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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>
#include <linux/list_bl.h>
#include <linux/device-mapper.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_exception {
struct hlist_bl_node hash_list;
chunk_t old_chunk;
chunk_t new_chunk;
};
/*
* Abstraction to handle the meta/layout of exception stores (the
* COW device).
*/
struct dm_exception_store;
struct dm_exception_store_type {
const char *name;
struct module *module;
int (*ctr) (struct dm_exception_store *store, char *options);
/*
* Destroys this object when you've finished with it.
*/
void (*dtr) (struct dm_exception_store *store);
/*
* The target shouldn't read the COW device until this is
* called. As exceptions are read from the COW, they are
* reported back via the callback.
*/
int (*read_metadata) (struct dm_exception_store *store,
int (*callback)(void *callback_context,
chunk_t old, chunk_t new),
void *callback_context);
/*
* Find somewhere to store the next exception.
*/
int (*prepare_exception) (struct dm_exception_store *store,
struct dm_exception *e);
/*
* Update the metadata with this exception.
*/
void (*commit_exception) (struct dm_exception_store *store,
struct dm_exception *e, int valid,
void (*callback) (void *, int success),
void *callback_context);
/*
* Returns 0 if the exception store is empty.
*
* If there are exceptions still to be merged, sets
* *last_old_chunk and *last_new_chunk to the most recent
* still-to-be-merged chunk and returns the number of
* consecutive previous ones.
*/
int (*prepare_merge) (struct dm_exception_store *store,
chunk_t *last_old_chunk, chunk_t *last_new_chunk);
/*
* Clear the last n exceptions.
* nr_merged must be <= the value returned by prepare_merge.
*/
int (*commit_merge) (struct dm_exception_store *store, int nr_merged);
/*
* The snapshot is invalid, note this in the metadata.
*/
void (*drop_snapshot) (struct dm_exception_store *store);
unsigned (*status) (struct dm_exception_store *store,
status_type_t status, char *result,
unsigned maxlen);
/*
* Return how full the snapshot is.
*/
void (*usage) (struct dm_exception_store *store,
sector_t *total_sectors, sector_t *sectors_allocated,
sector_t *metadata_sectors);
/* For internal device-mapper use only. */
struct list_head list;
};
struct dm_snapshot;
struct dm_exception_store {
struct dm_exception_store_type *type;
struct dm_snapshot *snap;
/* Size of data blocks saved - must be a power of 2 */
unsigned chunk_size;
unsigned chunk_mask;
unsigned chunk_shift;
void *context;
bool userspace_supports_overflow;
};
/*
* Obtain the origin or cow device used by a given snapshot.
*/
struct dm_dev *dm_snap_origin(struct dm_snapshot *snap);
struct dm_dev *dm_snap_cow(struct dm_snapshot *snap);
/*
* Funtions to manipulate consecutive chunks
*/
#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_exception *e)
{
return e->new_chunk >> DM_CHUNK_NUMBER_BITS;
}
static inline void dm_consecutive_chunk_count_inc(struct dm_exception *e)
{
e->new_chunk += (1ULL << DM_CHUNK_NUMBER_BITS);
BUG_ON(!dm_consecutive_chunk_count(e));
}
static inline void dm_consecutive_chunk_count_dec(struct dm_exception *e)
{
BUG_ON(!dm_consecutive_chunk_count(e));
e->new_chunk -= (1ULL << DM_CHUNK_NUMBER_BITS);
}
/*
* Return the number of sectors in the device.
*/
static inline sector_t get_dev_size(struct block_device *bdev)
{
return i_size_read(bdev->bd_inode) >> SECTOR_SHIFT;
}
static inline chunk_t sector_to_chunk(struct dm_exception_store *store,
sector_t sector)
{
return sector >> store->chunk_shift;
}
int dm_exception_store_type_register(struct dm_exception_store_type *type);
int dm_exception_store_type_unregister(struct dm_exception_store_type *type);
int dm_exception_store_set_chunk_size(struct dm_exception_store *store,
unsigned chunk_size,
char **error);
int dm_exception_store_create(struct dm_target *ti, int argc, char **argv,
struct dm_snapshot *snap,
unsigned *args_used,
struct dm_exception_store **store);
void dm_exception_store_destroy(struct dm_exception_store *store);
int dm_exception_store_init(void);
void dm_exception_store_exit(void);
/*
* Two exception store implementations.
*/
int dm_persistent_snapshot_init(void);
void dm_persistent_snapshot_exit(void);
int dm_transient_snapshot_init(void);
void dm_transient_snapshot_exit(void);
#endif /* _LINUX_DM_EXCEPTION_STORE */
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