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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 | /* * dm-snapshot.c * * Copyright (C) 2001-2002 Sistina Software (UK) Limited. * * This file is released under the GPL. */ #ifndef DM_SNAPSHOT_H #define DM_SNAPSHOT_H #include "dm.h" #include "dm-bio-list.h" #include <linux/blkdev.h> #include <linux/workqueue.h> struct exception_table { uint32_t hash_mask; struct list_head *table; }; /* * The snapshot code deals with largish chunks of the disk at a * time. Typically 64k - 256k. */ /* FIXME: can we get away with limiting these to a uint32_t ? */ typedef sector_t chunk_t; /* * An exception is used where an old chunk of data has been * replaced by a new one. */ struct dm_snap_exception { struct list_head hash_list; chunk_t old_chunk; chunk_t new_chunk; }; /* * Abstraction to handle the meta/layout of exception stores (the * COW device). */ struct exception_store { /* * Destroys this object when you've finished with it. */ void (*destroy) (struct exception_store *store); /* * The target shouldn't read the COW device until this is * called. */ int (*read_metadata) (struct exception_store *store); /* * Find somewhere to store the next exception. */ int (*prepare_exception) (struct exception_store *store, struct dm_snap_exception *e); /* * Update the metadata with this exception. */ void (*commit_exception) (struct exception_store *store, struct dm_snap_exception *e, void (*callback) (void *, int success), void *callback_context); /* * The snapshot is invalid, note this in the metadata. */ void (*drop_snapshot) (struct exception_store *store); /* * Return how full the snapshot is. */ void (*fraction_full) (struct exception_store *store, sector_t *numerator, sector_t *denominator); struct dm_snapshot *snap; void *context; }; struct dm_snapshot { struct rw_semaphore lock; struct dm_table *table; struct dm_dev *origin; struct dm_dev *cow; /* List of snapshots per Origin */ struct list_head list; /* Size of data blocks saved - must be a power of 2 */ chunk_t chunk_size; chunk_t chunk_mask; chunk_t chunk_shift; /* You can't use a snapshot if this is 0 (e.g. if full) */ int valid; /* Origin writes don't trigger exceptions until this is set */ int active; /* Used for display of table */ char type; /* The last percentage we notified */ int last_percent; struct exception_table pending; struct exception_table complete; /* * pe_lock protects all pending_exception operations and access * as well as the snapshot_bios list. */ spinlock_t pe_lock; /* The on disk metadata handler */ struct exception_store store; struct kcopyd_client *kcopyd_client; /* Queue of snapshot writes for ksnapd to flush */ struct bio_list queued_bios; struct work_struct queued_bios_work; }; /* * Used by the exception stores to load exceptions hen * initialising. */ int dm_add_exception(struct dm_snapshot *s, chunk_t old, chunk_t new); /* * Constructor and destructor for the default persistent * store. */ int dm_create_persistent(struct exception_store *store); int dm_create_transient(struct exception_store *store); /* * Return the number of sectors in the device. */ static inline sector_t get_dev_size(struct block_device *bdev) { return bdev->bd_inode->i_size >> SECTOR_SHIFT; } static inline chunk_t sector_to_chunk(struct dm_snapshot *s, sector_t sector) { return (sector & ~s->chunk_mask) >> s->chunk_shift; } static inline sector_t chunk_to_sector(struct dm_snapshot *s, chunk_t chunk) { return chunk << s->chunk_shift; } static inline int bdev_equal(struct block_device *lhs, struct block_device *rhs) { /* * There is only ever one instance of a particular block * device so we can compare pointers safely. */ return lhs == rhs; } #endif |