| 1 | /* |
| 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> |
| 14 | #include <linux/device-mapper.h> |
| 15 | |
| 16 | /* |
| 17 | * The snapshot code deals with largish chunks of the disk at a |
| 18 | * time. Typically 32k - 512k. |
| 19 | */ |
| 20 | typedef 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 | */ |
| 29 | struct dm_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 | */ |
| 40 | struct dm_exception_store; |
| 41 | struct dm_exception_store_type { |
| 42 | const char *name; |
| 43 | struct module *module; |
| 44 | |
| 45 | int (*ctr) (struct dm_exception_store *store, |
| 46 | unsigned argc, char **argv); |
| 47 | |
| 48 | /* |
| 49 | * Destroys this object when you've finished with it. |
| 50 | */ |
| 51 | void (*dtr) (struct dm_exception_store *store); |
| 52 | |
| 53 | /* |
| 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. |
| 57 | */ |
| 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); |
| 62 | |
| 63 | /* |
| 64 | * Find somewhere to store the next exception. |
| 65 | */ |
| 66 | int (*prepare_exception) (struct dm_exception_store *store, |
| 67 | struct dm_exception *e); |
| 68 | |
| 69 | /* |
| 70 | * Update the metadata with this exception. |
| 71 | */ |
| 72 | void (*commit_exception) (struct dm_exception_store *store, |
| 73 | struct dm_exception *e, |
| 74 | void (*callback) (void *, int success), |
| 75 | void *callback_context); |
| 76 | |
| 77 | /* |
| 78 | * Returns 0 if the exception store is empty. |
| 79 | * |
| 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. |
| 84 | */ |
| 85 | int (*prepare_merge) (struct dm_exception_store *store, |
| 86 | chunk_t *last_old_chunk, chunk_t *last_new_chunk); |
| 87 | |
| 88 | /* |
| 89 | * Clear the last n exceptions. |
| 90 | * nr_merged must be <= the value returned by prepare_merge. |
| 91 | */ |
| 92 | int (*commit_merge) (struct dm_exception_store *store, int nr_merged); |
| 93 | |
| 94 | /* |
| 95 | * The snapshot is invalid, note this in the metadata. |
| 96 | */ |
| 97 | void (*drop_snapshot) (struct dm_exception_store *store); |
| 98 | |
| 99 | unsigned (*status) (struct dm_exception_store *store, |
| 100 | status_type_t status, char *result, |
| 101 | unsigned maxlen); |
| 102 | |
| 103 | /* |
| 104 | * Return how full the snapshot is. |
| 105 | */ |
| 106 | void (*usage) (struct dm_exception_store *store, |
| 107 | sector_t *total_sectors, sector_t *sectors_allocated, |
| 108 | sector_t *metadata_sectors); |
| 109 | |
| 110 | /* For internal device-mapper use only. */ |
| 111 | struct list_head list; |
| 112 | }; |
| 113 | |
| 114 | struct dm_snapshot; |
| 115 | |
| 116 | struct dm_exception_store { |
| 117 | struct dm_exception_store_type *type; |
| 118 | struct dm_snapshot *snap; |
| 119 | |
| 120 | /* Size of data blocks saved - must be a power of 2 */ |
| 121 | unsigned chunk_size; |
| 122 | unsigned chunk_mask; |
| 123 | unsigned chunk_shift; |
| 124 | |
| 125 | void *context; |
| 126 | }; |
| 127 | |
| 128 | /* |
| 129 | * Obtain the origin or cow device used by a given snapshot. |
| 130 | */ |
| 131 | struct dm_dev *dm_snap_origin(struct dm_snapshot *snap); |
| 132 | struct dm_dev *dm_snap_cow(struct dm_snapshot *snap); |
| 133 | |
| 134 | /* |
| 135 | * Funtions to manipulate consecutive chunks |
| 136 | */ |
| 137 | # if defined(CONFIG_LBDAF) || (BITS_PER_LONG == 64) |
| 138 | # define DM_CHUNK_CONSECUTIVE_BITS 8 |
| 139 | # define DM_CHUNK_NUMBER_BITS 56 |
| 140 | |
| 141 | static inline chunk_t dm_chunk_number(chunk_t chunk) |
| 142 | { |
| 143 | return chunk & (chunk_t)((1ULL << DM_CHUNK_NUMBER_BITS) - 1ULL); |
| 144 | } |
| 145 | |
| 146 | static inline unsigned dm_consecutive_chunk_count(struct dm_exception *e) |
| 147 | { |
| 148 | return e->new_chunk >> DM_CHUNK_NUMBER_BITS; |
| 149 | } |
| 150 | |
| 151 | static inline void dm_consecutive_chunk_count_inc(struct dm_exception *e) |
| 152 | { |
| 153 | e->new_chunk += (1ULL << DM_CHUNK_NUMBER_BITS); |
| 154 | |
| 155 | BUG_ON(!dm_consecutive_chunk_count(e)); |
| 156 | } |
| 157 | |
| 158 | static inline void dm_consecutive_chunk_count_dec(struct dm_exception *e) |
| 159 | { |
| 160 | BUG_ON(!dm_consecutive_chunk_count(e)); |
| 161 | |
| 162 | e->new_chunk -= (1ULL << DM_CHUNK_NUMBER_BITS); |
| 163 | } |
| 164 | |
| 165 | # else |
| 166 | # define DM_CHUNK_CONSECUTIVE_BITS 0 |
| 167 | |
| 168 | static inline chunk_t dm_chunk_number(chunk_t chunk) |
| 169 | { |
| 170 | return chunk; |
| 171 | } |
| 172 | |
| 173 | static inline unsigned dm_consecutive_chunk_count(struct dm_exception *e) |
| 174 | { |
| 175 | return 0; |
| 176 | } |
| 177 | |
| 178 | static inline void dm_consecutive_chunk_count_inc(struct dm_exception *e) |
| 179 | { |
| 180 | } |
| 181 | |
| 182 | static inline void dm_consecutive_chunk_count_dec(struct dm_exception *e) |
| 183 | { |
| 184 | } |
| 185 | |
| 186 | # endif |
| 187 | |
| 188 | /* |
| 189 | * Return the number of sectors in the device. |
| 190 | */ |
| 191 | static inline sector_t get_dev_size(struct block_device *bdev) |
| 192 | { |
| 193 | return i_size_read(bdev->bd_inode) >> SECTOR_SHIFT; |
| 194 | } |
| 195 | |
| 196 | static inline chunk_t sector_to_chunk(struct dm_exception_store *store, |
| 197 | sector_t sector) |
| 198 | { |
| 199 | return sector >> store->chunk_shift; |
| 200 | } |
| 201 | |
| 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); |
| 204 | |
| 205 | int dm_exception_store_set_chunk_size(struct dm_exception_store *store, |
| 206 | unsigned chunk_size, |
| 207 | char **error); |
| 208 | |
| 209 | int dm_exception_store_create(struct dm_target *ti, int argc, char **argv, |
| 210 | struct dm_snapshot *snap, |
| 211 | unsigned *args_used, |
| 212 | struct dm_exception_store **store); |
| 213 | void dm_exception_store_destroy(struct dm_exception_store *store); |
| 214 | |
| 215 | int dm_exception_store_init(void); |
| 216 | void dm_exception_store_exit(void); |
| 217 | |
| 218 | /* |
| 219 | * Two exception store implementations. |
| 220 | */ |
| 221 | int dm_persistent_snapshot_init(void); |
| 222 | void dm_persistent_snapshot_exit(void); |
| 223 | |
| 224 | int dm_transient_snapshot_init(void); |
| 225 | void dm_transient_snapshot_exit(void); |
| 226 | |
| 227 | #endif /* _LINUX_DM_EXCEPTION_STORE */ |