path: root/drivers/block/drbd/drbd_actlog.c

/*
   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/crc32c.h>
#include <linux/drbd.h>
#include <linux/drbd_limits.h>
#include <linux/dynamic_debug.h>
#include "drbd_int.h"
#include "drbd_wrappers.h"


enum al_transaction_types {
	AL_TR_UPDATE = 0,
	AL_TR_INITIALIZED = 0xffff
};
/* all fields on disc in big endian */
struct __packed al_transaction_on_disk {
	/* don't we all like magic */
	__be32	magic;

	/* to identify the most recent transaction block
	 * in the on disk ring buffer */
	__be32	tr_number;

	/* checksum on the full 4k block, with this field set to 0. */
	__be32	crc32c;

	/* type of transaction, special transaction types like:
	 * purge-all, set-all-idle, set-all-active, ... to-be-defined
	 * see also enum al_transaction_types */
	__be16	transaction_type;

	/* we currently allow only a few thousand extents,
	 * so 16bit will be enough for the slot number. */

	/* how many updates in this transaction */
	__be16	n_updates;

	/* maximum slot number, "al-extents" in drbd.conf speak.
	 * Having this in each transaction should make reconfiguration
	 * of that parameter easier. */
	__be16	context_size;

	/* slot number the context starts with */
	__be16	context_start_slot_nr;

	/* Some reserved bytes.  Expected usage is a 64bit counter of
	 * sectors-written since device creation, and other data generation tag
	 * supporting usage */
	__be32	__reserved[4];

	/* --- 36 byte used --- */

	/* Reserve space for up to AL_UPDATES_PER_TRANSACTION changes
	 * in one transaction, then use the remaining byte in the 4k block for
	 * context information.  "Flexible" number of updates per transaction
	 * does not help, as we have to account for the case when all update
	 * slots are used anyways, so it would only complicate code without
	 * additional benefit.
	 */
	__be16	update_slot_nr[AL_UPDATES_PER_TRANSACTION];

	/* but the extent number is 32bit, which at an extent size of 4 MiB
	 * allows to cover device sizes of up to 2**54 Byte (16 PiB) */
	__be32	update_extent_nr[AL_UPDATES_PER_TRANSACTION];

	/* --- 420 bytes used (36 + 64*6) --- */

	/* 4096 - 420 = 3676 = 919 * 4 */
	__be32	context[AL_CONTEXT_PER_TRANSACTION];
};

struct update_odbm_work {
	struct drbd_work w;
	unsigned int enr;
};

struct update_al_work {
	struct drbd_work w;
	struct completion event;
	int err;
};


void *drbd_md_get_buffer(struct drbd_conf *mdev)
{
	int r;

	wait_event(mdev->misc_wait,
		   (r = atomic_cmpxchg(&mdev->md_io_in_use, 0, 1)) == 0 ||
		   mdev->state.disk <= D_FAILED);

	return r ? NULL : page_address(mdev->md_io_page);
}

void <