2 * Copyright (C) 2001-2002 Sistina Software (UK) Limited.
3 * Copyright (C) 2008 Red Hat, Inc. All rights reserved.
5 * Device-mapper snapshot exception store.
7 * This file is released under the GPL.
10 #ifndef _LINUX_DM_EXCEPTION_STORE
11 #define _LINUX_DM_EXCEPTION_STORE
13 #include <linux/blkdev.h>
16 * The snapshot code deals with largish chunks of the disk at a
17 * time. Typically 32k - 512k.
19 typedef sector_t chunk_t;
22 * An exception is used where an old chunk of data has been
23 * replaced by a new one.
24 * If chunk_t is 64 bits in size, the top 8 bits of new_chunk hold the number
25 * of chunks that follow contiguously. Remaining bits hold the number of the
26 * chunk within the device.
28 struct dm_snap_exception {
29 struct list_head hash_list;
36 * Abstraction to handle the meta/layout of exception stores (the
39 struct exception_store {
41 * Destroys this object when you've finished with it.
43 void (*destroy) (struct exception_store *store);
46 * The target shouldn't read the COW device until this is
49 int (*read_metadata) (struct exception_store *store);
52 * Find somewhere to store the next exception.
54 int (*prepare_exception) (struct exception_store *store,
55 struct dm_snap_exception *e);
58 * Update the metadata with this exception.
60 void (*commit_exception) (struct exception_store *store,
61 struct dm_snap_exception *e,
62 void (*callback) (void *, int success),
63 void *callback_context);
66 * The snapshot is invalid, note this in the metadata.
68 void (*drop_snapshot) (struct exception_store *store);
71 * Return how full the snapshot is.
73 void (*fraction_full) (struct exception_store *store,
75 sector_t *denominator);
77 struct dm_snapshot *snap;
82 * Funtions to manipulate consecutive chunks
84 # if defined(CONFIG_LBD) || (BITS_PER_LONG == 64)
85 # define DM_CHUNK_CONSECUTIVE_BITS 8
86 # define DM_CHUNK_NUMBER_BITS 56
88 static inline chunk_t dm_chunk_number(chunk_t chunk)
90 return chunk & (chunk_t)((1ULL << DM_CHUNK_NUMBER_BITS) - 1ULL);
93 static inline unsigned dm_consecutive_chunk_count(struct dm_snap_exception *e)
95 return e->new_chunk >> DM_CHUNK_NUMBER_BITS;
98 static inline void dm_consecutive_chunk_count_inc(struct dm_snap_exception *e)
100 e->new_chunk += (1ULL << DM_CHUNK_NUMBER_BITS);
102 BUG_ON(!dm_consecutive_chunk_count(e));
106 # define DM_CHUNK_CONSECUTIVE_BITS 0
108 static inline chunk_t dm_chunk_number(chunk_t chunk)
113 static inline unsigned dm_consecutive_chunk_count(struct dm_snap_exception *e)
118 static inline void dm_consecutive_chunk_count_inc(struct dm_snap_exception *e)
125 * Two exception store implementations.
127 int dm_create_persistent(struct exception_store *store);
129 int dm_create_transient(struct exception_store *store);
131 #endif /* _LINUX_DM_EXCEPTION_STORE */