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/*
* Copyright (C) 2001-2002 Sistina Software (UK) Limited.
* Copyright (C) 2008 Red Hat, Inc. All rights reserved.
*
* Device-mapper snapshot exception store.
*
* This file is released under the GPL.
*/
#ifndef _LINUX_DM_EXCEPTION_STORE
#define _LINUX_DM_EXCEPTION_STORE
#include <linux/blkdev.h>
/*
* The snapshot code deals with largish chunks of the disk at a
* time. Typically 32k - 512k.
*/
typedef sector_t chunk_t;
/*
* An exception is used where an old chunk of data has been
* replaced by a new one.
* If chunk_t is 64 bits in size, the top 8 bits of new_chunk hold the number
* of chunks that follow contiguously. Remaining bits hold the number of the
* chunk within the device.
*/
struct dm_snap_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 dm_snap_exception *e);
/*
* Update the metadata with this exception.
*/
void (*commit_exception) (struct exception_store *store,
struct dm_snap_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;
};
/*
* Funtions to manipulate consecutive chunks
*/
# if defined(CONFIG_LBD) || (BITS_PER_LONG == 64)
# define DM_CHUNK_CONSECUTIVE_BITS 8
# define DM_CHUNK_NUMBER_BITS 56
static inline chunk_t dm_chunk_number(chunk_t chunk)
{
return chunk & (chunk_t)((1ULL << DM_CHUNK_NUMBER_BITS) - 1ULL);
}
static inline unsigned dm_consecutive_chunk_count(struct dm_snap_exception *e)
{
return e->new_chunk >> DM_CHUNK_NUMBER_BITS;
}
static inline void dm_consecutive_chunk_count_inc(struct dm_snap_exception *e)
{
e->new_chunk += (1ULL << DM_CHUNK_NUMBER_BITS);
BUG_ON(!dm_consecutive_chunk_count(e));
}
# else
# define DM_CHUNK_CONSECUTIVE_BITS 0
static inline chunk_t dm_chunk_number(chunk_t chunk)
{
return chunk;
}
static inline unsigned dm_consecutive_chunk_count(struct dm_snap_exception *e)
{
return 0;
}
static inline void dm_consecutive_chunk_count_inc(struct dm_snap_exception *e)
{
}
# endif
/*
* Two exception store implementations.
*/
int dm_create_persistent(struct exception_store *store);
int dm_create_transient(struct exception_store *store);
#endif /* _LINUX_DM_EXCEPTION_STORE */
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