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aea53d92 JB |
1 | /* |
2 | * Copyright (C) 2001-2002 Sistina Software (UK) Limited. | |
3 | * Copyright (C) 2008 Red Hat, Inc. All rights reserved. | |
4 | * | |
5 | * Device-mapper snapshot exception store. | |
6 | * | |
7 | * This file is released under the GPL. | |
8 | */ | |
9 | ||
10 | #ifndef _LINUX_DM_EXCEPTION_STORE | |
11 | #define _LINUX_DM_EXCEPTION_STORE | |
12 | ||
13 | #include <linux/blkdev.h> | |
14 | ||
15 | /* | |
16 | * The snapshot code deals with largish chunks of the disk at a | |
17 | * time. Typically 32k - 512k. | |
18 | */ | |
19 | typedef sector_t chunk_t; | |
20 | ||
21 | /* | |
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. | |
27 | */ | |
28 | struct dm_snap_exception { | |
29 | struct list_head hash_list; | |
30 | ||
31 | chunk_t old_chunk; | |
32 | chunk_t new_chunk; | |
33 | }; | |
34 | ||
35 | /* | |
36 | * Abstraction to handle the meta/layout of exception stores (the | |
37 | * COW device). | |
38 | */ | |
1ae25f9c JB |
39 | struct dm_exception_store { |
40 | ||
aea53d92 JB |
41 | /* |
42 | * Destroys this object when you've finished with it. | |
43 | */ | |
1ae25f9c | 44 | void (*destroy) (struct dm_exception_store *store); |
aea53d92 JB |
45 | |
46 | /* | |
47 | * The target shouldn't read the COW device until this is | |
48 | * called. | |
49 | */ | |
1ae25f9c | 50 | int (*read_metadata) (struct dm_exception_store *store); |
aea53d92 JB |
51 | |
52 | /* | |
53 | * Find somewhere to store the next exception. | |
54 | */ | |
1ae25f9c | 55 | int (*prepare_exception) (struct dm_exception_store *store, |
aea53d92 JB |
56 | struct dm_snap_exception *e); |
57 | ||
58 | /* | |
59 | * Update the metadata with this exception. | |
60 | */ | |
1ae25f9c | 61 | void (*commit_exception) (struct dm_exception_store *store, |
aea53d92 JB |
62 | struct dm_snap_exception *e, |
63 | void (*callback) (void *, int success), | |
64 | void *callback_context); | |
65 | ||
66 | /* | |
67 | * The snapshot is invalid, note this in the metadata. | |
68 | */ | |
1ae25f9c | 69 | void (*drop_snapshot) (struct dm_exception_store *store); |
aea53d92 JB |
70 | |
71 | /* | |
72 | * Return how full the snapshot is. | |
73 | */ | |
1ae25f9c | 74 | void (*fraction_full) (struct dm_exception_store *store, |
aea53d92 JB |
75 | sector_t *numerator, |
76 | sector_t *denominator); | |
77 | ||
78 | struct dm_snapshot *snap; | |
79 | void *context; | |
80 | }; | |
81 | ||
82 | /* | |
83 | * Funtions to manipulate consecutive chunks | |
84 | */ | |
85 | # if defined(CONFIG_LBD) || (BITS_PER_LONG == 64) | |
86 | # define DM_CHUNK_CONSECUTIVE_BITS 8 | |
87 | # define DM_CHUNK_NUMBER_BITS 56 | |
88 | ||
89 | static inline chunk_t dm_chunk_number(chunk_t chunk) | |
90 | { | |
91 | return chunk & (chunk_t)((1ULL << DM_CHUNK_NUMBER_BITS) - 1ULL); | |
92 | } | |
93 | ||
94 | static inline unsigned dm_consecutive_chunk_count(struct dm_snap_exception *e) | |
95 | { | |
96 | return e->new_chunk >> DM_CHUNK_NUMBER_BITS; | |
97 | } | |
98 | ||
99 | static inline void dm_consecutive_chunk_count_inc(struct dm_snap_exception *e) | |
100 | { | |
101 | e->new_chunk += (1ULL << DM_CHUNK_NUMBER_BITS); | |
102 | ||
103 | BUG_ON(!dm_consecutive_chunk_count(e)); | |
104 | } | |
105 | ||
106 | # else | |
107 | # define DM_CHUNK_CONSECUTIVE_BITS 0 | |
108 | ||
109 | static inline chunk_t dm_chunk_number(chunk_t chunk) | |
110 | { | |
111 | return chunk; | |
112 | } | |
113 | ||
114 | static inline unsigned dm_consecutive_chunk_count(struct dm_snap_exception *e) | |
115 | { | |
116 | return 0; | |
117 | } | |
118 | ||
119 | static inline void dm_consecutive_chunk_count_inc(struct dm_snap_exception *e) | |
120 | { | |
121 | } | |
122 | ||
123 | # endif | |
124 | ||
4db6bfe0 AK |
125 | int dm_exception_store_init(void); |
126 | void dm_exception_store_exit(void); | |
127 | ||
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128 | /* |
129 | * Two exception store implementations. | |
130 | */ | |
4db6bfe0 AK |
131 | int dm_persistent_snapshot_init(void); |
132 | void dm_persistent_snapshot_exit(void); | |
133 | ||
134 | int dm_transient_snapshot_init(void); | |
135 | void dm_transient_snapshot_exit(void); | |
136 | ||
1ae25f9c | 137 | int dm_create_persistent(struct dm_exception_store *store); |
aea53d92 | 138 | |
1ae25f9c | 139 | int dm_create_transient(struct dm_exception_store *store); |
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140 | |
141 | #endif /* _LINUX_DM_EXCEPTION_STORE */ |