drivers/md/dm-snap.h

   1 /*
   2  * Copyright (C) 2001-2002 Sistina Software (UK) Limited.
   3  *
   4  * This file is released under the GPL.
   5  */
   6
   7 #ifndef DM_SNAPSHOT_H
   8 #define DM_SNAPSHOT_H
   9
  10 #include <linux/device-mapper.h>
  11 #include "dm-exception-store.h"
  12 #include "dm-bio-list.h"
  13 #include <linux/blkdev.h>
  14 #include <linux/workqueue.h>
  15
  16 struct exception_table {
  17         uint32_t hash_mask;
  18         unsigned hash_shift;
  19         struct list_head *table;
  20 };
  21
  22 #define DM_TRACKED_CHUNK_HASH_SIZE      16
  23 #define DM_TRACKED_CHUNK_HASH(x)        ((unsigned long)(x) & \
  24                                          (DM_TRACKED_CHUNK_HASH_SIZE - 1))
  25
  26 struct dm_snapshot {
  27         struct rw_semaphore lock;
  28         struct dm_target *ti;
  29
  30         struct dm_dev *origin;
  31         struct dm_dev *cow;
  32
  33         /* List of snapshots per Origin */
  34         struct list_head list;
  35
  36         /* Size of data blocks saved - must be a power of 2 */
  37         chunk_t chunk_size;
  38         chunk_t chunk_mask;
  39         chunk_t chunk_shift;
  40
  41         /* You can't use a snapshot if this is 0 (e.g. if full) */
  42         int valid;
  43
  44         /* Origin writes don't trigger exceptions until this is set */
  45         int active;
  46
  47         /* Used for display of table */
  48         char type;
  49
  50         mempool_t *pending_pool;
  51
  52         atomic_t pending_exceptions_count;
  53
  54         struct exception_table pending;
  55         struct exception_table complete;
  56
  57         /*
  58          * pe_lock protects all pending_exception operations and access
  59          * as well as the snapshot_bios list.
  60          */
  61         spinlock_t pe_lock;
  62
  63         /* The on disk metadata handler */
  64         struct dm_exception_store store;
  65
  66         struct dm_kcopyd_client *kcopyd_client;
  67
  68         /* Queue of snapshot writes for ksnapd to flush */
  69         struct bio_list queued_bios;
  70         struct work_struct queued_bios_work;
  71
  72         /* Chunks with outstanding reads */
  73         mempool_t *tracked_chunk_pool;
  74         spinlock_t tracked_chunk_lock;
  75         struct hlist_head tracked_chunk_hash[DM_TRACKED_CHUNK_HASH_SIZE];
  76 };
  77
  78 /*
  79  * Return the number of sectors in the device.
  80  */
  81 static inline sector_t get_dev_size(struct block_device *bdev)
  82 {
  83         return bdev->bd_inode->i_size >> SECTOR_SHIFT;
  84 }
  85
  86 static inline chunk_t sector_to_chunk(struct dm_snapshot *s, sector_t sector)
  87 {
  88         return (sector & ~s->chunk_mask) >> s->chunk_shift;
  89 }
  90
  91 static inline sector_t chunk_to_sector(struct dm_snapshot *s, chunk_t chunk)
  92 {
  93         return chunk << s->chunk_shift;
  94 }
  95
  96 static inline int bdev_equal(struct block_device *lhs, struct block_device *rhs)
  97 {
  98         /*
  99          * There is only ever one instance of a particular block
 100          * device so we can compare pointers safely.
 101          */
 102         return lhs == rhs;
 103 }
 104
 105 #endif