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1/* SPDX-License-Identifier: GPL-2.0-only */
2/*
3 * Copyright (C) 2001-2002 Sistina Software (UK) Limited.
4 * Copyright (C) 2008 Red Hat, Inc. All rights reserved.
5 *
6 * Device-mapper snapshot exception store.
7 *
8 * This file is released under the GPL.
9 */
10
11#ifndef _LINUX_DM_EXCEPTION_STORE
12#define _LINUX_DM_EXCEPTION_STORE
13
14#include <linux/blkdev.h>
15#include <linux/list_bl.h>
16#include <linux/device-mapper.h>
17
18/*
19 * The snapshot code deals with largish chunks of the disk at a
20 * time. Typically 32k - 512k.
21 */
22typedef sector_t chunk_t;
23
24/*
25 * An exception is used where an old chunk of data has been
26 * replaced by a new one.
27 * If chunk_t is 64 bits in size, the top 8 bits of new_chunk hold the number
28 * of chunks that follow contiguously. Remaining bits hold the number of the
29 * chunk within the device.
30 */
31struct dm_exception {
32 struct hlist_bl_node 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 dm_exception_store;
43struct dm_exception_store_type {
44 const char *name;
45 struct module *module;
46
47 int (*ctr)(struct dm_exception_store *store, char *options);
48
49 /*
50 * Destroys this object when you've finished with it.
51 */
52 void (*dtr)(struct dm_exception_store *store);
53
54 /*
55 * The target shouldn't read the COW device until this is
56 * called. As exceptions are read from the COW, they are
57 * reported back via the callback.
58 */
59 int (*read_metadata)(struct dm_exception_store *store,
60 int (*callback)(void *callback_context,
61 chunk_t old, chunk_t new),
62 void *callback_context);
63
64 /*
65 * Find somewhere to store the next exception.
66 */
67 int (*prepare_exception)(struct dm_exception_store *store,
68 struct dm_exception *e);
69
70 /*
71 * Update the metadata with this exception.
72 */
73 void (*commit_exception)(struct dm_exception_store *store,
74 struct dm_exception *e, int valid,
75 void (*callback)(void *, int success),
76 void *callback_context);
77
78 /*
79 * Returns 0 if the exception store is empty.
80 *
81 * If there are exceptions still to be merged, sets
82 * *last_old_chunk and *last_new_chunk to the most recent
83 * still-to-be-merged chunk and returns the number of
84 * consecutive previous ones.
85 */
86 int (*prepare_merge)(struct dm_exception_store *store,
87 chunk_t *last_old_chunk, chunk_t *last_new_chunk);
88
89 /*
90 * Clear the last n exceptions.
91 * nr_merged must be <= the value returned by prepare_merge.
92 */
93 int (*commit_merge)(struct dm_exception_store *store, int nr_merged);
94
95 /*
96 * The snapshot is invalid, note this in the metadata.
97 */
98 void (*drop_snapshot)(struct dm_exception_store *store);
99
100 unsigned int (*status)(struct dm_exception_store *store,
101 status_type_t status, char *result,
102 unsigned int maxlen);
103
104 /*
105 * Return how full the snapshot is.
106 */
107 void (*usage)(struct dm_exception_store *store,
108 sector_t *total_sectors, sector_t *sectors_allocated,
109 sector_t *metadata_sectors);
110
111 /* For internal device-mapper use only. */
112 struct list_head list;
113};
114
115struct dm_snapshot;
116
117struct dm_exception_store {
118 struct dm_exception_store_type *type;
119 struct dm_snapshot *snap;
120
121 /* Size of data blocks saved - must be a power of 2 */
122 unsigned int chunk_size;
123 unsigned int chunk_mask;
124 unsigned int chunk_shift;
125
126 void *context;
127
128 bool userspace_supports_overflow;
129};
130
131/*
132 * Obtain the origin or cow device used by a given snapshot.
133 */
134struct dm_dev *dm_snap_origin(struct dm_snapshot *snap);
135struct dm_dev *dm_snap_cow(struct dm_snapshot *snap);
136
137/*
138 * Funtions to manipulate consecutive chunks
139 */
140#define DM_CHUNK_CONSECUTIVE_BITS 8
141#define DM_CHUNK_NUMBER_BITS 56
142
143static inline chunk_t dm_chunk_number(chunk_t chunk)
144{
145 return chunk & (chunk_t)((1ULL << DM_CHUNK_NUMBER_BITS) - 1ULL);
146}
147
148static inline unsigned int dm_consecutive_chunk_count(struct dm_exception *e)
149{
150 return e->new_chunk >> DM_CHUNK_NUMBER_BITS;
151}
152
153static inline void dm_consecutive_chunk_count_inc(struct dm_exception *e)
154{
155 e->new_chunk += (1ULL << DM_CHUNK_NUMBER_BITS);
156
157 BUG_ON(!dm_consecutive_chunk_count(e));
158}
159
160static inline void dm_consecutive_chunk_count_dec(struct dm_exception *e)
161{
162 BUG_ON(!dm_consecutive_chunk_count(e));
163
164 e->new_chunk -= (1ULL << DM_CHUNK_NUMBER_BITS);
165}
166
167/*
168 * Return the number of sectors in the device.
169 */
170static inline sector_t get_dev_size(struct block_device *bdev)
171{
172 return bdev_nr_sectors(bdev);
173}
174
175static inline chunk_t sector_to_chunk(struct dm_exception_store *store,
176 sector_t sector)
177{
178 return sector >> store->chunk_shift;
179}
180
181int dm_exception_store_type_register(struct dm_exception_store_type *type);
182int dm_exception_store_type_unregister(struct dm_exception_store_type *type);
183
184int dm_exception_store_set_chunk_size(struct dm_exception_store *store,
185 unsigned int chunk_size,
186 char **error);
187
188int dm_exception_store_create(struct dm_target *ti, int argc, char **argv,
189 struct dm_snapshot *snap,
190 unsigned int *args_used,
191 struct dm_exception_store **store);
192void dm_exception_store_destroy(struct dm_exception_store *store);
193
194int dm_exception_store_init(void);
195void dm_exception_store_exit(void);
196
197/*
198 * Two exception store implementations.
199 */
200int dm_persistent_snapshot_init(void);
201void dm_persistent_snapshot_exit(void);
202
203int dm_transient_snapshot_init(void);
204void dm_transient_snapshot_exit(void);
205
206#endif /* _LINUX_DM_EXCEPTION_STORE */
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, char *options);
46
47 /*
48 * Destroys this object when you've finished with it.
49 */
50 void (*dtr) (struct dm_exception_store *store);
51
52 /*
53 * The target shouldn't read the COW device until this is
54 * called. As exceptions are read from the COW, they are
55 * reported back via the callback.
56 */
57 int (*read_metadata) (struct dm_exception_store *store,
58 int (*callback)(void *callback_context,
59 chunk_t old, chunk_t new),
60 void *callback_context);
61
62 /*
63 * Find somewhere to store the next exception.
64 */
65 int (*prepare_exception) (struct dm_exception_store *store,
66 struct dm_exception *e);
67
68 /*
69 * Update the metadata with this exception.
70 */
71 void (*commit_exception) (struct dm_exception_store *store,
72 struct dm_exception *e, int valid,
73 void (*callback) (void *, int success),
74 void *callback_context);
75
76 /*
77 * Returns 0 if the exception store is empty.
78 *
79 * If there are exceptions still to be merged, sets
80 * *last_old_chunk and *last_new_chunk to the most recent
81 * still-to-be-merged chunk and returns the number of
82 * consecutive previous ones.
83 */
84 int (*prepare_merge) (struct dm_exception_store *store,
85 chunk_t *last_old_chunk, chunk_t *last_new_chunk);
86
87 /*
88 * Clear the last n exceptions.
89 * nr_merged must be <= the value returned by prepare_merge.
90 */
91 int (*commit_merge) (struct dm_exception_store *store, int nr_merged);
92
93 /*
94 * The snapshot is invalid, note this in the metadata.
95 */
96 void (*drop_snapshot) (struct dm_exception_store *store);
97
98 unsigned (*status) (struct dm_exception_store *store,
99 status_type_t status, char *result,
100 unsigned maxlen);
101
102 /*
103 * Return how full the snapshot is.
104 */
105 void (*usage) (struct dm_exception_store *store,
106 sector_t *total_sectors, sector_t *sectors_allocated,
107 sector_t *metadata_sectors);
108
109 /* For internal device-mapper use only. */
110 struct list_head list;
111};
112
113struct dm_snapshot;
114
115struct dm_exception_store {
116 struct dm_exception_store_type *type;
117 struct dm_snapshot *snap;
118
119 /* Size of data blocks saved - must be a power of 2 */
120 unsigned chunk_size;
121 unsigned chunk_mask;
122 unsigned chunk_shift;
123
124 void *context;
125
126 bool userspace_supports_overflow;
127};
128
129/*
130 * Obtain the origin or cow device used by a given snapshot.
131 */
132struct dm_dev *dm_snap_origin(struct dm_snapshot *snap);
133struct dm_dev *dm_snap_cow(struct dm_snapshot *snap);
134
135/*
136 * Funtions to manipulate consecutive chunks
137 */
138# if defined(CONFIG_LBDAF) || (BITS_PER_LONG == 64)
139# define DM_CHUNK_CONSECUTIVE_BITS 8
140# define DM_CHUNK_NUMBER_BITS 56
141
142static inline chunk_t dm_chunk_number(chunk_t chunk)
143{
144 return chunk & (chunk_t)((1ULL << DM_CHUNK_NUMBER_BITS) - 1ULL);
145}
146
147static inline unsigned dm_consecutive_chunk_count(struct dm_exception *e)
148{
149 return e->new_chunk >> DM_CHUNK_NUMBER_BITS;
150}
151
152static inline void dm_consecutive_chunk_count_inc(struct dm_exception *e)
153{
154 e->new_chunk += (1ULL << DM_CHUNK_NUMBER_BITS);
155
156 BUG_ON(!dm_consecutive_chunk_count(e));
157}
158
159static inline void dm_consecutive_chunk_count_dec(struct dm_exception *e)
160{
161 BUG_ON(!dm_consecutive_chunk_count(e));
162
163 e->new_chunk -= (1ULL << DM_CHUNK_NUMBER_BITS);
164}
165
166# else
167# define DM_CHUNK_CONSECUTIVE_BITS 0
168
169static inline chunk_t dm_chunk_number(chunk_t chunk)
170{
171 return chunk;
172}
173
174static inline unsigned dm_consecutive_chunk_count(struct dm_exception *e)
175{
176 return 0;
177}
178
179static inline void dm_consecutive_chunk_count_inc(struct dm_exception *e)
180{
181}
182
183static inline void dm_consecutive_chunk_count_dec(struct dm_exception *e)
184{
185}
186
187# endif
188
189/*
190 * Return the number of sectors in the device.
191 */
192static inline sector_t get_dev_size(struct block_device *bdev)
193{
194 return i_size_read(bdev->bd_inode) >> SECTOR_SHIFT;
195}
196
197static inline chunk_t sector_to_chunk(struct dm_exception_store *store,
198 sector_t sector)
199{
200 return sector >> store->chunk_shift;
201}
202
203int dm_exception_store_type_register(struct dm_exception_store_type *type);
204int dm_exception_store_type_unregister(struct dm_exception_store_type *type);
205
206int dm_exception_store_set_chunk_size(struct dm_exception_store *store,
207 unsigned chunk_size,
208 char **error);
209
210int dm_exception_store_create(struct dm_target *ti, int argc, char **argv,
211 struct dm_snapshot *snap,
212 unsigned *args_used,
213 struct dm_exception_store **store);
214void dm_exception_store_destroy(struct dm_exception_store *store);
215
216int dm_exception_store_init(void);
217void dm_exception_store_exit(void);
218
219/*
220 * Two exception store implementations.
221 */
222int dm_persistent_snapshot_init(void);
223void dm_persistent_snapshot_exit(void);
224
225int dm_transient_snapshot_init(void);
226void dm_transient_snapshot_exit(void);
227
228#endif /* _LINUX_DM_EXCEPTION_STORE */