175 lines
3.7 KiB
C
175 lines
3.7 KiB
C
/*
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* dm-snapshot.c
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*
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* Copyright (C) 2001-2002 Sistina Software (UK) Limited.
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*
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* This file is released under the GPL.
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*/
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#ifndef DM_SNAPSHOT_H
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#define DM_SNAPSHOT_H
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#include "dm.h"
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#include "dm-bio-list.h"
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#include <linux/blkdev.h>
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#include <linux/workqueue.h>
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struct exception_table {
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uint32_t hash_mask;
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struct list_head *table;
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};
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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 64k - 256k.
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*/
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/* FIXME: can we get away with limiting these to a uint32_t ? */
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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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*/
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struct 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 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 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.
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*/
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int (*read_metadata) (struct exception_store *store);
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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 exception_store *store,
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struct 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 exception_store *store,
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struct 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 exception_store *store);
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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 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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struct dm_snapshot {
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struct rw_semaphore lock;
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struct dm_table *table;
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struct dm_dev *origin;
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struct dm_dev *cow;
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/* List of snapshots per Origin */
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struct list_head list;
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/* Size of data blocks saved - must be a power of 2 */
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chunk_t chunk_size;
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chunk_t chunk_mask;
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chunk_t chunk_shift;
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/* You can't use a snapshot if this is 0 (e.g. if full) */
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int valid;
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/* Origin writes don't trigger exceptions until this is set */
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int active;
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/* Used for display of table */
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char type;
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/* The last percentage we notified */
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int last_percent;
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struct exception_table pending;
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struct exception_table complete;
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/*
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* pe_lock protects all pending_exception operations and access
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* as well as the snapshot_bios list.
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*/
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spinlock_t pe_lock;
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/* The on disk metadata handler */
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struct exception_store store;
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struct kcopyd_client *kcopyd_client;
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/* Queue of snapshot writes for ksnapd to flush */
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struct bio_list queued_bios;
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struct work_struct queued_bios_work;
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};
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/*
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* Used by the exception stores to load exceptions hen
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* initialising.
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*/
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int dm_add_exception(struct dm_snapshot *s, chunk_t old, chunk_t new);
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/*
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* Constructor and destructor for the default persistent
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* store.
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*/
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int dm_create_persistent(struct exception_store *store);
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int dm_create_transient(struct exception_store *store);
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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 bdev->bd_inode->i_size >> SECTOR_SHIFT;
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}
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static inline chunk_t sector_to_chunk(struct dm_snapshot *s, sector_t sector)
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{
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return (sector & ~s->chunk_mask) >> s->chunk_shift;
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}
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static inline sector_t chunk_to_sector(struct dm_snapshot *s, chunk_t chunk)
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{
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return chunk << s->chunk_shift;
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}
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static inline int bdev_equal(struct block_device *lhs, struct block_device *rhs)
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{
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/*
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* There is only ever one instance of a particular block
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* device so we can compare pointers safely.
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*/
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return lhs == rhs;
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}
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#endif
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