[PATCH] OCFS2: The Second Oracle Cluster Filesystem

A distributed lock manager built with the cluster file system use case
in mind. The OCFS2 dlm exposes a VMS style API, though things have
been simplified internally. The only lock levels implemented currently
are NLMODE, PRMODE and EXMODE.

Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>
Signed-off-by: Kurt Hackel <kurt.hackel@oracle.com>

1 files changed, 2666 insertions, 0 deletions

diff --git a/fs/ocfs2/dlm/dlmmaster.c b/fs/ocfs2/dlm/dlmmaster.c
new file mode 100644
index 00000000000..047279546b4
--- /dev/null
+++ b/fs/ocfs2/dlm/dlmmaster.c
@@ -0,0 +1,2666 @@
+/* -*- mode: c; c-basic-offset: 8; -*-
+ * vim: noexpandtab sw=8 ts=8 sts=0:
+ *
+ * dlmmod.c
+ *
+ * standalone DLM module
+ *
+ * Copyright (C) 2004 Oracle.  All rights reserved.
+ *
+ * This program 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 of the License, or (at your option) any later version.
+ *
+ * This program 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 this program; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 021110-1307, USA.
+ *
+ */
+
+
+#include <linux/module.h>
+#include <linux/fs.h>
+#include <linux/types.h>
+#include <linux/slab.h>
+#include <linux/highmem.h>
+#include <linux/utsname.h>
+#include <linux/init.h>
+#include <linux/sysctl.h>
+#include <linux/random.h>
+#include <linux/blkdev.h>
+#include <linux/socket.h>
+#include <linux/inet.h>
+#include <linux/spinlock.h>
+#include <linux/delay.h>
+
+
+#include "cluster/heartbeat.h"
+#include "cluster/nodemanager.h"
+#include "cluster/tcp.h"
+
+#include "dlmapi.h"
+#include "dlmcommon.h"
+#include "dlmdebug.h"
+
+#define MLOG_MASK_PREFIX (ML_DLM|ML_DLM_MASTER)
+#include "cluster/masklog.h"
+
+enum dlm_mle_type {
+	DLM_MLE_BLOCK,
+	DLM_MLE_MASTER,
+	DLM_MLE_MIGRATION
+};
+
+struct dlm_lock_name
+{
+	u8 len;
+	u8 name[DLM_LOCKID_NAME_MAX];
+};
+
+struct dlm_master_list_entry
+{
+	struct list_head list;
+	struct list_head hb_events;
+	struct dlm_ctxt *dlm;
+	spinlock_t spinlock;
+	wait_queue_head_t wq;
+	atomic_t woken;
+	struct kref mle_refs;
+	unsigned long maybe_map[BITS_TO_LONGS(O2NM_MAX_NODES)];
+	unsigned long vote_map[BITS_TO_LONGS(O2NM_MAX_NODES)];
+	unsigned long response_map[BITS_TO_LONGS(O2NM_MAX_NODES)];
+	unsigned long node_map[BITS_TO_LONGS(O2NM_MAX_NODES)];
+	u8 master;
+	u8 new_master;
+	enum dlm_mle_type type;
+	struct o2hb_callback_func mle_hb_up;
+	struct o2hb_callback_func mle_hb_down;
+	union {
+		struct dlm_lock_resource *res;
+		struct dlm_lock_name name;
+	} u;
+};
+
+static void dlm_mle_node_down(struct dlm_ctxt *dlm,
+			      struct dlm_master_list_entry *mle,
+			      struct o2nm_node *node,
+			      int idx);
+static void dlm_mle_node_up(struct dlm_ctxt *dlm,
+			    struct dlm_master_list_entry *mle,
+			    struct o2nm_node *node,
+			    int idx);
+
+static void dlm_assert_master_worker(struct dlm_work_item *item, void *data);
+static int dlm_do_assert_master(struct dlm_ctxt *dlm, const char *lockname,
+				unsigned int namelen, void *nodemap,
+				u32 flags);
+
+static inline int dlm_mle_equal(struct dlm_ctxt *dlm,
+				struct dlm_master_list_entry *mle,
+				const char *name,
+				unsigned int namelen)
+{
+	struct dlm_lock_resource *res;
+
+	if (dlm != mle->dlm)
+		return 0;
+
+	if (mle->type == DLM_MLE_BLOCK ||
+	    mle->type == DLM_MLE_MIGRATION) {
+		if (namelen != mle->u.name.len ||
+    	    	    memcmp(name, mle->u.name.name, namelen)!=0)
+			return 0;
+	} else {
+		res = mle->u.res;
+		if (namelen != res->lockname.len ||
+		    memcmp(res->lockname.name, name, namelen) != 0)
+			return 0;
+	}
+	return 1;
+}
+
+#if 0
+/* Code here is included but defined out as it aids debugging */
+
+void dlm_print_one_mle(struct dlm_master_list_entry *mle)
+{
+	int i = 0, refs;
+	char *type;
+	char attached;
+	u8 master;
+	unsigned int namelen;
+	const char *name;
+	struct kref *k;
+
+	k = &mle->mle_refs;
+	if (mle->type == DLM_MLE_BLOCK)
+		type = "BLK";
+	else if (mle->type == DLM_MLE_MASTER)
+		type = "MAS";
+	else
+		type = "MIG";
+	refs = atomic_read(&k->refcount);
+	master = mle->master;
+	attached = (list_empty(&mle->hb_events) ? 'N' : 'Y');
+
+	if (mle->type != DLM_MLE_MASTER) {
+		namelen = mle->u.name.len;
+		name = mle->u.name.name;
+	} else {
+		namelen = mle->u.res->lockname.len;
+		name = mle->u.res->lockname.name;
+	}
+
+	mlog(ML_NOTICE, "  #%3d: %3s  %3d  %3u   %3u %c    (%d)%.*s\n",
+		  i, type, refs, master, mle->new_master, attached,
+		  namelen, namelen, name);
+}
+
+static void dlm_dump_mles(struct dlm_ctxt *dlm)
+{
+	struct dlm_master_list_entry *mle;
+	struct list_head *iter;
+	
+	mlog(ML_NOTICE, "dumping all mles for domain %s:\n", dlm->name);
+	mlog(ML_NOTICE, "  ####: type refs owner new events? lockname nodemap votemap respmap maybemap\n");
+	spin_lock(&dlm->master_lock);
+	list_for_each(iter, &dlm->master_list) {
+		mle = list_entry(iter, struct dlm_master_list_entry, list);
+		dlm_print_one_mle(mle);
+	}
+	spin_unlock(&dlm->master_lock);
+}
+
+extern spinlock_t dlm_domain_lock;
+extern struct list_head dlm_domains;
+
+int dlm_dump_all_mles(const char __user *data, unsigned int len)
+{
+	struct list_head *iter;
+	struct dlm_ctxt *dlm;
+
+	spin_lock(&dlm_domain_lock);
+	list_for_each(iter, &dlm_domains) {
+		dlm = list_entry (iter, struct dlm_ctxt, list);
+		mlog(ML_NOTICE, "found dlm: %p, name=%s\n", dlm, dlm->name);
+		dlm_dump_mles(dlm);
+	}
+	spin_unlock(&dlm_domain_lock);
+	return len;
+}
+EXPORT_SYMBOL_GPL(dlm_dump_all_mles);
+
+#endif  /*  0  */
+
+
+static kmem_cache_t *dlm_mle_cache = NULL;
+
+
+static void dlm_mle_release(struct kref *kref);
+static void dlm_init_mle(struct dlm_master_list_entry *mle,
+			enum dlm_mle_type type,
+			struct dlm_ctxt *dlm,
+			struct dlm_lock_resource *res,
+			const char *name,
+			unsigned int namelen);
+static void dlm_put_mle(struct dlm_master_list_entry *mle);
+static void __dlm_put_mle(struct dlm_master_list_entry *mle);
+static int dlm_find_mle(struct dlm_ctxt *dlm,
+			struct dlm_master_list_entry **mle,
+			char *name, unsigned int namelen);
+
+static int dlm_do_master_request(struct dlm_master_list_entry *mle, int to);
+
+
+static int dlm_wait_for_lock_mastery(struct dlm_ctxt *dlm,
+				     struct dlm_lock_resource *res,
+				     struct dlm_master_list_entry *mle,
+				     int *blocked);
+static int dlm_restart_lock_mastery(struct dlm_ctxt *dlm,
+				    struct dlm_lock_resource *res,
+				    struct dlm_master_list_entry *mle,
+				    int blocked);
+static int dlm_add_migration_mle(struct dlm_ctxt *dlm,
+				 struct dlm_lock_resource *res,
+				 struct dlm_master_list_entry *mle,
+				 struct dlm_master_list_entry **oldmle,
+				 const char *name, unsigned int namelen,
+				 u8 new_master, u8 master);
+
+static u8 dlm_pick_migration_target(struct dlm_ctxt *dlm,
+				    struct dlm_lock_resource *res);
+static void dlm_remove_nonlocal_locks(struct dlm_ctxt *dlm,
+				      struct dlm_lock_resource *res);
+static int dlm_mark_lockres_migrating(struct dlm_ctxt *dlm,
+				       struct dlm_lock_resource *res,
+				       u8 target);
+
+
+int dlm_is_host_down(int errno)
+{
+	switch (errno) {
+		case -EBADF:
+		case -ECONNREFUSED:
+		case -ENOTCONN:
+		case -ECONNRESET:
+		case -EPIPE:
+		case -EHOSTDOWN:
+		case -EHOSTUNREACH:
+		case -ETIMEDOUT:
+		case -ECONNABORTED:
+		case -ENETDOWN:
+		case -ENETUNREACH:
+		case -ENETRESET:
+		case -ESHUTDOWN:
+		case -ENOPROTOOPT:
+		case -EINVAL:   /* if returned from our tcp code,
+				   this means there is no socket */
+			return 1;
+	}
+	return 0;
+}
+
+
+/*
+ * MASTER LIST FUNCTIONS
+ */
+
+
+/*
+ * regarding master list entries and heartbeat callbacks:
+ *
+ * in order to avoid sleeping and allocation that occurs in
+ * heartbeat, master list entries are simply attached to the
+ * dlm's established heartbeat callbacks.  the mle is attached
+ * when it is created, and since the dlm->spinlock is held at
+ * that time, any heartbeat event will be properly discovered
+ * by the mle.  the mle needs to be detached from the
+ * dlm->mle_hb_events list as soon as heartbeat events are no
+ * longer useful to the mle, and before the mle is freed.
+ *
+ * as a general rule, heartbeat events are no longer needed by
+ * the mle once an "answer" regarding the lock master has been
+ * received.
+ */
+static inline void __dlm_mle_attach_hb_events(struct dlm_ctxt *dlm,
+					      struct dlm_master_list_entry *mle)
+{
+	assert_spin_locked(&dlm->spinlock);
+
+	list_add_tail(&mle->hb_events, &dlm->mle_hb_events);
+}
+
+
+static inline void __dlm_mle_detach_hb_events(struct dlm_ctxt *dlm,
+					      struct dlm_master_list_entry *mle)
+{
+	if (!list_empty(&mle->hb_events))
+		list_del_init(&mle->hb_events);
+}
+
+
+static inline void dlm_mle_detach_hb_events(struct dlm_ctxt *dlm,
+					    struct dlm_master_list_entry *mle)
+{
+	spin_lock(&dlm->spinlock);
+	__dlm_mle_detach_hb_events(dlm, mle);
+	spin_unlock(&dlm->spinlock);
+}
+
+/* remove from list and free */
+static void __dlm_put_mle(struct dlm_master_list_entry *mle)
+{
+	struct dlm_ctxt *dlm;
+	dlm = mle->dlm;
+
+	assert_spin_locked(&dlm->spinlock);
+	assert_spin_locked(&dlm->master_lock);
+	BUG_ON(!atomic_read(&mle->mle_refs.refcount));
+
+	kref_put(&mle->mle_refs, dlm_mle_release);
+}
+
+
+/* must not have any spinlocks coming in */
+static void dlm_put_mle(struct dlm_master_list_entry *mle)
+{
+	struct dlm_ctxt *dlm;
+	dlm = mle->dlm;
+
+	spin_lock(&dlm->spinlock);
+	spin_lock(&dlm->master_lock);
+	__dlm_put_mle(mle);
+	spin_unlock(&dlm->master_lock);
+	spin_unlock(&dlm->spinlock);
+}
+
+static inline void dlm_get_mle(struct dlm_master_list_entry *mle)
+{
+	kref_get(&mle->mle_refs);
+}
+
+static void dlm_init_mle(struct dlm_master_list_entry *mle,
+			enum dlm_mle_type type,
+			struct dlm_ctxt *dlm,
+			struct dlm_lock_resource *res,
+			const char *name,
+			unsigned int namelen)
+{
+	assert_spin_locked(&dlm->spinlock);
+
+	mle->dlm = dlm;
+	mle->type = type;
+	INIT_LIST_HEAD(&mle->list);
+	INIT_LIST_HEAD(&mle->hb_events);
+	memset(mle->maybe_map, 0, sizeof(mle->maybe_map));
+	spin_lock_init(&mle->spinlock);
+	init_waitqueue_head(&mle->wq);
+	atomic_set(&mle->woken, 0);
+	kref_init(&mle->mle_refs);
+	memset(mle->response_map, 0, sizeof(mle->response_map));
+	mle->master = O2NM_MAX_NODES;
+	mle->new_master = O2NM_MAX_NODES;
+
+	if (mle->type == DLM_MLE_MASTER) {
+		BUG_ON(!res);
+		mle->u.res = res;
+	} else if (mle->type == DLM_MLE_BLOCK) {
+		BUG_ON(!name);
+		memcpy(mle->u.name.name, name, namelen);
+		mle->u.name.len = namelen;
+	} else /* DLM_MLE_MIGRATION */ {
+		BUG_ON(!name);
+		memcpy(mle->u.name.name, name, namelen);
+		mle->u.name.len = namelen;
+	}
+
+	/* copy off the node_map and register hb callbacks on our copy */
+	memcpy(mle->node_map, dlm->domain_map, sizeof(mle->node_map));
+	memcpy(mle->vote_map, dlm->domain_map, sizeof(mle->vote_map));
+	clear_bit(dlm->node_num, mle->vote_map);
+	clear_bit(dlm->node_num, mle->node_map);
+
+	/* attach the mle to the domain node up/down events */
+	__dlm_mle_attach_hb_events(dlm, mle);
+}
+
+
+/* returns 1 if found, 0 if not */
+static int dlm_find_mle(struct dlm_ctxt *dlm,
+			struct dlm_master_list_entry **mle,
+			char *name, unsigned int namelen)
+{
+	struct dlm_master_list_entry *tmpmle;
+	struct list_head *iter;
+
+	assert_spin_locked(&dlm->master_lock);
+
+	list_for_each(iter, &dlm->master_list) {
+		tmpmle = list_entry(iter, struct dlm_master_list_entry, list);
+		if (!dlm_mle_equal(dlm, tmpmle, name, namelen))
+			continue;
+		dlm_get_mle(tmpmle);
+		*mle = tmpmle;
+		return 1;
+	}
+	return 0;
+}
+
+void dlm_hb_event_notify_attached(struct dlm_ctxt *dlm, int idx, int node_up)
+{
+	struct dlm_master_list_entry *mle;
+	struct list_head *iter;
+
+	assert_spin_locked(&dlm->spinlock);
+	
+	list_for_each(iter, &dlm->mle_hb_events) {
+		mle = list_entry(iter, struct dlm_master_list_entry, 
+				 hb_events);
+		if (node_up)
+			dlm_mle_node_up(dlm, mle, NULL, idx);
+		else
+			dlm_mle_node_down(dlm, mle, NULL, idx);
+	}
+}
+
+static void dlm_mle_node_down(struct dlm_ctxt *dlm,
+			      struct dlm_master_list_entry *mle,
+			      struct o2nm_node *node, int idx)
+{
+	spin_lock(&mle->spinlock);
+
+	if (!test_bit(idx, mle->node_map))
+		mlog(0, "node %u already removed from nodemap!\n", idx);
+	else
+		clear_bit(idx, mle->node_map);
+
+	spin_unlock(&mle->spinlock);
+}
+
+static void dlm_mle_node_up(struct dlm_ctxt *dlm,
+			    struct dlm_master_list_entry *mle,
+			    struct o2nm_node *node, int idx)
+{
+	spin_lock(&mle->spinlock);
+
+	if (test_bit(idx, mle->node_map))
+		mlog(0, "node %u already in node map!\n", idx);
+	else
+		set_bit(idx, mle->node_map);
+
+	spin_unlock(&mle->spinlock);
+}
+
+
+int dlm_init_mle_cache(void)
+{
+	dlm_mle_cache = kmem_cache_create("dlm_mle_cache",
+					  sizeof(struct dlm_master_list_entry),
+					  0, SLAB_HWCACHE_ALIGN,
+					  NULL, NULL);
+	if (dlm_mle_cache == NULL)
+		return -ENOMEM;
+	return 0;
+}
+
+void dlm_destroy_mle_cache(void)
+{
+	if (dlm_mle_cache)
+		kmem_cache_destroy(dlm_mle_cache);
+}
+
+static void dlm_mle_release(struct kref *kref)
+{
+	struct dlm_master_list_entry *mle;
+	struct dlm_ctxt *dlm;
+
+	mlog_entry_void();
+
+	mle = container_of(kref, struct dlm_master_list_entry, mle_refs);
+	dlm = mle->dlm;
+
+	if (mle->type != DLM_MLE_MASTER) {
+		mlog(0, "calling mle_release for %.*s, type %d\n",
+		     mle->u.name.len, mle->u.name.name, mle->type);
+	} else {
+		mlog(0, "calling mle_release for %.*s, type %d\n",
+		     mle->u.res->lockname.len,
+		     mle->u.res->lockname.name, mle->type);
+	}
+	assert_spin_locked(&dlm->spinlock);
+	assert_spin_locked(&dlm->master_lock);
+
+	/* remove from list if not already */
+	if (!list_empty(&mle->list))
+		list_del_init(&mle->list);
+
+	/* detach the mle from the domain node up/down events */
+	__dlm_mle_detach_hb_events(dlm, mle);
+
+	/* NOTE: kfree under spinlock here.
+	 * if this is bad, we can move this to a freelist. */
+	kmem_cache_free(dlm_mle_cache, mle);
+}
+
+
+/*
+ * LOCK RESOURCE FUNCTIONS
+ */
+
+static void dlm_set_lockres_owner(struct dlm_ctxt *dlm,
+				  struct dlm_lock_resource *res,
+				  u8 owner)
+{
+	assert_spin_locked(&res->spinlock);
+
+	mlog_entry("%.*s, %u\n", res->lockname.len, res->lockname.name, owner);
+
+	if (owner == dlm->node_num)
+		atomic_inc(&dlm->local_resources);
+	else if (owner == DLM_LOCK_RES_OWNER_UNKNOWN)
+		atomic_inc(&dlm->unknown_resources);
+	else
+		atomic_inc(&dlm->remote_resources);
+
+	res->owner = owner;
+}
+
+void dlm_change_lockres_owner(struct dlm_ctxt *dlm,
+			      struct dlm_lock_resource *res, u8 owner)
+{
+	assert_spin_locked(&res->spinlock);
+
+	if (owner == res->owner)
+		return;
+
+	if (res->owner == dlm->node_num)
+		atomic_dec(&dlm->local_resources);
+	else if (res->owner == DLM_LOCK_RES_OWNER_UNKNOWN)
+		atomic_dec(&dlm->unknown_resources);
+	else
+		atomic_dec(&dlm->remote_resources);
+
+	dlm_set_lockres_owner(dlm, res, owner);
+}
+
+
+static void dlm_lockres_release(struct kref *kref)
+{
+	struct dlm_lock_resource *res;
+
+	res = container_of(kref, struct dlm_lock_resource, refs);
+
+	/* This should not happen -- all lockres' have a name
+	 * associated with them at init time. */
+	BUG_ON(!res->lockname.name);
+
+	mlog(0, "destroying lockres %.*s\n", res->lockname.len,
+	     res->lockname.name);
+
+	/* By the time we're ready to blow this guy away, we shouldn't
+	 * be on any lists. */
+	BUG_ON(!list_empty(&res->list));
+	BUG_ON(!list_empty(&res->granted));
+	BUG_ON(!list_empty(&res->converting));
+	BUG_ON(!list_empty(&res->blocked));
+	BUG_ON(!list_empty(&res->dirty));
+	BUG_ON(!list_empty(&res->recovering));
+	BUG_ON(!list_empty(&res->purge));
+
+	kfree(res->lockname.name);
+
+	kfree(res);
+}
+
+void dlm_lockres_get(struct dlm_lock_resource *res)
+{
+	kref_get(&res->refs);
+}
+
+void dlm_lockres_put(struct dlm_lock_resource *res)
+{
+	kref_put(&res->refs, dlm_lockres_release);
+}
+
+static void dlm_init_lockres(struct dlm_ctxt *dlm,
+			     struct dlm_lock_resource *res,
+			     const char *name, unsigned int namelen)
+{
+	char *qname;
+
+	/* If we memset here, we lose our reference to the kmalloc'd
+	 * res->lockname.name, so be sure to init every field
+	 * correctly! */
+
+	qname = (char *) res->lockname.name;
+	memcpy(qname, name, namelen);
+
+	res->lockname.len = namelen;
+	res->lockname.hash = full_name_hash(name, namelen);
+
+	init_waitqueue_head(&res->wq);
+	spin_lock_init(&res->spinlock);
+	INIT_LIST_HEAD(&res->list);
+	INIT_LIST_HEAD(&res->granted);
+	INIT_LIST_HEAD(&res->converting);
+	INIT_LIST_HEAD(&res->blocked);
+	INIT_LIST_HEAD(&res->dirty);
+	INIT_LIST_HEAD(&res->recovering);
+	INIT_LIST_HEAD(&res->purge);
+	atomic_set(&res->asts_reserved, 0);
+	res->migration_pending = 0;
+
+	kref_init(&res->refs);
+
+	/* just for consistency */
+	spin_lock(&res->spinlock);
+	dlm_set_lockres_owner(dlm, res, DLM_LOCK_RES_OWNER_UNKNOWN);
+	spin_unlock(&res->spinlock);
+
+	res->state = DLM_LOCK_RES_IN_PROGRESS;
+
+	res->last_used = 0;
+
+	memset(res->lvb, 0, DLM_LVB_LEN);
+}
+
+struct dlm_lock_resource *dlm_new_lockres(struct dlm_ctxt *dlm,
+				   const char *name,
+				   unsigned int namelen)
+{
+	struct dlm_lock_resource *res;
+
+	res = kmalloc(sizeof(struct dlm_lock_resource), GFP_KERNEL);
+	if (!res)
+		return NULL;
+
+	res->lockname.name = kmalloc(namelen, GFP_KERNEL);
+	if (!res->lockname.name) {
+		kfree(res);
+		return NULL;
+	}
+
+	dlm_init_lockres(dlm, res, name, namelen);
+	return res;
+}
+
+/*
+ * lookup a lock resource by name.
+ * may already exist in the hashtable.
+ * lockid is null terminated
+ *
+ * if not, allocate enough for the lockres and for
+ * the temporary structure used in doing the mastering.
+ *
+ * also, do a lookup in the dlm->master_list to see
+ * if another node has begun mastering the same lock.
+ * if so, there should be a block entry in there
+ * for this name, and we should *not* attempt to master
+ * the lock here.   need to wait around for that node
+ * to assert_master (or die).
+ *
+ */
+struct dlm_lock_resource * dlm_get_lock_resource(struct dlm_ctxt *dlm,
+					  const char *lockid,
+					  int flags)
+{
+	struct dlm_lock_resource *tmpres=NULL, *res=NULL;
+	struct dlm_master_list_entry *mle = NULL;
+	struct dlm_master_list_entry *alloc_mle = NULL;
+	int blocked = 0;
+	int ret, nodenum;
+	struct dlm_node_iter iter;
+	unsigned int namelen;
+	int tries = 0;
+
+	BUG_ON(!lockid);
+
+	namelen = strlen(lockid);
+
+	mlog(0, "get lockres %s (len %d)\n", lockid, namelen);
+
+lookup:
+	spin_lock(&dlm->spinlock);
+	tmpres = __dlm_lookup_lockres(dlm, lockid, namelen);
+	if (tmpres) {
+		spin_unlock(&dlm->spinlock);
+		mlog(0, "found in hash!\n");
+		if (res)
+			dlm_lockres_put(res);
+		res = tmpres;
+		goto leave;
+	}
+
+	if (!res) {
+		spin_unlock(&dlm->spinlock);
+		mlog(0, "allocating a new resource\n");
+		/* nothing found and we need to allocate one. */
+		alloc_mle = (struct dlm_master_list_entry *)
+			kmem_cache_alloc(dlm_mle_cache, GFP_KERNEL);
+		if (!alloc_mle)
+			goto leave;
+		res = dlm_new_lockres(dlm, lockid, namelen);
+		if (!res)
+			goto leave;
+		goto lookup;
+	}
+
+	mlog(0, "no lockres found, allocated our own: %p\n", res);
+
+	if (flags & LKM_LOCAL) {
+		/* caller knows it's safe to assume it's not mastered elsewhere
+		 * DONE!  return right away */
+		spin_lock(&res->spinlock);
+		dlm_change_lockres_owner(dlm, res, dlm->node_num);
+		__dlm_insert_lockres(dlm, res);
+		spin_unlock(&res->spinlock);
+		spin_unlock(&dlm->spinlock);
+		/* lockres still marked IN_PROGRESS */
+		goto wake_waiters;
+	}
+
+	/* check master list to see if another node has started mastering it */
+	spin_lock(&dlm->master_lock);
+
+	/* if we found a block, wait for lock to be mastered by another node */
+	blocked = dlm_find_mle(dlm, &mle, (char *)lockid, namelen);
+	if (blocked) {
+		if (mle->type == DLM_MLE_MASTER) {
+			mlog(ML_ERROR, "master entry for nonexistent lock!\n");
+			BUG();
+		} else if (mle->type == DLM_MLE_MIGRATION) {
+			/* migration is in progress! */
+			/* the good news is that we now know the
+			 * "current" master (mle->master). */
+
+			spin_unlock(&dlm->master_lock);
+			assert_spin_locked(&dlm->spinlock);
+
+			/* set the lockres owner and hash it */
+			spin_lock(&res->spinlock);
+			dlm_set_lockres_owner(dlm, res, mle->master);
+			__dlm_insert_lockres(dlm, res);
+			spin_unlock(&res->spinlock);
+			spin_unlock(&dlm->spinlock);
+
+			/* master is known, detach */
+			dlm_mle_detach_hb_events(dlm, mle);
+			dlm_put_mle(mle);
+			mle = NULL;
+			goto wake_waiters;
+		}
+	} else {
+		/* go ahead and try to master lock on this node */
+		mle = alloc_mle;
+		/* make sure this does not get freed below */
+		alloc_mle = NULL;
+		dlm_init_mle(mle, DLM_MLE_MASTER, dlm, res, NULL, 0);
+		set_bit(dlm->node_num, mle->maybe_map);
+		list_add(&mle->list, &dlm->master_list);
+	}
+
+	/* at this point there is either a DLM_MLE_BLOCK or a
+	 * DLM_MLE_MASTER on the master list, so it's safe to add the
+	 * lockres to the hashtable.  anyone who finds the lock will
+	 * still have to wait on the IN_PROGRESS. */
+
+	/* finally add the lockres to its hash bucket */
+	__dlm_insert_lockres(dlm, res);
+	/* get an extra ref on the mle in case this is a BLOCK
+	 * if so, the creator of the BLOCK may try to put the last
+	 * ref at this time in the assert master handler, so we
+	 * need an extra one to keep from a bad ptr deref. */
+	dlm_get_mle(mle);
+	spin_unlock(&dlm->master_lock);
+	spin_unlock(&dlm->spinlock);
+
+	/* must wait for lock to be mastered elsewhere */
+	if (blocked)
+		goto wait;
+
+redo_request:
+	ret = -EINVAL;
+	dlm_node_iter_init(mle->vote_map, &iter);
+	while ((nodenum = dlm_node_iter_next(&iter)) >= 0) {
+		ret = dlm_do_master_request(mle, nodenum);
+		if (ret < 0)
+			mlog_errno(ret);
+		if (mle->master != O2NM_MAX_NODES) {
+			/* found a master ! */
+			break;
+		}
+	}
+
+wait:
+	/* keep going until the response map includes all nodes */
+	ret = dlm_wait_for_lock_mastery(dlm, res, mle, &blocked);
+	if (ret < 0) {
+		mlog(0, "%s:%.*s: node map changed, redo the "
+		     "master request now, blocked=%d\n",
+		     dlm->name, res->lockname.len,
+		     res->lockname.name, blocked);
+		if (++tries > 20) {
+			mlog(ML_ERROR, "%s:%.*s: spinning on "
+			     "dlm_wait_for_lock_mastery, blocked=%d\n", 
+			     dlm->name, res->lockname.len, 
+			     res->lockname.name, blocked);
+			dlm_print_one_lock_resource(res);
+			/* dlm_print_one_mle(mle); */
+			tries = 0;
+		}
+		goto redo_request;
+	}
+
+	mlog(0, "lockres mastered by %u\n", res->owner);
+	/* make sure we never continue without this */
+	BUG_ON(res->owner == O2NM_MAX_NODES);
+
+	/* master is known, detach if not already detached */
+	dlm_mle_detach_hb_events(dlm, mle);
+	dlm_put_mle(mle);
+	/* put the extra ref */
+	dlm_put_mle(mle);
+
+wake_waiters:
+	spin_lock(&res->spinlock);
+	res->state &= ~DLM_LOCK_RES_IN_PROGRESS;
+	spin_unlock(&res->spinlock);
+	wake_up(&res->wq);
+
+leave:
+	/* need to free the unused mle */
+	if (alloc_mle)
+		kmem_cache_free(dlm_mle_cache, alloc_mle);
+
+	return res;
+}
+
+
+#define DLM_MASTERY_TIMEOUT_MS   5000
+
+static int dlm_wait_for_lock_mastery(struct dlm_ctxt *dlm,
+				     struct dlm_lock_resource *res,
+				     struct dlm_master_list_entry *mle,
+				     int *blocked)
+{
+	u8 m;
+	int ret, bit;
+	int map_changed, voting_done;
+	int assert, sleep;
+
+recheck:
+	ret = 0;
+	assert = 0;
+
+	/* check if another node has already become the owner */
+	spin_lock(&res->spinlock);
+	if (res->owner != DLM_LOCK_RES_OWNER_UNKNOWN) {
+		spin_unlock(&res->spinlock);
+		goto leave;
+	}
+	spin_unlock(&res->spinlock);
+
+	spin_lock(&mle->spinlock);
+	m = mle->master;
+	map_changed = (memcmp(mle->vote_map, mle->node_map,
+			      sizeof(mle->vote_map)) != 0);
+	voting_done = (memcmp(mle->vote_map, mle->response_map,
+			     sizeof(mle->vote_map)) == 0);
+
+	/* restart if we hit any errors */
+	if (map_changed) {
+		int b;
+		mlog(0, "%s: %.*s: node map changed, restarting\n",
+		     dlm->name, res->lockname.len, res->lockname.name);
+		ret = dlm_restart_lock_mastery(dlm, res, mle, *blocked);
+		b = (mle->type == DLM_MLE_BLOCK);
+		if ((*blocked && !b) || (!*blocked && b)) {
+			mlog(0, "%s:%.*s: status change: old=%d new=%d\n", 
+			     dlm->name, res->lockname.len, res->lockname.name,
+			     *blocked, b);
+			*blocked = b;
+		}
+		spin_unlock(&mle->spinlock);
+		if (ret < 0) {
+			mlog_errno(ret);
+			goto leave;
+		}
+		mlog(0, "%s:%.*s: restart lock mastery succeeded, "
+		     "rechecking now\n", dlm->name, res->lockname.len,
+		     res->lockname.name);
+		goto recheck;
+	}
+
+	if (m != O2NM_MAX_NODES) {
+		/* another node has done an assert!
+		 * all done! */
+		sleep = 0;
+	} else {
+		sleep = 1;
+		/* have all nodes responded? */
+		if (voting_done && !*blocked) {
+			bit = find_next_bit(mle->maybe_map, O2NM_MAX_NODES, 0);
+			if (dlm->node_num <= bit) {
+				/* my node number is lowest.
+			 	 * now tell other nodes that I am
+				 * mastering this. */
+				mle->master = dlm->node_num;
+				assert = 1;
+				sleep = 0;
+			}
+			/* if voting is done, but we have not received
+			 * an assert master yet, we must sleep */
+		}
+	}
+
+	spin_unlock(&mle->spinlock);
+
+	/* sleep if we haven't finished voting yet */
+	if (sleep) {
+		unsigned long timeo = msecs_to_jiffies(DLM_MASTERY_TIMEOUT_MS);
+
+		/*
+		if (atomic_read(&mle->mle_refs.refcount) < 2)
+			mlog(ML_ERROR, "mle (%p) refs=%d, name=%.*s\n", mle,
+			atomic_read(&mle->mle_refs.refcount),
+			res->lockname.len, res->lockname.name);
+		*/
+		atomic_set(&mle->woken, 0);
+		(void)wait_event_timeout(mle->wq,
+					 (atomic_read(&mle->woken) == 1),
+					 timeo);
+		if (res->owner == O2NM_MAX_NODES) {
+			mlog(0, "waiting again\n");
+			goto recheck;
+		}
+		mlog(0, "done waiting, master is %u\n", res->owner);
+		ret = 0;
+		goto leave;
+	}
+
+	ret = 0;   /* done */
+	if (assert) {
+		m = dlm->node_num;
+		mlog(0, "about to master %.*s here, this=%u\n",
+		     res->lockname.len, res->lockname.name, m);
+		ret = dlm_do_assert_master(dlm, res->lockname.name,
+					   res->lockname.len, mle->vote_map, 0);
+		if (ret) {
+			/* This is a failure in the network path,
+			 * not in the response to the assert_master
+			 * (any nonzero response is a BUG on this node).
+			 * Most likely a socket just got disconnected
+			 * due to node death. */
+			mlog_errno(ret);
+		}
+		/* no longer need to restart lock mastery.
+		 * all living nodes have been contacted. */
+		ret = 0;
+	}
+
+	/* set the lockres owner */
+	spin_lock(&res->spinlock);
+	dlm_change_lockres_owner(dlm, res, m);
+	spin_unlock(&res->spinlock);
+
+leave:
+	return ret;
+}
+
+struct dlm_bitmap_diff_iter
+{
+	int curnode;
+	unsigned long *orig_bm;
+	unsigned long *cur_bm;
+	unsigned long diff_bm[BITS_TO_LONGS(O2NM_MAX_NODES)];
+};
+
+enum dlm_node_state_change
+{
+	NODE_DOWN = -1,
+	NODE_NO_CHANGE = 0,
+	NODE_UP
+};
+
+static void dlm_bitmap_diff_iter_init(struct dlm_bitmap_diff_iter *iter,
+				      unsigned long *orig_bm,
+				      unsigned long *cur_bm)
+{
+	unsigned long p1, p2;
+	int i;
+
+	iter->curnode = -1;
+	iter->orig_bm = orig_bm;
+	iter->cur_bm = cur_bm;
+
+	for (i = 0; i < BITS_TO_LONGS(O2NM_MAX_NODES); i++) {
+       		p1 = *(iter->orig_bm + i);
+	       	p2 = *(iter->cur_bm + i);
+		iter->diff_bm[i] = (p1 & ~p2) | (p2 & ~p1);
+	}
+}
+
+static int dlm_bitmap_diff_iter_next(struct dlm_bitmap_diff_iter *iter,
+				     enum dlm_node_state_change *state)
+{
+	int bit;
+
+	if (iter->curnode >= O2NM_MAX_NODES)
+		return -ENOENT;
+
+	bit = find_next_bit(iter->diff_bm, O2NM_MAX_NODES,
+			    iter->curnode+1);
+	if (bit >= O2NM_MAX_NODES) {
+		iter->curnode = O2NM_MAX_NODES;
+		return -ENOENT;
+	}
+
+	/* if it was there in the original then this node died */
+	if (test_bit(bit, iter->orig_bm))
+		*state = NODE_DOWN;
+	else
+		*state = NODE_UP;
+
+	iter->curnode = bit;
+	return bit;
+}
+
+
+static int dlm_restart_lock_mastery(struct dlm_ctxt *dlm,
+				    struct dlm_lock_resource *res,
+				    struct dlm_master_list_entry *mle,
+				    int blocked)
+{
+	struct dlm_bitmap_diff_iter bdi;
+	enum dlm_node_state_change sc;
+	int node;
+	int ret = 0;
+
+	mlog(0, "something happened such that the "
+	     "master process may need to be restarted!\n");
+
+	assert_spin_locked(&mle->spinlock);
+
+	dlm_bitmap_diff_iter_init(&bdi, mle->vote_map, mle->node_map);
+	node = dlm_bitmap_diff_iter_next(&bdi, &sc);
+	while (node >= 0) {
+		if (sc == NODE_UP) {
+			/* a node came up.  easy.  might not even need
+			 * to talk to it if its node number is higher
+			 * or if we are already blocked. */
+			mlog(0, "node up! %d\n", node);
+			if (blocked)
+				goto next;
+
+			if (node > dlm->node_num) {
+				mlog(0, "node > this node. skipping.\n");
+				goto next;
+			}
+
+			/* redo the master request, but only for the new node */
+			mlog(0, "sending request to new node\n");
+			clear_bit(node, mle->response_map);
+			set_bit(node, mle->vote_map);
+		} else {
+			mlog(ML_ERROR, "node down! %d\n", node);
+
+			/* if the node wasn't involved in mastery skip it,
+			 * but clear it out from the maps so that it will
+			 * not affect mastery of this lockres */
+			clear_bit(node, mle->response_map);
+			clear_bit(node, mle->vote_map);
+			if (!test_bit(node, mle->maybe_map))
+				goto next;
+
+			/* if we're already blocked on lock mastery, and the
+			 * dead node wasn't the expected master, or there is
+			 * another node in the maybe_map, keep waiting */
+			if (blocked) {
+				int lowest = find_next_bit(mle->maybe_map,
+						       O2NM_MAX_NODES, 0);
+
+				/* act like it was never there */
+				clear_bit(node, mle->maybe_map);
+
+			       	if (node != lowest)
+					goto next;
+
+				mlog(ML_ERROR, "expected master %u died while "
+				     "this node was blocked waiting on it!\n",
+				     node);
+				lowest = find_next_bit(mle->maybe_map,
+						       O2NM_MAX_NODES,
+						       lowest+1);
+				if (lowest < O2NM_MAX_NODES) {
+					mlog(0, "still blocked. waiting "
+					     "on %u now\n", lowest);
+					goto next;
+				}
+
+				/* mle is an MLE_BLOCK, but there is now
+				 * nothing left to block on.  we need to return
+				 * all the way back out and try again with
+				 * an MLE_MASTER. dlm_do_local_recovery_cleanup
+				 * has already run, so the mle refcount is ok */
+				mlog(0, "no longer blocking. we can "
+				     "try to master this here\n");
+				mle->type = DLM_MLE_MASTER;
+				memset(mle->maybe_map, 0,
+				       sizeof(mle->maybe_map));
+				memset(mle->response_map, 0,
+				       sizeof(mle->maybe_map));
+				memcpy(mle->vote_map, mle->node_map,
+				       sizeof(mle->node_map));
+				mle->u.res = res;
+				set_bit(dlm->node_num, mle->maybe_map);
+
+				ret = -EAGAIN;
+				goto next;
+			}
+
+			clear_bit(node, mle->maybe_map);
+			if (node > dlm->node_num)
+				goto next;
+
+			mlog(0, "dead node in map!\n");
+			/* yuck. go back and re-contact all nodes
+			 * in the vote_map, removing this node. */
+			memset(mle->response_map, 0,
+			       sizeof(mle->response_map));
+		}
+		ret = -EAGAIN;
+next:
+		node = dlm_bitmap_diff_iter_next(&bdi, &sc);
+	}
+	return ret;
+}
+
+
+/*
+ * DLM_MASTER_REQUEST_MSG
+ *
+ * returns: 0 on success,
+ *          -errno on a network error
+ *
+ * on error, the caller should assume the target node is "dead"
+ *