149 lines
3.5 KiB
C
149 lines
3.5 KiB
C
/*
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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/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_snap_exception {
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struct list_head 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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/*
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* Destroys this object when you've finished with it.
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*/
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void (*destroy) (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_snap_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_snap_exception *e,
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void (*callback) (void *, int success),
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void *callback_context);
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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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int (*status) (struct dm_exception_store *store, status_type_t status,
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char *result, unsigned int maxlen);
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/*
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* Return how full the snapshot is.
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*/
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void (*fraction_full) (struct dm_exception_store *store,
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sector_t *numerator,
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sector_t *denominator);
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struct dm_snapshot *snap;
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void *context;
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};
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/*
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* Funtions to manipulate consecutive chunks
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*/
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# if defined(CONFIG_LBD) || (BITS_PER_LONG == 64)
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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_snap_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_snap_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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# else
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# define DM_CHUNK_CONSECUTIVE_BITS 0
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static inline chunk_t dm_chunk_number(chunk_t chunk)
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{
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return chunk;
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}
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static inline unsigned dm_consecutive_chunk_count(struct dm_snap_exception *e)
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{
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return 0;
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}
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static inline void dm_consecutive_chunk_count_inc(struct dm_snap_exception *e)
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{
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}
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# endif
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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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int dm_create_persistent(struct dm_exception_store *store);
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int dm_create_transient(struct dm_exception_store *store);
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#endif /* _LINUX_DM_EXCEPTION_STORE */
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