Root/drivers/md/dm-exception-store.h

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#include <linux/device-mapper.h>
15
16/*
17 * The snapshot code deals with largish chunks of the disk at a
18 * time. Typically 32k - 512k.
19 */
20typedef sector_t chunk_t;
21
22/*
23 * An exception is used where an old chunk of data has been
24 * replaced by a new one.
25 * If chunk_t is 64 bits in size, the top 8 bits of new_chunk hold the number
26 * of chunks that follow contiguously. Remaining bits hold the number of the
27 * chunk within the device.
28 */
29struct dm_exception {
30    struct list_head hash_list;
31
32    chunk_t old_chunk;
33    chunk_t new_chunk;
34};
35
36/*
37 * Abstraction to handle the meta/layout of exception stores (the
38 * COW device).
39 */
40struct dm_exception_store;
41struct dm_exception_store_type {
42    const char *name;
43    struct module *module;
44
45    int (*ctr) (struct dm_exception_store *store,
46            unsigned argc, char **argv);
47
48    /*
49     * Destroys this object when you've finished with it.
50     */
51    void (*dtr) (struct dm_exception_store *store);
52
53    /*
54     * The target shouldn't read the COW device until this is
55     * called. As exceptions are read from the COW, they are
56     * reported back via the callback.
57     */
58    int (*read_metadata) (struct dm_exception_store *store,
59                  int (*callback)(void *callback_context,
60                          chunk_t old, chunk_t new),
61                  void *callback_context);
62
63    /*
64     * Find somewhere to store the next exception.
65     */
66    int (*prepare_exception) (struct dm_exception_store *store,
67                  struct dm_exception *e);
68
69    /*
70     * Update the metadata with this exception.
71     */
72    void (*commit_exception) (struct dm_exception_store *store,
73                  struct dm_exception *e,
74                  void (*callback) (void *, int success),
75                  void *callback_context);
76
77    /*
78     * Returns 0 if the exception store is empty.
79     *
80     * If there are exceptions still to be merged, sets
81     * *last_old_chunk and *last_new_chunk to the most recent
82     * still-to-be-merged chunk and returns the number of
83     * consecutive previous ones.
84     */
85    int (*prepare_merge) (struct dm_exception_store *store,
86                  chunk_t *last_old_chunk, chunk_t *last_new_chunk);
87
88    /*
89     * Clear the last n exceptions.
90     * nr_merged must be <= the value returned by prepare_merge.
91     */
92    int (*commit_merge) (struct dm_exception_store *store, int nr_merged);
93
94    /*
95     * The snapshot is invalid, note this in the metadata.
96     */
97    void (*drop_snapshot) (struct dm_exception_store *store);
98
99    unsigned (*status) (struct dm_exception_store *store,
100                status_type_t status, char *result,
101                unsigned maxlen);
102
103    /*
104     * Return how full the snapshot is.
105     */
106    void (*usage) (struct dm_exception_store *store,
107               sector_t *total_sectors, sector_t *sectors_allocated,
108               sector_t *metadata_sectors);
109
110    /* For internal device-mapper use only. */
111    struct list_head list;
112};
113
114struct dm_snapshot;
115
116struct dm_exception_store {
117    struct dm_exception_store_type *type;
118    struct dm_snapshot *snap;
119
120    /* Size of data blocks saved - must be a power of 2 */
121    unsigned chunk_size;
122    unsigned chunk_mask;
123    unsigned chunk_shift;
124
125    void *context;
126};
127
128/*
129 * Obtain the origin or cow device used by a given snapshot.
130 */
131struct dm_dev *dm_snap_origin(struct dm_snapshot *snap);
132struct dm_dev *dm_snap_cow(struct dm_snapshot *snap);
133
134/*
135 * Funtions to manipulate consecutive chunks
136 */
137# if defined(CONFIG_LBDAF) || (BITS_PER_LONG == 64)
138# define DM_CHUNK_CONSECUTIVE_BITS 8
139# define DM_CHUNK_NUMBER_BITS 56
140
141static inline chunk_t dm_chunk_number(chunk_t chunk)
142{
143    return chunk & (chunk_t)((1ULL << DM_CHUNK_NUMBER_BITS) - 1ULL);
144}
145
146static inline unsigned dm_consecutive_chunk_count(struct dm_exception *e)
147{
148    return e->new_chunk >> DM_CHUNK_NUMBER_BITS;
149}
150
151static inline void dm_consecutive_chunk_count_inc(struct dm_exception *e)
152{
153    e->new_chunk += (1ULL << DM_CHUNK_NUMBER_BITS);
154
155    BUG_ON(!dm_consecutive_chunk_count(e));
156}
157
158static inline void dm_consecutive_chunk_count_dec(struct dm_exception *e)
159{
160    BUG_ON(!dm_consecutive_chunk_count(e));
161
162    e->new_chunk -= (1ULL << DM_CHUNK_NUMBER_BITS);
163}
164
165# else
166# define DM_CHUNK_CONSECUTIVE_BITS 0
167
168static inline chunk_t dm_chunk_number(chunk_t chunk)
169{
170    return chunk;
171}
172
173static inline unsigned dm_consecutive_chunk_count(struct dm_exception *e)
174{
175    return 0;
176}
177
178static inline void dm_consecutive_chunk_count_inc(struct dm_exception *e)
179{
180}
181
182static inline void dm_consecutive_chunk_count_dec(struct dm_exception *e)
183{
184}
185
186# endif
187
188/*
189 * Return the number of sectors in the device.
190 */
191static inline sector_t get_dev_size(struct block_device *bdev)
192{
193    return i_size_read(bdev->bd_inode) >> SECTOR_SHIFT;
194}
195
196static inline chunk_t sector_to_chunk(struct dm_exception_store *store,
197                      sector_t sector)
198{
199    return sector >> store->chunk_shift;
200}
201
202int dm_exception_store_type_register(struct dm_exception_store_type *type);
203int dm_exception_store_type_unregister(struct dm_exception_store_type *type);
204
205int dm_exception_store_set_chunk_size(struct dm_exception_store *store,
206                      unsigned chunk_size,
207                      char **error);
208
209int dm_exception_store_create(struct dm_target *ti, int argc, char **argv,
210                  struct dm_snapshot *snap,
211                  unsigned *args_used,
212                  struct dm_exception_store **store);
213void dm_exception_store_destroy(struct dm_exception_store *store);
214
215int dm_exception_store_init(void);
216void dm_exception_store_exit(void);
217
218/*
219 * Two exception store implementations.
220 */
221int dm_persistent_snapshot_init(void);
222void dm_persistent_snapshot_exit(void);
223
224int dm_transient_snapshot_init(void);
225void dm_transient_snapshot_exit(void);
226
227#endif /* _LINUX_DM_EXCEPTION_STORE */
228

Archive Download this file

Branches:
ben-wpan
ben-wpan-stefan
javiroman/ks7010
jz-2.6.34
jz-2.6.34-rc5
jz-2.6.34-rc6
jz-2.6.34-rc7
jz-2.6.35
jz-2.6.36
jz-2.6.37
jz-2.6.38
jz-2.6.39
jz-3.0
jz-3.1
jz-3.11
jz-3.12
jz-3.13
jz-3.15
jz-3.16
jz-3.18-dt
jz-3.2
jz-3.3
jz-3.4
jz-3.5
jz-3.6
jz-3.6-rc2-pwm
jz-3.9
jz-3.9-clk
jz-3.9-rc8
jz47xx
jz47xx-2.6.38
master

Tags:
od-2011-09-04
od-2011-09-18
v2.6.34-rc5
v2.6.34-rc6
v2.6.34-rc7
v3.9



interactive