;
+		ns.pdsk = D_UP_TO_DATE;
+
+		if (os.conn == C_SYNC_TARGET || os.conn == C_PAUSED_SYNC_T) {
+			if (mdev->p_uuid) {
+				int i;
+				for (i = UI_BITMAP ; i <= UI_HISTORY_END ; i++)
+					_drbd_uuid_set(mdev, i, mdev->p_uuid[i]);
+				drbd_uuid_set(mdev, UI_BITMAP, mdev->ldev->md.uuid[UI_CURRENT]);
+				_drbd_uuid_set(mdev, UI_CURRENT, mdev->p_uuid[UI_CURRENT]);
+			} else {
+				dev_err(DEV, "mdev->p_uuid is NULL! BUG\n");
+			}
+		}
+
+		drbd_uuid_set_bm(mdev, 0UL);
+
+		if (mdev->p_uuid) {
+			/* Now the two UUID sets are equal, update what we
+			 * know of the peer. */
+			int i;
+			for (i = UI_CURRENT ; i <= UI_HISTORY_END ; i++)
+				mdev->p_uuid[i] = mdev->ldev->md.uuid[i];
+		}
+	}
+
+	_drbd_set_state(mdev, ns, CS_VERBOSE, NULL);
+out_unlock:
+	spin_unlock_irq(&mdev->req_lock);
+	put_ldev(mdev);
+out:
+	mdev->rs_total  = 0;
+	mdev->rs_failed = 0;
+	mdev->rs_paused = 0;
+	mdev->ov_start_sector = 0;
+
+	if (test_and_clear_bit(WRITE_BM_AFTER_RESYNC, &mdev->flags)) {
+		dev_warn(DEV, "Writing the whole bitmap, due to failed kmalloc\n");
+		drbd_queue_bitmap_io(mdev, &drbd_bm_write, NULL, "write from resync_finished");
+	}
+
+	if (khelper_cmd)
+		drbd_khelper(mdev, khelper_cmd);
+
+	return 1;
+}
+
+/* helper */
+static void move_to_net_ee_or_free(struct drbd_conf *mdev, struct drbd_epoch_entry *e)
+{
+	if (drbd_bio_has_active_page(e->private_bio)) {
+		/* This might happen if sendpage() has not finished */
+		spin_lock_irq(&mdev->req_lock);
+		list_add_tail(&e->w.list, &mdev->net_ee);
+		spin_unlock_irq(&mdev->req_lock);
+	} else
+		drbd_free_ee(mdev, e);
+}
+
+/**
+ * w_e_end_data_req() - Worker callback, to send a P_DATA_REPLY packet in response to a P_DATA_REQUEST
+ * @mdev:	DRBD device.
+ * @w:		work object.
+ * @cancel:	The connection will be closed anyways
+ */
+int w_e_end_data_req(struct drbd_conf *mdev, struct drbd_work *w, int cancel)
+{
+	struct drbd_epoch_entry *e = container_of(w, struct drbd_epoch_entry, w);
+	int ok;
+
+	if (unlikely(cancel)) {
+		drbd_free_ee(mdev, e);
+		dec_unacked(mdev);
+		return 1;
+	}
+
+	if (likely(drbd_bio_uptodate(e->private_bio))) {
+		ok = drbd_send_block(mdev, P_DATA_REPLY, e);
+	} else {
+		if (__ratelimit(&drbd_ratelimit_state))
+			dev_err(DEV, "Sending NegDReply. sector=%llus.\n",
+			    (unsigned long long)e->sector);
+
+		ok = drbd_send_ack(mdev, P_NEG_DREPLY, e);
+	}
+
+	dec_unacked(mdev);
+
+	move_to_net_ee_or_free(mdev, e);
+
+	if (unlikely(!ok))
+		dev_err(DEV, "drbd_send_block() failed\n");
+	return ok;
+}
+
+/**
+ * w_e_end_rsdata_req() - Worker callback to send a P_RS_DATA_REPLY packet in response to a P_RS_DATA_REQUESTRS
+ * @mdev:	DRBD device.
+ * @w:		work object.
+ * @cancel:	The connection will be closed anyways
+ */
+int w_e_end_rsdata_req(struct drbd_conf *mdev, struct drbd_work *w, int cancel)
+{
+	struct drbd_epoch_entry *e = container_of(w, struct drbd_epoch_entry, w);
+	int ok;
+
+	if (unlikely(cancel)) {
+		drbd_free_ee(mdev, e);
+		dec_unacked(mdev);
+		return 1;
+	}
+
+	if (get_ldev_if_state(mdev, D_FAILED)) {
+		drbd_rs_complete_io(mdev, e->sector);
+		put_ldev(mdev);
+	}
+
+	if (likely(drbd_bio_uptodate(e->private_bio))) {
+		if (likely(mdev->state.pdsk >= D_INCONSISTENT)) {
+			inc_rs_pending(mdev);
+			ok = drbd_send_block(mdev, P_RS_DATA_REPLY, e);
+		} else {
+			if (__ratelimit(&drbd_ratelimit_state))
+				dev_err(DEV, "Not sending RSDataReply, "
+				    "partner DISKLESS!\n");
+			ok = 1;
+		}
+	} else {
+		if (__ratelimit(&drbd_ratelimit_state))
+			dev_err(DEV, "Sending NegRSDReply. sector %llus.\n",
+			    (unsigned long long)e->sector);
+
+		ok = drbd_send_ack(mdev, P_NEG_RS_DREPLY, e);
+
+		/* update resync data with failure */
+		drbd_rs_failed_io(mdev, e->sector, e->size);
+	}
+
+	dec_unacked(mdev);
+
+	move_to_net_ee_or_free(mdev, e);
+
+	if (unlikely(!ok))
+		dev_err(DEV, "drbd_send_block() failed\n");
+	return ok;
+}
+
+int w_e_end_csum_rs_req(struct drbd_conf *mdev, struct drbd_work *w, int cancel)
+{
+	struct drbd_epoch_entry *e = container_of(w, struct drbd_epoch_entry, w);
+	struct digest_info *di;
+	int digest_size;
+	void *digest = NULL;
+	int ok, eq = 0;
+
+	if (unlikely(cancel)) {
+		drbd_free_ee(mdev, e);
+		dec_unacked(mdev);
+		return 1;
+	}
+
+	drbd_rs_complete_io(mdev, e->sector);
+
+	di = (struct digest_info *)(unsigned long)e->block_id;
+
+	if (likely(drbd_bio_uptodate(e->private_bio))) {
+		/* quick hack to try to avoid a race against reconfiguration.
+		 * a real fix would be much more involved,
+		 * introducing more locking mechanisms */
+		if (mdev->csums_tfm) {
+			digest_size = crypto_hash_digestsize(mdev->csums_tfm);
+			D_ASSERT(digest_size == di->digest_size);
+			digest = kmalloc(digest_size, GFP_NOIO);
+		}
+		if (digest) {
+			drbd_csum(mdev, mdev->csums_tfm, e->private_bio, digest);
+			eq = !memcmp(digest, di->digest, digest_size);
+			kfree(digest);
+		}
+
+		if (eq) {
+			drbd_set_in_sync(mdev, e->sector, e->size);
+			mdev->rs_same_csum++;
+			ok = drbd_send_ack(mdev, P_RS_IS_IN_SYNC, e);
+		} else {
+			inc_rs_pending(mdev);
+			e->block_id = ID_SYNCER;
+			ok = drbd_send_block(mdev, P_RS_DATA_REPLY, e);
+		}
+	} else {
+		ok = drbd_send_ack(mdev, P_NEG_RS_DREPLY, e);
+		if (__ratelimit(&drbd_ratelimit_state))
+			dev_err(DEV, "Sending NegDReply. I guess it gets messy.\n");
+	}
+
+	dec_unacked(mdev);
+
+	kfree(di);
+
+	move_to_net_ee_or_free(mdev, e);
+
+	if (unlikely(!ok))
+		dev_err(DEV, "drbd_send_block/ack() failed\n");
+	return ok;
+}
+
+int w_e_end_ov_req(struct drbd_conf *mdev, struct drbd_work *w, int cancel)
+{
+	struct drbd_epoch_entry *e = container_of(w, struct drbd_epoch_entry, w);
+	int digest_size;
+	void *digest;
+	int ok = 1;
+
+	if (unlikely(cancel))
+		goto out;
+
+	if (unlikely(!drbd_bio_uptodate(e->private_bio)))
+		goto out;
+
+	digest_size = crypto_hash_digestsize(mdev->verify_tfm);
+	/* FIXME if this allocation fails, online verify will not terminate! */
+	digest = kmalloc(digest_size, GFP_NOIO);
+	if (digest) {
+		drbd_csum(mdev, mdev->verify_tfm, e->private_bio, digest);
+		inc_rs_pending(mdev);
+		ok = drbd_send_drequest_csum(mdev, e->sector, e->size,
+					     digest, digest_size, P_OV_REPLY);
+		if (!ok)
+			dec_rs_pending(mdev);
+		kfree(digest);
+	}
+
+out:
+	drbd_free_ee(mdev, e);
+
+	dec_unacked(mdev);
+
+	return ok;
+}
+
+void drbd_ov_oos_found(struct drbd_conf *mdev, sector_t sector, int size)
+{
+	if (mdev->ov_last_oos_start + mdev->ov_last_oos_size == sector) {
+		mdev->ov_last_oos_size += size>>9;
+	} else {
+		mdev->ov_last_oos_start = sector;
+		mdev->ov_last_oos_size = size>>9;
+	}
+	drbd_set_out_of_sync(mdev, sector, size);
+	set_bit(WRITE_BM_AFTER_RESYNC, &mdev->flags);
+}
+
+int w_e_end_ov_reply(struct drbd_conf *mdev, struct drbd_work *w, int cancel)
+{
+	struct drbd_epoch_entry *e = container_of(w, struct drbd_epoch_entry, w);
+	struct digest_info *di;
+	int digest_size;
+	void *digest;
+	int ok, eq = 0;
+
+	if (unlikely(cancel)) {
+		drbd_free_ee(mdev, e);
+		dec_unacked(mdev);
+		return 1;
+	}
+
+	/* after "cancel", because after drbd_disconnect/drbd_rs_cancel_all
+	 * the resync lru has been cleaned up already */
+	drbd_rs_complete_io(mdev, e->sector);
+
+	di = (struct digest_info *)(unsigned long)e->block_id;
+
+	if (likely(drbd_bio_uptodate(e->private_bio))) {
+		digest_size = crypto_hash_digestsize(mdev->verify_tfm);
+		digest = kmalloc(digest_size, GFP_NOIO);
+		if (digest) {
+			drbd_csum(mdev, mdev->verify_tfm, e->private_bio, digest);
+
+			D_ASSERT(digest_size == di->digest_size);
+			eq = !memcmp(digest, di->digest, digest_size);
+			kfree(digest);
+		}
+	} else {
+		ok = drbd_send_ack(mdev, P_NEG_RS_DREPLY, e);
+		if (__ratelimit(&drbd_ratelimit_state))
+			dev_err(DEV, "Sending NegDReply. I guess it gets messy.\n");
+	}
+
+	dec_unacked(mdev);
+
+	kfree(di);
+
+	if (!eq)
+		drbd_ov_oos_found(mdev, e->sector, e->size);
+	else
+		ov_oos_print(mdev);
+
+	ok = drbd_send_ack_ex(mdev, P_OV_RESULT, e->sector, e->size,
+			      eq ? ID_IN_SYNC : ID_OUT_OF_SYNC);
+
+	drbd_free_ee(mdev, e);
+
+	if (--mdev->ov_left == 0) {
+		ov_oos_print(mdev);
+		drbd_resync_finished(mdev);
+	}
+
+	return ok;
+}
+
+int w_prev_work_done(struct drbd_conf *mdev, struct drbd_work *w, int cancel)
+{
+	struct drbd_wq_barrier *b = container_of(w, struct drbd_wq_barrier, w);
+	complete(&b->done);
+	return 1;
+}
+
+int w_send_barrier(struct drbd_conf *mdev, struct drbd_work *w, int cancel)
+{
+	struct drbd_tl_epoch *b = container_of(w, struct drbd_tl_epoch, w);
+	struct p_barrier *p = &mdev->data.sbuf.barrier;
+	int ok = 1;
+
+	/* really avoid racing with tl_clear.  w.cb may have been referenced
+	 * just before it was reassigned and re-queued, so double check that.
+	 * actually, this race was harmless, since we only try to send the
+	 * barrier packet here, and otherwise do nothing with the object.
+	 * but compare with the head of w_clear_epoch */
+	spin_lock_irq(&mdev->req_lock);
+	if (w->cb != w_send_barrier || mdev->state.conn < C_CONNECTED)
+		cancel = 1;
+	spin_unlock_irq(&mdev->req_lock);
+	if (cancel)
+		return 1;
+
+	if (!drbd_get_data_sock(mdev))
+		return 0;
+	p->barrier = b->br_number;
+	/* inc_ap_pending was done where this was queued.
+	 * dec_ap_pending will be done in got_BarrierAck
+	 * or (on connection loss) in w_clear_epoch.  */
+	ok = _drbd_send_cmd(mdev, mdev->data.socket, P_BARRIER,
+				(struct p_header *)p, sizeof(*p), 0);
+	drbd_put_data_sock(mdev);
+
+	return ok;
+}
+
+int w_send_write_hint(struct drbd_conf *mdev, struct drbd_work *w, int cancel)
+{
+	if (cancel)
+		return 1;
+	return drbd_send_short_cmd(mdev, P_UNPLUG_REMOTE);
+}
+
+/**
+ * w_send_dblock() - Worker callback to send a P_DATA packet in order to mirror a write request
+ * @mdev:	DRBD device.
+ * @w:		work object.
+ * @cancel:	The connection will be closed anyways
+ */
+int w_send_dblock(struct drbd_conf *mdev, struct drbd_work *w, int cancel)
+{
+	struct drbd_request *req = container_of(w, struct drbd_request, w);
+	int ok;
+
+	if (unlikely(cancel)) {
+		req_mod(req, send_canceled);
+		return 1;
+	}
+
+	ok = drbd_send_dblock(mdev, req);
+	req_mod(req, ok ? handed_over_to_network : send_failed);
+
+	return ok;
+}
+
+/**
+ * w_send_read_req() - Worker callback to send a read request (P_DATA_REQUEST) packet
+ * @mdev:	DRBD device.
+ * @w:		work object.
+ * @cancel:	The connection will be closed anyways
+ */
+int w_send_read_req(struct drbd_conf *mdev, struct drbd_work *w, int cancel)
+{
+	struct drbd_request *req = container_of(w, struct drbd_request, w);
+	int ok;
+
+	if (unlikely(cancel)) {
+		req_mod(req, send_canceled);
+		return 1;
+	}
+
+	ok = drbd_send_drequest(mdev, P_DATA_REQUEST, req->sector, req->size,
+				(unsigned long)req);
+
+	if (!ok) {
+		/* ?? we set C_TIMEOUT or C_BROKEN_PIPE in drbd_send();
+		 * so this is probably redundant */
+		if (mdev->state.conn >= C_CONNECTED)
+			drbd_force_state(mdev, NS(conn, C_NETWORK_FAILURE));
+	}
+	req_mod(req, ok ? handed_over_to_network : send_failed);
+
+	return ok;
+}
+
+static int _drbd_may_sync_now(struct drbd_conf *mdev)
+{
+	struct drbd_conf *odev = mdev;
+
+	while (1) {
+		if (odev->sync_conf.after == -1)
+			return 1;
+		odev = minor_to_mdev(odev->sync_conf.after);
+		ERR_IF(!odev) return 1;
+		if ((odev->state.conn >= C_SYNC_SOURCE &&
+		     odev->state.conn <= C_PAUSED_SYNC_T) ||
+		    odev->state.aftr_isp || odev->state.peer_isp ||
+		    odev->state.user_isp)
+			return 0;
+	}
+}
+
+/**
+ * _drbd_pause_after() - Pause resync on all devices that may not resync now
+ * @mdev:	DRBD device.
+ *
+ * Called from process context only (admin command and after_state_ch).
+ */
+static int _drbd_pause_after(struct drbd_conf *mdev)
+{
+	struct drbd_conf *odev;
+	int i, rv = 0;
+
+	for (i = 0; i < minor_count; i++) {
+		odev = minor_to_mdev(i);
+		if (!odev)
+			continue;
+		if (odev->state.conn == C_STANDALONE && odev->state.disk == D_DISKLESS)
+			continue;
+		if (!_drbd_may_sync_now(odev))
+			rv |= (__drbd_set_state(_NS(odev, aftr_isp, 1), CS_HARD, NULL)
+			       != SS_NOTHING_TO_DO);
+	}
+
+	return rv;
+}
+
+/**
+ * _drbd_resume_next() - Resume resync on all devices that may resync now
+ * @mdev:	DRBD device.
+ *
+ * Called from process context only (admin command and worker).
+ */
+static int _drbd_resume_next(struct drbd_conf *mdev)
+{
+	struct drbd_conf *odev;
+	int i, rv = 0;
+
+	for (i = 0; i < minor_count; i++) {
+		odev = minor_to_mdev(i);
+		if (!odev)
+			continue;
+		if (odev->state.conn == C_STANDALONE && odev->state.disk == D_DISKLESS)
+			continue;
+		if (odev->state.aftr_isp) {
+			if (_drbd_may_sync_now(odev))
+				rv |= (__drbd_set_state(_NS(odev, aftr_isp, 0),
+							CS_HARD, NULL)
+				       != SS_NOTHING_TO_DO) ;
+		}
+	}
+	return rv;
+}
+
+void resume_next_sg(struct drbd_conf *mdev)
+{
+	write_lock_irq(&global_state_lock);
+	_drbd_resume_next(mdev);
+	write_unlock_irq(&global_state_lock);
+}
+
+void suspend_other_sg(struct drbd_conf *mdev)
+{
+	write_lock_irq(&global_state_lock);
+	_drbd_pause_after(mdev);
+	write_unlock_irq(&global_state_lock);
+}
+
+static int sync_after_error(struct drbd_conf *mdev, int o_minor)
+{
+	struct drbd_conf *odev;
+
+	if (o_minor == -1)
+		return NO_ERROR;
+	if (o_minor < -1 || minor_to_mdev(o_minor) == NULL)
+		return ERR_SYNC_AFTER;
+
+	/* check for loops */
+	odev = minor_to_mdev(o_minor);
+	while (1) {
+		if (odev == mdev)
+			return ERR_SYNC_AFTER_CYCLE;
+
+		/* dependency chain ends here, no cycles. */
+		if (odev->sync_conf.after == -1)
+			return NO_ERROR;
+
+		/* follow the dependency chain */
+		odev = minor_to_mdev(odev->sync_conf.after);
+	}
+}
+
+int drbd_alter_sa(struct drbd_conf *mdev, int na)
+{
+	int changes;
+	int retcode;
+
+	write_lock_irq(&global_state_lock);
+	retcode = sync_after_error(mdev, na);
+	if (retcode == NO_ERROR) {
+		mdev->sync_conf.after = na;
+		do {
+			changes  = _drbd_pause_after(mdev);
+			changes |= _drbd_resume_next(mdev);
+		} while (changes);
+	}
+	write_unlock_irq(&global_state_lock);
+	return retcode;
+}
+
+/**
+ * drbd_start_resync() - Start the resync process
+ * @mdev:	DRBD device.
+ * @side:	Either C_SYNC_SOURCE or C_SYNC_TARGET
+ *
+ * This function might bring you directly into one of the
+ * C_PAUSED_SYNC_* states.
+ */
+void drbd_start_resync(struct drbd_conf *mdev, enum drbd_conns side)
+{
+	union drbd_state ns;
+	int r;
+
+	if (mdev->state.conn >= C_SYNC_SOURCE) {
+		dev_err(DEV, "Resync already running!\n");
+		return;
+	}
+
+	trace_drbd_resync(mdev, TRACE_LVL_SUMMARY, "Resync starting: side=%s\n",
+			  side == C_SYNC_TARGET ? "SyncTarget" : "SyncSource");
+
+	/* In case a previous resync run was aborted by an IO error/detach on the peer. */
+	drbd_rs_cancel_all(mdev);
+
+	if (side == C_SYNC_TARGET) {
+		/* Since application IO was locked out during C_WF_BITMAP_T and
+		   C_WF_SYNC_UUID we are still unmodified. Before going to C_SYNC_TARGET
+		   we check that we might make the data inconsistent. */
+		r = drbd_khelper(mdev, "before-resync-target");
+		r = (r >> 8) & 0xff;
+		if (r > 0) {
+			dev_info(DEV, "before-resync-target handler returned %d, "
+			     "dropping connection.\n", r);
+			drbd_force_state(mdev, NS(conn, C_DISCONNECTING));
+			return;
+		}
+	}
+
+	drbd_state_lock(mdev);
+
+	if (!get_ldev_if_state(mdev, D_NEGOTIATING)) {
+		drbd_state_unlock(mdev);
+		return;
+	}
+
+	if (side == C_SYNC_TARGET) {
+		mdev->bm_resync_fo = 0;
+	} else /* side == C_SYNC_SOURCE */ {
+		u64 uuid;
+
+		get_random_bytes(&uuid, sizeof(u64));
+		drbd_uuid_set(mdev, UI_BITMAP, uuid);
+		drbd_send_sync_uuid(mdev, uuid);
+
+		D_ASSERT(mdev->state.disk == D_UP_TO_DATE);
+	}
+
+	write_lock_irq(&global_state_lock);
+	ns = mdev->state;
+
+	ns.aftr_isp = !_drbd_may_sync_now(mdev);
+
+	ns.conn = side;
+
+	if (side == C_SYNC_TARGET)
+		ns.disk = D_INCONSISTENT;
+	else /* side == C_SYNC_SOURCE */
+		ns.pdsk = D_INCONSISTENT;
+
+	r = __drbd_set_state(mdev, ns, CS_VERBOSE, NULL);
+	ns = mdev->state;
+
+	if (ns.conn < C_CONNECTED)
+		r = SS_UNKNOWN_ERROR;
+
+	if (r == SS_SUCCESS) {
+		mdev->rs_total     =
+		mdev->rs_mark_left = drbd_bm_total_weight(mdev);
+		mdev->rs_failed    = 0;
+		mdev->rs_paused    = 0;
+		mdev->rs_start     =
+		mdev->rs_mark_time = jiffies;
+		mdev->rs_same_csum = 0;
+		_drbd_pause_after(mdev);
+	}
+	write_unlock_irq(&global_state_lock);
+	drbd_state_unlock(mdev);
+	put_ldev(mdev);
+
+	if (r == SS_SUCCESS) {
+		dev_info(DEV, "Began resync as %s (will sync %lu KB [%lu bits set]).\n",
+		     drbd_conn_str(ns.conn),
+		     (unsigned long) mdev->rs_total << (BM_BLOCK_SHIFT-10),
+		     (unsigned long) mdev->rs_total);
+
+		if (mdev->rs_total == 0) {
+			/* Peer still reachable? Beware of failing before-resync-target handlers! */
+			request_ping(mdev);
+			__set_current_state(TASK_INTERRUPTIBLE);
+			schedule_timeout(mdev->net_conf->ping_timeo*HZ/9); /* 9 instead 10 */
+			drbd_resync_finished(mdev);
+			return;
+		}
+
+		/* ns.conn may already be != mdev->state.conn,
+		 * we may have been paused in between, or become paused until
+		 * the timer triggers.
+		 * No matter, that is handled in resync_timer_fn() */
+		if (ns.conn == C_SYNC_TARGET)
+			mod_timer(&mdev->resync_timer, jiffies);
+
+		drbd_md_sync(mdev);
+	}
+}
+
+int drbd_worker(struct drbd_thread *thi)
+{
+	struct drbd_conf *mdev = thi->mdev;
+	struct drbd_work *w = NULL;
+	LIST_HEAD(work_list);
+	int intr = 0, i;
+
+	sprintf(current->comm, "drbd%d_worker", mdev_to_minor(mdev));
+
+	while (get_t_state(thi) == Running) {
+		drbd_thread_current_set_cpu(mdev);
+
+		if (down_trylock(&mdev->data.work.s)) {
+			mutex_lock(&mdev->data.mutex);
+			if (mdev->data.socket && !mdev->net_conf->no_cork)
+				drbd_tcp_uncork(mdev->data.socket);
+			mutex_unlock(&mdev->data.mutex);
+
+			intr = down_interruptible(&mdev->data.work.s);
+
+			mutex_lock(&mdev->data.mutex);
+			if (mdev->data.socket  && !mdev->net_conf->no_cork)
+				drbd_tcp_cork(mdev->data.socket);
+			mutex_unlock(&mdev->data.mutex);
+		}
+
+		if (intr) {
+			D_ASSERT(intr == -EINTR);
+			flush_signals(current);
+			ERR_IF (get_t_state(thi) == Running)
+				continue;
+			break;
+		}
+
+		if (get_t_state(thi) != Running)
+			break;
+		/* With this break, we have done a down() but not consumed
+		   the entry from the list. The cleanup code takes care of
+		   this...   */
+
+		w = NULL;
+		spin_lock_irq(&mdev->data.work.q_lock);
+		ERR_IF(list_empty(&mdev->data.work.q)) {
+			/* something terribly wrong in our logic.
+			 * we were able to down() the semaphore,
+			 * but the list is empty... doh.
+			 *
+			 * what is the best thing to do now?
+			 * try again from scratch, restarting the receiver,
+			 * asender, whatnot? could break even more ugly,
+			 * e.g. when we are primary, but no good local data.
+			 *
+			 * I'll try to get away just starting over this loop.
+			 */
+			spin_unlock_irq(&mdev->data.work.q_lock);
+			continue;
+		}
+		w = list_entry(mdev->data.work.q.next, struct drbd_work, list);
+		list_del_init(&w->list);
+		spin_unlock_irq(&mdev->data.work.q_lock);
+
+		if (!w->cb(mdev, w, mdev->state.conn < C_CONNECTED)) {
+			/* dev_warn(DEV, "worker: a callback failed! \n"); */
+			if (mdev->state.conn >= C_CONNECTED)
+				drbd_force_state(mdev,
+						NS(conn, C_NETWORK_FAILURE));
+		}
+	}
+	D_ASSERT(test_bit(DEVICE_DYING, &mdev->flags));
+	D_ASSERT(test_bit(CONFIG_PENDING, &mdev->flags));
+
+	spin_lock_irq(&mdev->data.work.q_lock);
+	i = 0;
+	while (!list_empty(&mdev->data.work.q)) {
+		list_splice_init(&mdev->data.work.q, &work_list);
+		spin_unlock_irq(&mdev->data.work.q_lock);
+
+		while (!list_empty(&work_list)) {
+			w = list_entry(work_list.next, struct drbd_work, list);
+			list_del_init(&w->list);
+			w->cb(mdev, w, 1);
+			i++; /* dead debugging code */
+		}
+
+		spin_lock_irq(&mdev->data.work.q_lock);
+	}
+	sema_init(&mdev->data.work.s, 0);
+	/* DANGEROUS race: if someone did queue his work within the spinlock,
+	 * but up() ed outside the spinlock, we could get an up() on the
+	 * semaphore without corresponding list entry.
+	 * So don't do that.
+	 */
+	spin_unlock_irq(&mdev->data.work.q_lock);
+
+	D_ASSERT(mdev->state.disk == D_DISKLESS && mdev->state.conn == C_STANDALONE);
+	/* _drbd_set_state only uses stop_nowait.
+	 * wait here for the Exiting receiver. */
+	drbd_thread_stop(&mdev->receiver);
+	drbd_mdev_cleanup(mdev);
+
+	dev_info(DEV, "worker terminated\n");
+
+	clear_bit(DEVICE_DYING, &mdev->flags);
+	clear_bit(CONFIG_PENDING, &mdev->flags);
+	wake_up(&mdev->state_wait);
+
+	return 0;
+}
diff --git a/drivers/block/drbd/drbd_wrappers.h b/drivers/block/drbd/drbd_wrappers.h
new file mode 100644
index 00000000000..f93fa111ce5
--- /dev/null
+++ b/drivers/block/drbd/drbd_wrappers.h
@@ -0,0 +1,91 @@
+#ifndef _DRBD_WRAPPERS_H
+#define _DRBD_WRAPPERS_H
+
+#include <linux/ctype.h>
+#include <linux/mm.h>
+
+/* see get_sb_bdev and bd_claim */
+extern char *drbd_sec_holder;
+
+/* sets the number of 512 byte sectors of our virtual device */
+static inline void drbd_set_my_capacity(struct drbd_conf *mdev,
+					sector_t size)
+{
+	/* set_capacity(mdev->this_bdev->bd_disk, size); */
+	set_capacity(mdev->vdisk, size);
+	mdev->this_bdev->bd_inode->i_size = (loff_t)size << 9;
+}
+
+#define drbd_bio_uptodate(bio) bio_flagged(bio, BIO_UPTODATE)
+
+static inline int drbd_bio_has_active_page(struct bio *bio)
+{
+	struct bio_vec *bvec;
+	int i;
+
+	__bio_for_each_segment(bvec, bio, i, 0) {
+		if (page_count(bvec->bv_page) > 1)
+			return 1;
+	}
+
+	return 0;
+}
+
+/* bi_end_io handlers */
+extern void drbd_md_io_complete(struct bio *bio, int error);
+extern void drbd_endio_read_sec(struct bio *bio, int error);
+extern void drbd_endio_write_sec(struct bio *bio, int error);
+extern void drbd_endio_pri(struct bio *bio, int error);
+
+/*
+ * used to submit our private bio
+ */
+static inline void drbd_generic_make_request(struct drbd_conf *mdev,
+					     int fault_type, struct bio *bio)
+{
+	__release(local);
+	if (!bio->bi_bdev) {
+		printk(KERN_ERR "drbd%d: drbd_generic_make_request: "
+				"bio->bi_bdev == NULL\n",
+		       mdev_to_minor(mdev));
+		dump_stack();
+		bio_endio(bio, -ENODEV);
+		return;
+	}
+
+	if (FAULT_ACTIVE(mdev, fault_type))
+		bio_endio(bio, -EIO);
+	else
+		generic_make_request(bio);
+}
+
+static inline void drbd_plug_device(struct drbd_conf *mdev)
+{
+	struct request_queue *q;
+	q = bdev_get_queue(mdev->this_bdev);
+
+	spin_lock_irq(q->queue_lock);
+
+/* XXX the check on !blk_queue_plugged is redundant,
+ * implicitly checked in blk_plug_device */
+
+	if (!blk_queue_plugged(q)) {
+		blk_plug_device(q);
+		del_timer(&q->unplug_timer);
+		/* unplugging should not happen automatically... */
+	}
+	spin_unlock_irq(q->queue_lock);
+}
+
+static inline int drbd_crypto_is_hash(struct crypto_tfm *tfm)
+{
+        return (crypto_tfm_alg_type(tfm) & CRYPTO_ALG_TYPE_HASH_MASK)
+                == CRYPTO_ALG_TYPE_HASH;
+}
+
+#ifndef __CHECKER__
+# undef __cond_lock
+# define __cond_lock(x,c) (c)
+#endif
+
+#endif