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205 lines
5.3 KiB
205 lines
5.3 KiB
/* |
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* Copyright (C) 2001-2002 Sistina Software (UK) Limited. |
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* Copyright (C) 2008 Red Hat, Inc. All rights reserved. |
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* |
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* Device-mapper snapshot exception store. |
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* |
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* This file is released under the GPL. |
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*/ |
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#ifndef _LINUX_DM_EXCEPTION_STORE |
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#define _LINUX_DM_EXCEPTION_STORE |
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#include <linux/blkdev.h> |
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#include <linux/list_bl.h> |
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#include <linux/device-mapper.h> |
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/* |
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* The snapshot code deals with largish chunks of the disk at a |
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* time. Typically 32k - 512k. |
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*/ |
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typedef sector_t chunk_t; |
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/* |
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* An exception is used where an old chunk of data has been |
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* replaced by a new one. |
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* If chunk_t is 64 bits in size, the top 8 bits of new_chunk hold the number |
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* of chunks that follow contiguously. Remaining bits hold the number of the |
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* chunk within the device. |
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*/ |
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struct dm_exception { |
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struct hlist_bl_node hash_list; |
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chunk_t old_chunk; |
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chunk_t new_chunk; |
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}; |
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/* |
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* Abstraction to handle the meta/layout of exception stores (the |
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* COW device). |
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*/ |
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struct dm_exception_store; |
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struct dm_exception_store_type { |
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const char *name; |
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struct module *module; |
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int (*ctr) (struct dm_exception_store *store, char *options); |
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/* |
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* Destroys this object when you've finished with it. |
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*/ |
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void (*dtr) (struct dm_exception_store *store); |
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/* |
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* The target shouldn't read the COW device until this is |
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* called. As exceptions are read from the COW, they are |
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* reported back via the callback. |
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*/ |
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int (*read_metadata) (struct dm_exception_store *store, |
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int (*callback)(void *callback_context, |
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chunk_t old, chunk_t new), |
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void *callback_context); |
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/* |
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* Find somewhere to store the next exception. |
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*/ |
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int (*prepare_exception) (struct dm_exception_store *store, |
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struct dm_exception *e); |
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/* |
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* Update the metadata with this exception. |
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*/ |
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void (*commit_exception) (struct dm_exception_store *store, |
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struct dm_exception *e, int valid, |
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void (*callback) (void *, int success), |
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void *callback_context); |
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/* |
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* Returns 0 if the exception store is empty. |
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* |
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* If there are exceptions still to be merged, sets |
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* *last_old_chunk and *last_new_chunk to the most recent |
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* still-to-be-merged chunk and returns the number of |
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* consecutive previous ones. |
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*/ |
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int (*prepare_merge) (struct dm_exception_store *store, |
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chunk_t *last_old_chunk, chunk_t *last_new_chunk); |
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/* |
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* Clear the last n exceptions. |
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* nr_merged must be <= the value returned by prepare_merge. |
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*/ |
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int (*commit_merge) (struct dm_exception_store *store, int nr_merged); |
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/* |
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* The snapshot is invalid, note this in the metadata. |
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*/ |
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void (*drop_snapshot) (struct dm_exception_store *store); |
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unsigned (*status) (struct dm_exception_store *store, |
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status_type_t status, char *result, |
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unsigned maxlen); |
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/* |
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* Return how full the snapshot is. |
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*/ |
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void (*usage) (struct dm_exception_store *store, |
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sector_t *total_sectors, sector_t *sectors_allocated, |
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sector_t *metadata_sectors); |
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/* For internal device-mapper use only. */ |
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struct list_head list; |
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}; |
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struct dm_snapshot; |
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struct dm_exception_store { |
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struct dm_exception_store_type *type; |
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struct dm_snapshot *snap; |
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/* Size of data blocks saved - must be a power of 2 */ |
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unsigned chunk_size; |
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unsigned chunk_mask; |
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unsigned chunk_shift; |
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void *context; |
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bool userspace_supports_overflow; |
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}; |
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/* |
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* Obtain the origin or cow device used by a given snapshot. |
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*/ |
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struct dm_dev *dm_snap_origin(struct dm_snapshot *snap); |
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struct dm_dev *dm_snap_cow(struct dm_snapshot *snap); |
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/* |
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* Funtions to manipulate consecutive chunks |
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*/ |
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#define DM_CHUNK_CONSECUTIVE_BITS 8 |
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#define DM_CHUNK_NUMBER_BITS 56 |
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static inline chunk_t dm_chunk_number(chunk_t chunk) |
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{ |
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return chunk & (chunk_t)((1ULL << DM_CHUNK_NUMBER_BITS) - 1ULL); |
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} |
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static inline unsigned dm_consecutive_chunk_count(struct dm_exception *e) |
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{ |
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return e->new_chunk >> DM_CHUNK_NUMBER_BITS; |
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} |
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static inline void dm_consecutive_chunk_count_inc(struct dm_exception *e) |
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{ |
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e->new_chunk += (1ULL << DM_CHUNK_NUMBER_BITS); |
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BUG_ON(!dm_consecutive_chunk_count(e)); |
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} |
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static inline void dm_consecutive_chunk_count_dec(struct dm_exception *e) |
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{ |
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BUG_ON(!dm_consecutive_chunk_count(e)); |
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e->new_chunk -= (1ULL << DM_CHUNK_NUMBER_BITS); |
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} |
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/* |
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* Return the number of sectors in the device. |
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*/ |
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static inline sector_t get_dev_size(struct block_device *bdev) |
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{ |
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return i_size_read(bdev->bd_inode) >> SECTOR_SHIFT; |
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} |
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static inline chunk_t sector_to_chunk(struct dm_exception_store *store, |
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sector_t sector) |
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{ |
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return sector >> store->chunk_shift; |
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} |
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int dm_exception_store_type_register(struct dm_exception_store_type *type); |
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int dm_exception_store_type_unregister(struct dm_exception_store_type *type); |
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int dm_exception_store_set_chunk_size(struct dm_exception_store *store, |
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unsigned chunk_size, |
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char **error); |
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int dm_exception_store_create(struct dm_target *ti, int argc, char **argv, |
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struct dm_snapshot *snap, |
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unsigned *args_used, |
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struct dm_exception_store **store); |
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void dm_exception_store_destroy(struct dm_exception_store *store); |
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int dm_exception_store_init(void); |
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void dm_exception_store_exit(void); |
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/* |
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* Two exception store implementations. |
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*/ |
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int dm_persistent_snapshot_init(void); |
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void dm_persistent_snapshot_exit(void); |
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int dm_transient_snapshot_init(void); |
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void dm_transient_snapshot_exit(void); |
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#endif /* _LINUX_DM_EXCEPTION_STORE */
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