android_kernel_motorola_sm6225/drivers/md/dm-snap.h

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/*
* Copyright (C) 2001-2002 Sistina Software (UK) Limited.
*
* This file is released under the GPL.
*/
#ifndef DM_SNAPSHOT_H
#define DM_SNAPSHOT_H
#include <linux/device-mapper.h>
#include "dm-exception-store.h"
#include "dm-bio-list.h"
#include <linux/blkdev.h>
#include <linux/workqueue.h>
struct exception_table {
uint32_t hash_mask;
unsigned hash_shift;
struct list_head *table;
};
#define DM_TRACKED_CHUNK_HASH_SIZE 16
#define DM_TRACKED_CHUNK_HASH(x) ((unsigned long)(x) & \
(DM_TRACKED_CHUNK_HASH_SIZE - 1))
struct dm_snapshot {
struct rw_semaphore lock;
struct dm_target *ti;
struct dm_dev *origin;
struct dm_dev *cow;
/* List of snapshots per Origin */
struct list_head list;
/* Size of data blocks saved - must be a power of 2 */
chunk_t chunk_size;
chunk_t chunk_mask;
chunk_t chunk_shift;
/* You can't use a snapshot if this is 0 (e.g. if full) */
int valid;
/* Origin writes don't trigger exceptions until this is set */
int active;
/* Used for display of table */
char type;
mempool_t *pending_pool;
dm snapshot: wait for chunks in destructor If there are several snapshots sharing an origin and one is removed while the origin is being written to, the snapshot's mempool may get deleted while elements are still referenced. Prior to dm-snapshot-use-per-device-mempools.patch the pending exceptions may still have been referenced after the snapshot was destroyed, but this was not a problem because the shared mempool was still there. This patch fixes the problem by tracking the number of mempool elements in use. The scenario: - You have an origin and two snapshots 1 and 2. - Someone writes to the origin. - It creates two exceptions in the snapshots, snapshot 1 will be primary exception, snapshot 2's pending_exception->primary_pe will point to the exception in snapshot 1. - The exceptions are being relocated, relocation of exception 1 finishes (but it's pending_exception is still allocated, because it is referenced by an exception from snapshot 2) - The user lvremoves snapshot 1 --- it calls just suspend (does nothing) and destructor. md->pending is zero (there is no I/O submitted to the snapshot by md layer), so it won't help us. - The destructor waits for kcopyd jobs to finish on snapshot 1 --- but there are none. - The destructor on snapshot 1 cleans up everything. - The relocation of exception on snapshot 2 finishes, it drops reference on primary_pe. This frees its primary_pe pointer. Primary_pe points to pending exception created for snapshot 1. So it frees memory into non-existing mempool. Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2008-10-30 14:33:16 +01:00
atomic_t pending_exceptions_count;
struct exception_table pending;
struct exception_table complete;
/*
* pe_lock protects all pending_exception operations and access
* as well as the snapshot_bios list.
*/
spinlock_t pe_lock;
/* The on disk metadata handler */
struct dm_exception_store store;
struct dm_kcopyd_client *kcopyd_client;
/* Queue of snapshot writes for ksnapd to flush */
struct bio_list queued_bios;
struct work_struct queued_bios_work;
/* Chunks with outstanding reads */
mempool_t *tracked_chunk_pool;
spinlock_t tracked_chunk_lock;
struct hlist_head tracked_chunk_hash[DM_TRACKED_CHUNK_HASH_SIZE];
};
/*
* Return the number of sectors in the device.
*/
static inline sector_t get_dev_size(struct block_device *bdev)
{
return bdev->bd_inode->i_size >> SECTOR_SHIFT;
}
static inline chunk_t sector_to_chunk(struct dm_snapshot *s, sector_t sector)
{
return (sector & ~s->chunk_mask) >> s->chunk_shift;
}
static inline sector_t chunk_to_sector(struct dm_snapshot *s, chunk_t chunk)
{
return chunk << s->chunk_shift;
}
static inline int bdev_equal(struct block_device *lhs, struct block_device *rhs)
{
/*
* There is only ever one instance of a particular block
* device so we can compare pointers safely.
*/
return lhs == rhs;
}
#endif