2 * Copyright (C) 2001-2002 Sistina Software (UK) Limited.
3 * Copyright (C) 2008 Red Hat, Inc. All rights reserved.
5 * Device-mapper snapshot exception store.
7 * This file is released under the GPL.
10 #ifndef _LINUX_DM_EXCEPTION_STORE
11 #define _LINUX_DM_EXCEPTION_STORE
13 #include <linux/blkdev.h>
14 #include <linux/device-mapper.h>
17 * The snapshot code deals with largish chunks of the disk at a
18 * time. Typically 32k - 512k.
20 typedef sector_t chunk_t
;
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.
30 struct list_head hash_list
;
37 * Abstraction to handle the meta/layout of exception stores (the
40 struct dm_exception_store
;
41 struct dm_exception_store_type
{
43 struct module
*module
;
45 int (*ctr
) (struct dm_exception_store
*store
,
46 unsigned argc
, char **argv
);
49 * Destroys this object when you've finished with it.
51 void (*dtr
) (struct dm_exception_store
*store
);
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.
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
);
64 * Find somewhere to store the next exception.
66 int (*prepare_exception
) (struct dm_exception_store
*store
,
67 struct dm_exception
*e
);
70 * Update the metadata with this exception.
72 void (*commit_exception
) (struct dm_exception_store
*store
,
73 struct dm_exception
*e
,
74 void (*callback
) (void *, int success
),
75 void *callback_context
);
78 * Returns 0 if the exception store is empty.
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.
85 int (*prepare_merge
) (struct dm_exception_store
*store
,
86 chunk_t
*last_old_chunk
, chunk_t
*last_new_chunk
);
89 * Clear the last n exceptions.
90 * nr_merged must be <= the value returned by prepare_merge.
92 int (*commit_merge
) (struct dm_exception_store
*store
, int nr_merged
);
95 * The snapshot is invalid, note this in the metadata.
97 void (*drop_snapshot
) (struct dm_exception_store
*store
);
99 unsigned (*status
) (struct dm_exception_store
*store
,
100 status_type_t status
, char *result
,
104 * Return how full the snapshot is.
106 void (*usage
) (struct dm_exception_store
*store
,
107 sector_t
*total_sectors
, sector_t
*sectors_allocated
,
108 sector_t
*metadata_sectors
);
110 /* For internal device-mapper use only. */
111 struct list_head list
;
116 struct dm_exception_store
{
117 struct dm_exception_store_type
*type
;
118 struct dm_snapshot
*snap
;
120 /* Size of data blocks saved - must be a power of 2 */
123 unsigned chunk_shift
;
129 * Obtain the origin or cow device used by a given snapshot.
131 struct dm_dev
*dm_snap_origin(struct dm_snapshot
*snap
);
132 struct dm_dev
*dm_snap_cow(struct dm_snapshot
*snap
);
135 * Funtions to manipulate consecutive chunks
137 # if defined(CONFIG_LBDAF) || (BITS_PER_LONG == 64)
138 # define DM_CHUNK_CONSECUTIVE_BITS 8
139 # define DM_CHUNK_NUMBER_BITS 56
141 static inline chunk_t
dm_chunk_number(chunk_t chunk
)
143 return chunk
& (chunk_t
)((1ULL << DM_CHUNK_NUMBER_BITS
) - 1ULL);
146 static inline unsigned dm_consecutive_chunk_count(struct dm_exception
*e
)
148 return e
->new_chunk
>> DM_CHUNK_NUMBER_BITS
;
151 static inline void dm_consecutive_chunk_count_inc(struct dm_exception
*e
)
153 e
->new_chunk
+= (1ULL << DM_CHUNK_NUMBER_BITS
);
155 BUG_ON(!dm_consecutive_chunk_count(e
));
158 static inline void dm_consecutive_chunk_count_dec(struct dm_exception
*e
)
160 BUG_ON(!dm_consecutive_chunk_count(e
));
162 e
->new_chunk
-= (1ULL << DM_CHUNK_NUMBER_BITS
);
166 # define DM_CHUNK_CONSECUTIVE_BITS 0
168 static inline chunk_t
dm_chunk_number(chunk_t chunk
)
173 static inline unsigned dm_consecutive_chunk_count(struct dm_exception
*e
)
178 static inline void dm_consecutive_chunk_count_inc(struct dm_exception
*e
)
182 static inline void dm_consecutive_chunk_count_dec(struct dm_exception
*e
)
189 * Return the number of sectors in the device.
191 static inline sector_t
get_dev_size(struct block_device
*bdev
)
193 return i_size_read(bdev
->bd_inode
) >> SECTOR_SHIFT
;
196 static inline chunk_t
sector_to_chunk(struct dm_exception_store
*store
,
199 return sector
>> store
->chunk_shift
;
202 int dm_exception_store_type_register(struct dm_exception_store_type
*type
);
203 int dm_exception_store_type_unregister(struct dm_exception_store_type
*type
);
205 int dm_exception_store_set_chunk_size(struct dm_exception_store
*store
,
209 int dm_exception_store_create(struct dm_target
*ti
, int argc
, char **argv
,
210 struct dm_snapshot
*snap
,
212 struct dm_exception_store
**store
);
213 void dm_exception_store_destroy(struct dm_exception_store
*store
);
215 int dm_exception_store_init(void);
216 void dm_exception_store_exit(void);
219 * Two exception store implementations.
221 int dm_persistent_snapshot_init(void);
222 void dm_persistent_snapshot_exit(void);
224 int dm_transient_snapshot_init(void);
225 void dm_transient_snapshot_exit(void);
227 #endif /* _LINUX_DM_EXCEPTION_STORE */
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