aa14edeb99
Move snapshot metadata loading to happen when the table is created instead of when the device is resumed. Writes to the origin device don't trigger exceptions until each snapshot table becomes active when resume() is called on each snapshot. If you're using lvm2, for this patch to work properly you should update to lvm2 version 2.02.01 or later and device-mapper version 1.02.02 or later. Signed-off-by: Alasdair G Kergon <agk@redhat.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
164 lines
3.4 KiB
C
164 lines
3.4 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 <linux/blkdev.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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/* 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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};
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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, uint32_t chunk_size);
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int dm_create_transient(struct exception_store *store,
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struct dm_snapshot *s, int blocksize);
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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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