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Jonathan Brassowaea53d92009-01-06 03:05:15 +00001/*
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>
Jonathan Brassowa159c1a2009-01-06 03:05:19 +000014#include <linux/device-mapper.h>
Jonathan Brassowaea53d92009-01-06 03:05:15 +000015
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 */
Jon Brassow1d4989c2009-12-10 23:52:10 +000029struct dm_exception {
Jonathan Brassowaea53d92009-01-06 03:05:15 +000030 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 */
Jonathan Brassowb2a11462009-04-02 19:55:30 +010040struct dm_exception_store;
41struct dm_exception_store_type {
Jonathan Brassow493df712009-04-02 19:55:31 +010042 const char *name;
43 struct module *module;
44
Mike Snitzerb0d3cc02015-10-08 18:05:41 -040045 int (*ctr) (struct dm_exception_store *store, char *options);
Jonathan Brassowb2a11462009-04-02 19:55:30 +010046
Jonathan Brassowaea53d92009-01-06 03:05:15 +000047 /*
48 * Destroys this object when you've finished with it.
49 */
Jonathan Brassowb2a11462009-04-02 19:55:30 +010050 void (*dtr) (struct dm_exception_store *store);
Jonathan Brassowaea53d92009-01-06 03:05:15 +000051
52 /*
53 * The target shouldn't read the COW device until this is
Jonathan Brassowa159c1a2009-01-06 03:05:19 +000054 * called. As exceptions are read from the COW, they are
55 * reported back via the callback.
Jonathan Brassowaea53d92009-01-06 03:05:15 +000056 */
Jonathan Brassowa159c1a2009-01-06 03:05:19 +000057 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);
Jonathan Brassowaea53d92009-01-06 03:05:15 +000061
62 /*
63 * Find somewhere to store the next exception.
64 */
Jonathan Brassow1ae25f92009-01-06 03:05:16 +000065 int (*prepare_exception) (struct dm_exception_store *store,
Jon Brassow1d4989c2009-12-10 23:52:10 +000066 struct dm_exception *e);
Jonathan Brassowaea53d92009-01-06 03:05:15 +000067
68 /*
69 * Update the metadata with this exception.
70 */
Jonathan Brassow1ae25f92009-01-06 03:05:16 +000071 void (*commit_exception) (struct dm_exception_store *store,
Jon Brassow1d4989c2009-12-10 23:52:10 +000072 struct dm_exception *e,
Jonathan Brassowaea53d92009-01-06 03:05:15 +000073 void (*callback) (void *, int success),
74 void *callback_context);
75
76 /*
Mikulas Patocka4454a622009-12-10 23:52:29 +000077 * 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 /*
Jonathan Brassowaea53d92009-01-06 03:05:15 +000094 * The snapshot is invalid, note this in the metadata.
95 */
Jonathan Brassow1ae25f92009-01-06 03:05:16 +000096 void (*drop_snapshot) (struct dm_exception_store *store);
Jonathan Brassowaea53d92009-01-06 03:05:15 +000097
Jonathan Brassow1e302a92009-04-02 19:55:35 +010098 unsigned (*status) (struct dm_exception_store *store,
99 status_type_t status, char *result,
100 unsigned maxlen);
Jonathan Brassowa159c1a2009-01-06 03:05:19 +0000101
Jonathan Brassowaea53d92009-01-06 03:05:15 +0000102 /*
103 * Return how full the snapshot is.
104 */
Mike Snitzer985903b2009-12-10 23:52:11 +0000105 void (*usage) (struct dm_exception_store *store,
106 sector_t *total_sectors, sector_t *sectors_allocated,
107 sector_t *metadata_sectors);
Jonathan Brassow493df712009-04-02 19:55:31 +0100108
109 /* For internal device-mapper use only. */
110 struct list_head list;
Jonathan Brassowb2a11462009-04-02 19:55:30 +0100111};
112
Mike Snitzerfc56f6f2009-12-10 23:52:12 +0000113struct dm_snapshot;
114
Jonathan Brassowb2a11462009-04-02 19:55:30 +0100115struct dm_exception_store {
Jonathan Brassow493df712009-04-02 19:55:31 +0100116 struct dm_exception_store_type *type;
Mike Snitzerfc56f6f2009-12-10 23:52:12 +0000117 struct dm_snapshot *snap;
Jonathan Brassow49beb2b2009-04-02 19:55:33 +0100118
Jonathan Brassowd0216842009-04-02 19:55:32 +0100119 /* Size of data blocks saved - must be a power of 2 */
Mikulas Patockadf96eee2009-10-16 23:18:17 +0100120 unsigned chunk_size;
121 unsigned chunk_mask;
122 unsigned chunk_shift;
Jonathan Brassowd0216842009-04-02 19:55:32 +0100123
Jonathan Brassowaea53d92009-01-06 03:05:15 +0000124 void *context;
Mike Snitzerb0d3cc02015-10-08 18:05:41 -0400125
126 bool userspace_supports_overflow;
Jonathan Brassowaea53d92009-01-06 03:05:15 +0000127};
128
129/*
Mikulas Patockac2411042010-08-12 04:13:51 +0100130 * Obtain the origin or cow device used by a given snapshot.
Mike Snitzerfc56f6f2009-12-10 23:52:12 +0000131 */
Mikulas Patockac2411042010-08-12 04:13:51 +0100132struct dm_dev *dm_snap_origin(struct dm_snapshot *snap);
Mike Snitzerfc56f6f2009-12-10 23:52:12 +0000133struct dm_dev *dm_snap_cow(struct dm_snapshot *snap);
134
135/*
Jonathan Brassowaea53d92009-01-06 03:05:15 +0000136 * Funtions to manipulate consecutive chunks
137 */
Bartlomiej Zolnierkiewicz90c699a2009-06-19 08:08:50 +0200138# if defined(CONFIG_LBDAF) || (BITS_PER_LONG == 64)
Jonathan Brassowaea53d92009-01-06 03:05:15 +0000139# 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
Jon Brassow1d4989c2009-12-10 23:52:10 +0000147static inline unsigned dm_consecutive_chunk_count(struct dm_exception *e)
Jonathan Brassowaea53d92009-01-06 03:05:15 +0000148{
149 return e->new_chunk >> DM_CHUNK_NUMBER_BITS;
150}
151
Jon Brassow1d4989c2009-12-10 23:52:10 +0000152static inline void dm_consecutive_chunk_count_inc(struct dm_exception *e)
Jonathan Brassowaea53d92009-01-06 03:05:15 +0000153{
154 e->new_chunk += (1ULL << DM_CHUNK_NUMBER_BITS);
155
156 BUG_ON(!dm_consecutive_chunk_count(e));
157}
158
Mikulas Patocka1e03f972009-12-10 23:52:32 +0000159static 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
Jonathan Brassowaea53d92009-01-06 03:05:15 +0000166# 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
Jon Brassow1d4989c2009-12-10 23:52:10 +0000174static inline unsigned dm_consecutive_chunk_count(struct dm_exception *e)
Jonathan Brassowaea53d92009-01-06 03:05:15 +0000175{
176 return 0;
177}
178
Jon Brassow1d4989c2009-12-10 23:52:10 +0000179static inline void dm_consecutive_chunk_count_inc(struct dm_exception *e)
Jonathan Brassowaea53d92009-01-06 03:05:15 +0000180{
181}
182
Mikulas Patocka1e03f972009-12-10 23:52:32 +0000183static inline void dm_consecutive_chunk_count_dec(struct dm_exception *e)
184{
185}
186
Jonathan Brassowaea53d92009-01-06 03:05:15 +0000187# endif
188
Jonathan Brassow71fab002009-04-02 19:55:33 +0100189/*
190 * Return the number of sectors in the device.
191 */
192static inline sector_t get_dev_size(struct block_device *bdev)
193{
Mikulas Patocka5657e8f2009-06-22 10:12:14 +0100194 return i_size_read(bdev->bd_inode) >> SECTOR_SHIFT;
Jonathan Brassow71fab002009-04-02 19:55:33 +0100195}
196
197static inline chunk_t sector_to_chunk(struct dm_exception_store *store,
198 sector_t sector)
199{
Mikulas Patocka102c6dd2009-12-10 23:52:08 +0000200 return sector >> store->chunk_shift;
Jonathan Brassow71fab002009-04-02 19:55:33 +0100201}
202
Jonathan Brassow493df712009-04-02 19:55:31 +0100203int dm_exception_store_type_register(struct dm_exception_store_type *type);
204int dm_exception_store_type_unregister(struct dm_exception_store_type *type);
205
Mikulas Patocka2defcc32009-09-04 20:40:41 +0100206int dm_exception_store_set_chunk_size(struct dm_exception_store *store,
Mikulas Patockadf96eee2009-10-16 23:18:17 +0100207 unsigned chunk_size,
Mikulas Patocka2defcc32009-09-04 20:40:41 +0100208 char **error);
209
Jonathan Brassowfee19982009-04-02 19:55:34 +0100210int dm_exception_store_create(struct dm_target *ti, int argc, char **argv,
Mike Snitzerfc56f6f2009-12-10 23:52:12 +0000211 struct dm_snapshot *snap,
Jonathan Brassowfee19982009-04-02 19:55:34 +0100212 unsigned *args_used,
Jonathan Brassow493df712009-04-02 19:55:31 +0100213 struct dm_exception_store **store);
214void dm_exception_store_destroy(struct dm_exception_store *store);
215
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000216int dm_exception_store_init(void);
217void dm_exception_store_exit(void);
218
Jonathan Brassowaea53d92009-01-06 03:05:15 +0000219/*
220 * Two exception store implementations.
221 */
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000222int 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
Jonathan Brassowaea53d92009-01-06 03:05:15 +0000228#endif /* _LINUX_DM_EXCEPTION_STORE */