tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
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linux
1/*
2 * dm-snapshot.c
3 *
4 * Copyright (C) 2001-2002 Sistina Software (UK) Limited.
5 *
6 * This file is released under the GPL.
7 */
8
9#ifndef DM_SNAPSHOT_H
10#define DM_SNAPSHOT_H
11
12#include "dm.h"
13#include <linux/blkdev.h>
14
15struct exception_table {
16 uint32_t hash_mask;
17 struct list_head *table;
18};
19
20/*
21 * The snapshot code deals with largish chunks of the disk at a
22 * time. Typically 64k - 256k.
23 */
24/* FIXME: can we get away with limiting these to a uint32_t ? */
25typedef sector_t chunk_t;
26
27/*
28 * An exception is used where an old chunk of data has been
29 * replaced by a new one.
30 */
31struct exception {
32 struct list_head hash_list;
33
34 chunk_t old_chunk;
35 chunk_t new_chunk;
36};
37
38/*
39 * Abstraction to handle the meta/layout of exception stores (the
40 * COW device).
41 */
42struct exception_store {
43
44 /*
45 * Destroys this object when you've finished with it.
46 */
47 void (*destroy) (struct exception_store *store);
48
49 /*
50 * The target shouldn't read the COW device until this is
51 * called.
52 */
53 int (*read_metadata) (struct exception_store *store);
54
55 /*
56 * Find somewhere to store the next exception.
57 */
58 int (*prepare_exception) (struct exception_store *store,
59 struct exception *e);
60
61 /*
62 * Update the metadata with this exception.
63 */
64 void (*commit_exception) (struct exception_store *store,
65 struct exception *e,
66 void (*callback) (void *, int success),
67 void *callback_context);
68
69 /*
70 * The snapshot is invalid, note this in the metadata.
71 */
72 void (*drop_snapshot) (struct exception_store *store);
73
74 /*
75 * Return how full the snapshot is.
76 */
77 void (*fraction_full) (struct exception_store *store,
78 sector_t *numerator,
79 sector_t *denominator);
80
81 struct dm_snapshot *snap;
82 void *context;
83};
84
85struct dm_snapshot {
86 struct rw_semaphore lock;
87 struct dm_table *table;
88
89 struct dm_dev *origin;
90 struct dm_dev *cow;
91
92 /* List of snapshots per Origin */
93 struct list_head list;
94
95 /* Size of data blocks saved - must be a power of 2 */
96 chunk_t chunk_size;
97 chunk_t chunk_mask;
98 chunk_t chunk_shift;
99
100 /* You can't use a snapshot if this is 0 (e.g. if full) */
101 int valid;
102 int have_metadata;
103
104 /* Used for display of table */
105 char type;
106
107 /* The last percentage we notified */
108 int last_percent;
109
110 struct exception_table pending;
111 struct exception_table complete;
112
113 /* The on disk metadata handler */
114 struct exception_store store;
115
116 struct kcopyd_client *kcopyd_client;
117};
118
119/*
120 * Used by the exception stores to load exceptions hen
121 * initialising.
122 */
123int dm_add_exception(struct dm_snapshot *s, chunk_t old, chunk_t new);
124
125/*
126 * Constructor and destructor for the default persistent
127 * store.
128 */
129int dm_create_persistent(struct exception_store *store, uint32_t chunk_size);
130
131int dm_create_transient(struct exception_store *store,
132 struct dm_snapshot *s, int blocksize);
133
134/*
135 * Return the number of sectors in the device.
136 */
137static inline sector_t get_dev_size(struct block_device *bdev)
138{
139 return bdev->bd_inode->i_size >> SECTOR_SHIFT;
140}
141
142static inline chunk_t sector_to_chunk(struct dm_snapshot *s, sector_t sector)
143{
144 return (sector & ~s->chunk_mask) >> s->chunk_shift;
145}
146
147static inline sector_t chunk_to_sector(struct dm_snapshot *s, chunk_t chunk)
148{
149 return chunk << s->chunk_shift;
150}
151
152static inline int bdev_equal(struct block_device *lhs, struct block_device *rhs)
153{
154 /*
155 * There is only ever one instance of a particular block
156 * device so we can compare pointers safely.
157 */
158 return lhs == rhs;
159}
160
161#endif