dm-exception-store.h | Explore in Territory

/* SPDX-License-Identifier: GPL-2.0-only */
/*
 * 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.
 */
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 { … };

/*
 * Abstraction to handle the meta/layout of exception stores (the
 * COW device).
 */
struct dm_exception_store;
struct dm_exception_store_type { … };

struct dm_snapshot;

struct dm_exception_store { … };

/*
 * 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 …
#define DM_CHUNK_NUMBER_BITS …

static inline chunk_t dm_chunk_number(chunk_t chunk)
{ … }

static inline unsigned int dm_consecutive_chunk_count(struct dm_exception *e)
{ … }

static inline void dm_consecutive_chunk_count_inc(struct dm_exception *e)
{ … }

static inline void dm_consecutive_chunk_count_dec(struct dm_exception *e)
{ … }

/*
 * Return the number of sectors in the device.
 */
static inline sector_t get_dev_size(struct block_device *bdev)
{ … }

static inline chunk_t sector_to_chunk(struct dm_exception_store *store,
				      sector_t sector)
{ … }

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 int chunk_size,
				      char **error);

int dm_exception_store_create(struct dm_target *ti, int argc, char **argv,
			      struct dm_snapshot *snap,
			      unsigned int *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 */
linux/drivers/md/dm-exception-store.h
