path: root/drivers/md/dm-snap.c

/*
 * dm-snapshot.c
 *
 * Copyright (C) 2001-2002 Sistina Software (UK) Limited.
 *
 * This file is released under the GPL.
 */

#include <linux/blkdev.h>
#include <linux/ctype.h>
#include <linux/device-mapper.h>
#include <linux/delay.h>
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/kdev_t.h>
#include <linux/list.h>
#include <linux/mempool.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>
#include <linux/log2.h>
#include <linux/dm-kcopyd.h>

#include "dm-exception-store.h"
#include "dm-snap.h"
#include "dm-bio-list.h"

#define DM_MSG_PREFIX "snapshots"

/*
 * The percentage increment we will wake up users at
 */
#define WAKE_UP_PERCENT 5

/*
 * kcopyd priority of snapshot operations
 */
#define SNAPSHOT_COPY_PRIORITY 2

/*
 * Reserve 1MB for each snapshot initially (with minimum of 1 page).
 */
#define SNAPSHOT_PAGES (((1UL << 20) >> PAGE_SHIFT) ? : 1)

/*
 * The size of the mempool used to track chunks in use.
 */
#define MIN_IOS 256

static struct workqueue_struct *ksnapd;
static void flush_queued_bios(struct work_struct *work);

struct dm_snap_pending_exception {
	struct dm_snap_exception e;

	/*
	 * Origin buffers waiting for this to