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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/list_bl.h>
15#include <linux/device-mapper.h>
16
17/*
18 * The snapshot code deals with largish chunks of the disk at a
19 * time. Typically 32k - 512k.
20 */
21typedef sector_t chunk_t;
22
23/*
24 * An exception is used where an old chunk of data has been
25 * replaced by a new one.
26 * If chunk_t is 64 bits in size, the top 8 bits of new_chunk hold the number
27 * of chunks that follow contiguously. Remaining bits hold the number of the
28 * chunk within the device.
29 */
30struct dm_exception {
31 struct hlist_bl_node hash_list;
32
33 chunk_t old_chunk;
34 chunk_t new_chunk;
35};
36
37/*
38 * Abstraction to handle the meta/layout of exception stores (the
39 * COW device).
40 */
41struct dm_exception_store;
42struct dm_exception_store_type {
43 const char *name;
44 struct module *module;
45
46 int (*ctr) (struct dm_exception_store *store, char *options);
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, int valid,
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 bool userspace_supports_overflow;
128};
129
130/*
131 * Obtain the origin or cow device used by a given snapshot.
132 */
133struct dm_dev *dm_snap_origin(struct dm_snapshot *snap);
134struct dm_dev *dm_snap_cow(struct dm_snapshot *snap);
135
136/*
137 * Funtions to manipulate consecutive chunks
138 */
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/*
167 * Return the number of sectors in the device.
168 */
169static inline sector_t get_dev_size(struct block_device *bdev)
170{
171 return bdev_nr_sectors(bdev);
172}
173
174static inline chunk_t sector_to_chunk(struct dm_exception_store *store,
175 sector_t sector)
176{
177 return sector >> store->chunk_shift;
178}
179
180int dm_exception_store_type_register(struct dm_exception_store_type *type);
181int dm_exception_store_type_unregister(struct dm_exception_store_type *type);
182
183int dm_exception_store_set_chunk_size(struct dm_exception_store *store,
184 unsigned chunk_size,
185 char **error);
186
187int dm_exception_store_create(struct dm_target *ti, int argc, char **argv,
188 struct dm_snapshot *snap,
189 unsigned *args_used,
190 struct dm_exception_store **store);
191void dm_exception_store_destroy(struct dm_exception_store *store);
192
193int dm_exception_store_init(void);
194void dm_exception_store_exit(void);
195
196/*
197 * Two exception store implementations.
198 */
199int dm_persistent_snapshot_init(void);
200void dm_persistent_snapshot_exit(void);
201
202int dm_transient_snapshot_init(void);
203void dm_transient_snapshot_exit(void);
204
205#endif /* _LINUX_DM_EXCEPTION_STORE */
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 */