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.
29 struct dm_snap_exception {
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_snap_exception *e);
70 * Update the metadata with this exception.
72 void (*commit_exception) (struct dm_exception_store *store,
73 struct dm_snap_exception *e,
74 void (*callback) (void *, int success),
75 void *callback_context);
78 * The snapshot is invalid, note this in the metadata.
80 void (*drop_snapshot) (struct dm_exception_store *store);
82 int (*status) (struct dm_exception_store *store, status_type_t status,
83 char *result, unsigned int maxlen);
86 * Return how full the snapshot is.
88 void (*fraction_full) (struct dm_exception_store *store,
90 sector_t *denominator);
92 /* For internal device-mapper use only. */
93 struct list_head list;
96 struct dm_exception_store {
97 struct dm_exception_store_type *type;
99 struct dm_snapshot *snap;
105 * Funtions to manipulate consecutive chunks
107 # if defined(CONFIG_LBD) || (BITS_PER_LONG == 64)
108 # define DM_CHUNK_CONSECUTIVE_BITS 8
109 # define DM_CHUNK_NUMBER_BITS 56
111 static inline chunk_t dm_chunk_number(chunk_t chunk)
113 return chunk & (chunk_t)((1ULL << DM_CHUNK_NUMBER_BITS) - 1ULL);
116 static inline unsigned dm_consecutive_chunk_count(struct dm_snap_exception *e)
118 return e->new_chunk >> DM_CHUNK_NUMBER_BITS;
121 static inline void dm_consecutive_chunk_count_inc(struct dm_snap_exception *e)
123 e->new_chunk += (1ULL << DM_CHUNK_NUMBER_BITS);
125 BUG_ON(!dm_consecutive_chunk_count(e));
129 # define DM_CHUNK_CONSECUTIVE_BITS 0
131 static inline chunk_t dm_chunk_number(chunk_t chunk)
136 static inline unsigned dm_consecutive_chunk_count(struct dm_snap_exception *e)
141 static inline void dm_consecutive_chunk_count_inc(struct dm_snap_exception *e)
147 int dm_exception_store_type_register(struct dm_exception_store_type *type);
148 int dm_exception_store_type_unregister(struct dm_exception_store_type *type);
150 int dm_exception_store_create(const char *type_name,
151 struct dm_exception_store **store);
152 void dm_exception_store_destroy(struct dm_exception_store *store);
154 int dm_exception_store_init(void);
155 void dm_exception_store_exit(void);
158 * Two exception store implementations.
160 int dm_persistent_snapshot_init(void);
161 void dm_persistent_snapshot_exit(void);
163 int dm_transient_snapshot_init(void);
164 void dm_transient_snapshot_exit(void);
166 #endif /* _LINUX_DM_EXCEPTION_STORE */