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 {
42 int (*ctr) (struct dm_exception_store *store,
43 unsigned argc, char **argv);
46 * Destroys this object when you've finished with it.
48 void (*dtr) (struct dm_exception_store *store);
51 * The target shouldn't read the COW device until this is
52 * called. As exceptions are read from the COW, they are
53 * reported back via the callback.
55 int (*read_metadata) (struct dm_exception_store *store,
56 int (*callback)(void *callback_context,
57 chunk_t old, chunk_t new),
58 void *callback_context);
61 * Find somewhere to store the next exception.
63 int (*prepare_exception) (struct dm_exception_store *store,
64 struct dm_snap_exception *e);
67 * Update the metadata with this exception.
69 void (*commit_exception) (struct dm_exception_store *store,
70 struct dm_snap_exception *e,
71 void (*callback) (void *, int success),
72 void *callback_context);
75 * The snapshot is invalid, note this in the metadata.
77 void (*drop_snapshot) (struct dm_exception_store *store);
79 int (*status) (struct dm_exception_store *store, status_type_t status,
80 char *result, unsigned int maxlen);
83 * Return how full the snapshot is.
85 void (*fraction_full) (struct dm_exception_store *store,
87 sector_t *denominator);
90 struct dm_exception_store {
91 struct dm_exception_store_type type;
93 struct dm_snapshot *snap;
99 * Funtions to manipulate consecutive chunks
101 # if defined(CONFIG_LBD) || (BITS_PER_LONG == 64)
102 # define DM_CHUNK_CONSECUTIVE_BITS 8
103 # define DM_CHUNK_NUMBER_BITS 56
105 static inline chunk_t dm_chunk_number(chunk_t chunk)
107 return chunk & (chunk_t)((1ULL << DM_CHUNK_NUMBER_BITS) - 1ULL);
110 static inline unsigned dm_consecutive_chunk_count(struct dm_snap_exception *e)
112 return e->new_chunk >> DM_CHUNK_NUMBER_BITS;
115 static inline void dm_consecutive_chunk_count_inc(struct dm_snap_exception *e)
117 e->new_chunk += (1ULL << DM_CHUNK_NUMBER_BITS);
119 BUG_ON(!dm_consecutive_chunk_count(e));
123 # define DM_CHUNK_CONSECUTIVE_BITS 0
125 static inline chunk_t dm_chunk_number(chunk_t chunk)
130 static inline unsigned dm_consecutive_chunk_count(struct dm_snap_exception *e)
135 static inline void dm_consecutive_chunk_count_inc(struct dm_snap_exception *e)
141 int dm_exception_store_init(void);
142 void dm_exception_store_exit(void);
145 * Two exception store implementations.
147 int dm_persistent_snapshot_init(void);
148 void dm_persistent_snapshot_exit(void);
150 int dm_transient_snapshot_init(void);
151 void dm_transient_snapshot_exit(void);
153 int dm_create_persistent(struct dm_exception_store *store);
155 int dm_create_transient(struct dm_exception_store *store);
157 #endif /* _LINUX_DM_EXCEPTION_STORE */