1 /* SPDX-License-Identifier: GPL-2.0-only */
3 * Copyright (C) 2001-2002 Sistina Software (UK) Limited.
4 * Copyright (C) 2008 Red Hat, Inc. All rights reserved.
6 * Device-mapper snapshot exception store.
8 * This file is released under the GPL.
11 #ifndef _LINUX_DM_EXCEPTION_STORE
12 #define _LINUX_DM_EXCEPTION_STORE
14 #include <linux/blkdev.h>
15 #include <linux/list_bl.h>
16 #include <linux/device-mapper.h>
19 * The snapshot code deals with largish chunks of the disk at a
20 * time. Typically 32k - 512k.
22 typedef sector_t chunk_t
;
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.
32 struct hlist_bl_node hash_list
;
39 * Abstraction to handle the meta/layout of exception stores (the
42 struct dm_exception_store
;
43 struct dm_exception_store_type
{
45 struct module
*module
;
47 int (*ctr
)(struct dm_exception_store
*store
, char *options
);
50 * Destroys this object when you've finished with it.
52 void (*dtr
)(struct dm_exception_store
*store
);
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.
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
);
65 * Find somewhere to store the next exception.
67 int (*prepare_exception
)(struct dm_exception_store
*store
,
68 struct dm_exception
*e
);
71 * Update the metadata with this exception.
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
);
79 * Returns 0 if the exception store is empty.
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.
86 int (*prepare_merge
)(struct dm_exception_store
*store
,
87 chunk_t
*last_old_chunk
, chunk_t
*last_new_chunk
);
90 * Clear the last n exceptions.
91 * nr_merged must be <= the value returned by prepare_merge.
93 int (*commit_merge
)(struct dm_exception_store
*store
, int nr_merged
);
96 * The snapshot is invalid, note this in the metadata.
98 void (*drop_snapshot
)(struct dm_exception_store
*store
);
100 unsigned int (*status
)(struct dm_exception_store
*store
,
101 status_type_t status
, char *result
,
102 unsigned int maxlen
);
105 * Return how full the snapshot is.
107 void (*usage
)(struct dm_exception_store
*store
,
108 sector_t
*total_sectors
, sector_t
*sectors_allocated
,
109 sector_t
*metadata_sectors
);
111 /* For internal device-mapper use only. */
112 struct list_head list
;
117 struct dm_exception_store
{
118 struct dm_exception_store_type
*type
;
119 struct dm_snapshot
*snap
;
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
;
128 bool userspace_supports_overflow
;
132 * Obtain the origin or cow device used by a given snapshot.
134 struct dm_dev
*dm_snap_origin(struct dm_snapshot
*snap
);
135 struct dm_dev
*dm_snap_cow(struct dm_snapshot
*snap
);
138 * Funtions to manipulate consecutive chunks
140 #define DM_CHUNK_CONSECUTIVE_BITS 8
141 #define DM_CHUNK_NUMBER_BITS 56
143 static inline chunk_t
dm_chunk_number(chunk_t chunk
)
145 return chunk
& (chunk_t
)((1ULL << DM_CHUNK_NUMBER_BITS
) - 1ULL);
148 static inline unsigned int dm_consecutive_chunk_count(struct dm_exception
*e
)
150 return e
->new_chunk
>> DM_CHUNK_NUMBER_BITS
;
153 static inline void dm_consecutive_chunk_count_inc(struct dm_exception
*e
)
155 e
->new_chunk
+= (1ULL << DM_CHUNK_NUMBER_BITS
);
157 BUG_ON(!dm_consecutive_chunk_count(e
));
160 static inline void dm_consecutive_chunk_count_dec(struct dm_exception
*e
)
162 BUG_ON(!dm_consecutive_chunk_count(e
));
164 e
->new_chunk
-= (1ULL << DM_CHUNK_NUMBER_BITS
);
168 * Return the number of sectors in the device.
170 static inline sector_t
get_dev_size(struct block_device
*bdev
)
172 return bdev_nr_sectors(bdev
);
175 static inline chunk_t
sector_to_chunk(struct dm_exception_store
*store
,
178 return sector
>> store
->chunk_shift
;
181 int dm_exception_store_type_register(struct dm_exception_store_type
*type
);
182 int dm_exception_store_type_unregister(struct dm_exception_store_type
*type
);
184 int dm_exception_store_set_chunk_size(struct dm_exception_store
*store
,
185 unsigned int chunk_size
,
188 int 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
);
192 void dm_exception_store_destroy(struct dm_exception_store
*store
);
194 int dm_exception_store_init(void);
195 void dm_exception_store_exit(void);
198 * Two exception store implementations.
200 int dm_persistent_snapshot_init(void);
201 void dm_persistent_snapshot_exit(void);
203 int dm_transient_snapshot_init(void);
204 void dm_transient_snapshot_exit(void);
206 #endif /* _LINUX_DM_EXCEPTION_STORE */