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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
Jonathan Brassowb2a11462009-04-02 19:55:30 +010045 int (*ctr) (struct dm_exception_store *store,
46 unsigned argc, char **argv);
47
Jonathan Brassowaea53d92009-01-06 03:05:15 +000048 /*
49 * Destroys this object when you've finished with it.
50 */
Jonathan Brassowb2a11462009-04-02 19:55:30 +010051 void (*dtr) (struct dm_exception_store *store);
Jonathan Brassowaea53d92009-01-06 03:05:15 +000052
53 /*
54 * The target shouldn't read the COW device until this is
Jonathan Brassowa159c1a2009-01-06 03:05:19 +000055 * called. As exceptions are read from the COW, they are
56 * reported back via the callback.
Jonathan Brassowaea53d92009-01-06 03:05:15 +000057 */
Jonathan Brassowa159c1a2009-01-06 03:05:19 +000058 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);
Jonathan Brassowaea53d92009-01-06 03:05:15 +000062
63 /*
64 * Find somewhere to store the next exception.
65 */
Jonathan Brassow1ae25f92009-01-06 03:05:16 +000066 int (*prepare_exception) (struct dm_exception_store *store,
Jon Brassow1d4989c2009-12-10 23:52:10 +000067 struct dm_exception *e);
Jonathan Brassowaea53d92009-01-06 03:05:15 +000068
69 /*
70 * Update the metadata with this exception.
71 */
Jonathan Brassow1ae25f92009-01-06 03:05:16 +000072 void (*commit_exception) (struct dm_exception_store *store,
Jon Brassow1d4989c2009-12-10 23:52:10 +000073 struct dm_exception *e,
Jonathan Brassowaea53d92009-01-06 03:05:15 +000074 void (*callback) (void *, int success),
75 void *callback_context);
76
77 /*
Mikulas Patocka4454a622009-12-10 23:52:29 +000078 * 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 /*
Jonathan Brassowaea53d92009-01-06 03:05:15 +000095 * The snapshot is invalid, note this in the metadata.
96 */
Jonathan Brassow1ae25f92009-01-06 03:05:16 +000097 void (*drop_snapshot) (struct dm_exception_store *store);
Jonathan Brassowaea53d92009-01-06 03:05:15 +000098
Jonathan Brassow1e302a92009-04-02 19:55:35 +010099 unsigned (*status) (struct dm_exception_store *store,
100 status_type_t status, char *result,
101 unsigned maxlen);
Jonathan Brassowa159c1a2009-01-06 03:05:19 +0000102
Jonathan Brassowaea53d92009-01-06 03:05:15 +0000103 /*
104 * Return how full the snapshot is.
105 */
Mike Snitzer985903b2009-12-10 23:52:11 +0000106 void (*usage) (struct dm_exception_store *store,
107 sector_t *total_sectors, sector_t *sectors_allocated,
108 sector_t *metadata_sectors);
Jonathan Brassow493df712009-04-02 19:55:31 +0100109
110 /* For internal device-mapper use only. */
111 struct list_head list;
Jonathan Brassowb2a11462009-04-02 19:55:30 +0100112};
113
Mike Snitzerfc56f6f2009-12-10 23:52:12 +0000114struct dm_snapshot;
115
Jonathan Brassowb2a11462009-04-02 19:55:30 +0100116struct dm_exception_store {
Jonathan Brassow493df712009-04-02 19:55:31 +0100117 struct dm_exception_store_type *type;
Mike Snitzerfc56f6f2009-12-10 23:52:12 +0000118 struct dm_snapshot *snap;
Jonathan Brassow49beb2b2009-04-02 19:55:33 +0100119
Jonathan Brassowd0216842009-04-02 19:55:32 +0100120 /* Size of data blocks saved - must be a power of 2 */
Mikulas Patockadf96eee2009-10-16 23:18:17 +0100121 unsigned chunk_size;
122 unsigned chunk_mask;
123 unsigned chunk_shift;
Jonathan Brassowd0216842009-04-02 19:55:32 +0100124
Jonathan Brassowaea53d92009-01-06 03:05:15 +0000125 void *context;
126};
127
128/*
Mike Snitzerfc56f6f2009-12-10 23:52:12 +0000129 * Obtain the cow device used by a given snapshot.
130 */
131struct dm_dev *dm_snap_cow(struct dm_snapshot *snap);
132
133/*
Jonathan Brassowaea53d92009-01-06 03:05:15 +0000134 * Funtions to manipulate consecutive chunks
135 */
Bartlomiej Zolnierkiewicz90c699a2009-06-19 08:08:50 +0200136# if defined(CONFIG_LBDAF) || (BITS_PER_LONG == 64)
Jonathan Brassowaea53d92009-01-06 03:05:15 +0000137# define DM_CHUNK_CONSECUTIVE_BITS 8
138# define DM_CHUNK_NUMBER_BITS 56
139
140static inline chunk_t dm_chunk_number(chunk_t chunk)
141{
142 return chunk & (chunk_t)((1ULL << DM_CHUNK_NUMBER_BITS) - 1ULL);
143}
144
Jon Brassow1d4989c2009-12-10 23:52:10 +0000145static inline unsigned dm_consecutive_chunk_count(struct dm_exception *e)
Jonathan Brassowaea53d92009-01-06 03:05:15 +0000146{
147 return e->new_chunk >> DM_CHUNK_NUMBER_BITS;
148}
149
Jon Brassow1d4989c2009-12-10 23:52:10 +0000150static inline void dm_consecutive_chunk_count_inc(struct dm_exception *e)
Jonathan Brassowaea53d92009-01-06 03:05:15 +0000151{
152 e->new_chunk += (1ULL << DM_CHUNK_NUMBER_BITS);
153
154 BUG_ON(!dm_consecutive_chunk_count(e));
155}
156
Mikulas Patocka1e03f972009-12-10 23:52:32 +0000157static inline void dm_consecutive_chunk_count_dec(struct dm_exception *e)
158{
159 BUG_ON(!dm_consecutive_chunk_count(e));
160
161 e->new_chunk -= (1ULL << DM_CHUNK_NUMBER_BITS);
162}
163
Jonathan Brassowaea53d92009-01-06 03:05:15 +0000164# else
165# define DM_CHUNK_CONSECUTIVE_BITS 0
166
167static inline chunk_t dm_chunk_number(chunk_t chunk)
168{
169 return chunk;
170}
171
Jon Brassow1d4989c2009-12-10 23:52:10 +0000172static inline unsigned dm_consecutive_chunk_count(struct dm_exception *e)
Jonathan Brassowaea53d92009-01-06 03:05:15 +0000173{
174 return 0;
175}
176
Jon Brassow1d4989c2009-12-10 23:52:10 +0000177static inline void dm_consecutive_chunk_count_inc(struct dm_exception *e)
Jonathan Brassowaea53d92009-01-06 03:05:15 +0000178{
179}
180
Mikulas Patocka1e03f972009-12-10 23:52:32 +0000181static inline void dm_consecutive_chunk_count_dec(struct dm_exception *e)
182{
183}
184
Jonathan Brassowaea53d92009-01-06 03:05:15 +0000185# endif
186
Jonathan Brassow71fab002009-04-02 19:55:33 +0100187/*
188 * Return the number of sectors in the device.
189 */
190static inline sector_t get_dev_size(struct block_device *bdev)
191{
Mikulas Patocka5657e8f2009-06-22 10:12:14 +0100192 return i_size_read(bdev->bd_inode) >> SECTOR_SHIFT;
Jonathan Brassow71fab002009-04-02 19:55:33 +0100193}
194
195static inline chunk_t sector_to_chunk(struct dm_exception_store *store,
196 sector_t sector)
197{
Mikulas Patocka102c6dd2009-12-10 23:52:08 +0000198 return sector >> store->chunk_shift;
Jonathan Brassow71fab002009-04-02 19:55:33 +0100199}
200
Jonathan Brassow493df712009-04-02 19:55:31 +0100201int dm_exception_store_type_register(struct dm_exception_store_type *type);
202int dm_exception_store_type_unregister(struct dm_exception_store_type *type);
203
Mikulas Patocka2defcc32009-09-04 20:40:41 +0100204int dm_exception_store_set_chunk_size(struct dm_exception_store *store,
Mikulas Patockadf96eee2009-10-16 23:18:17 +0100205 unsigned chunk_size,
Mikulas Patocka2defcc32009-09-04 20:40:41 +0100206 char **error);
207
Jonathan Brassowfee19982009-04-02 19:55:34 +0100208int dm_exception_store_create(struct dm_target *ti, int argc, char **argv,
Mike Snitzerfc56f6f2009-12-10 23:52:12 +0000209 struct dm_snapshot *snap,
Jonathan Brassowfee19982009-04-02 19:55:34 +0100210 unsigned *args_used,
Jonathan Brassow493df712009-04-02 19:55:31 +0100211 struct dm_exception_store **store);
212void dm_exception_store_destroy(struct dm_exception_store *store);
213
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000214int dm_exception_store_init(void);
215void dm_exception_store_exit(void);
216
Jonathan Brassowaea53d92009-01-06 03:05:15 +0000217/*
218 * Two exception store implementations.
219 */
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000220int dm_persistent_snapshot_init(void);
221void dm_persistent_snapshot_exit(void);
222
223int dm_transient_snapshot_init(void);
224void dm_transient_snapshot_exit(void);
225
Jonathan Brassowaea53d92009-01-06 03:05:15 +0000226#endif /* _LINUX_DM_EXCEPTION_STORE */