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/*
* 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 <linux/blkdev.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 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 exception *e);
/*
* Update the metadata with this exception.
*/
void (*commit_exception) (struct exception_store *store,
struct 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;
/* The on disk metadata handler */
struct exception_store store;
struct kcopyd_client *kcopyd_client;
};
/*
* 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, uint32_t chunk_size);
int dm_create_transient(struct exception_store *store,
struct dm_snapshot *s, int blocksize);
/*
* 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
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