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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 */
29struct dm_snap_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 */
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,
Jonathan Brassowaea53d92009-01-06 03:05:15 +000067 struct dm_snap_exception *e);
68
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,
Jonathan Brassowaea53d92009-01-06 03:05:15 +000073 struct dm_snap_exception *e,
74 void (*callback) (void *, int success),
75 void *callback_context);
76
77 /*
78 * The snapshot is invalid, note this in the metadata.
79 */
Jonathan Brassow1ae25f92009-01-06 03:05:16 +000080 void (*drop_snapshot) (struct dm_exception_store *store);
Jonathan Brassowaea53d92009-01-06 03:05:15 +000081
Jonathan Brassow1e302a92009-04-02 19:55:35 +010082 unsigned (*status) (struct dm_exception_store *store,
83 status_type_t status, char *result,
84 unsigned maxlen);
Jonathan Brassowa159c1a2009-01-06 03:05:19 +000085
Jonathan Brassowaea53d92009-01-06 03:05:15 +000086 /*
87 * Return how full the snapshot is.
88 */
Jonathan Brassow1ae25f92009-01-06 03:05:16 +000089 void (*fraction_full) (struct dm_exception_store *store,
Jonathan Brassowaea53d92009-01-06 03:05:15 +000090 sector_t *numerator,
91 sector_t *denominator);
Jonathan Brassow493df712009-04-02 19:55:31 +010092
93 /* For internal device-mapper use only. */
94 struct list_head list;
Jonathan Brassowb2a11462009-04-02 19:55:30 +010095};
96
97struct dm_exception_store {
Jonathan Brassow493df712009-04-02 19:55:31 +010098 struct dm_exception_store_type *type;
Jonathan Brassow0cea9c72009-04-02 19:55:32 +010099 struct dm_target *ti;
Jonathan Brassowaea53d92009-01-06 03:05:15 +0000100
Jonathan Brassow49beb2b2009-04-02 19:55:33 +0100101 struct dm_dev *cow;
102
Jonathan Brassowd0216842009-04-02 19:55:32 +0100103 /* Size of data blocks saved - must be a power of 2 */
104 chunk_t chunk_size;
105 chunk_t chunk_mask;
106 chunk_t chunk_shift;
107
Jonathan Brassowaea53d92009-01-06 03:05:15 +0000108 void *context;
109};
110
111/*
112 * Funtions to manipulate consecutive chunks
113 */
Bartlomiej Zolnierkiewicz90c699a2009-06-19 08:08:50 +0200114# if defined(CONFIG_LBDAF) || (BITS_PER_LONG == 64)
Jonathan Brassowaea53d92009-01-06 03:05:15 +0000115# define DM_CHUNK_CONSECUTIVE_BITS 8
116# define DM_CHUNK_NUMBER_BITS 56
117
118static inline chunk_t dm_chunk_number(chunk_t chunk)
119{
120 return chunk & (chunk_t)((1ULL << DM_CHUNK_NUMBER_BITS) - 1ULL);
121}
122
123static inline unsigned dm_consecutive_chunk_count(struct dm_snap_exception *e)
124{
125 return e->new_chunk >> DM_CHUNK_NUMBER_BITS;
126}
127
128static inline void dm_consecutive_chunk_count_inc(struct dm_snap_exception *e)
129{
130 e->new_chunk += (1ULL << DM_CHUNK_NUMBER_BITS);
131
132 BUG_ON(!dm_consecutive_chunk_count(e));
133}
134
135# else
136# define DM_CHUNK_CONSECUTIVE_BITS 0
137
138static inline chunk_t dm_chunk_number(chunk_t chunk)
139{
140 return chunk;
141}
142
143static inline unsigned dm_consecutive_chunk_count(struct dm_snap_exception *e)
144{
145 return 0;
146}
147
148static inline void dm_consecutive_chunk_count_inc(struct dm_snap_exception *e)
149{
150}
151
152# endif
153
Jonathan Brassow71fab002009-04-02 19:55:33 +0100154/*
155 * Return the number of sectors in the device.
156 */
157static inline sector_t get_dev_size(struct block_device *bdev)
158{
Mikulas Patocka5657e8f2009-06-22 10:12:14 +0100159 return i_size_read(bdev->bd_inode) >> SECTOR_SHIFT;
Jonathan Brassow71fab002009-04-02 19:55:33 +0100160}
161
162static inline chunk_t sector_to_chunk(struct dm_exception_store *store,
163 sector_t sector)
164{
165 return (sector & ~store->chunk_mask) >> store->chunk_shift;
166}
167
Jonathan Brassow493df712009-04-02 19:55:31 +0100168int dm_exception_store_type_register(struct dm_exception_store_type *type);
169int dm_exception_store_type_unregister(struct dm_exception_store_type *type);
170
Jonathan Brassowfee19982009-04-02 19:55:34 +0100171int dm_exception_store_create(struct dm_target *ti, int argc, char **argv,
172 unsigned *args_used,
Jonathan Brassow493df712009-04-02 19:55:31 +0100173 struct dm_exception_store **store);
174void dm_exception_store_destroy(struct dm_exception_store *store);
175
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000176int dm_exception_store_init(void);
177void dm_exception_store_exit(void);
178
Jonathan Brassowaea53d92009-01-06 03:05:15 +0000179/*
180 * Two exception store implementations.
181 */
Alasdair G Kergon4db6bfe2009-01-06 03:05:17 +0000182int dm_persistent_snapshot_init(void);
183void dm_persistent_snapshot_exit(void);
184
185int dm_transient_snapshot_init(void);
186void dm_transient_snapshot_exit(void);
187
Jonathan Brassowaea53d92009-01-06 03:05:15 +0000188#endif /* _LINUX_DM_EXCEPTION_STORE */