[linux.git] / drivers / md / dm-snap.h

/*
 * 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
Commit	Line	Data
1da177e4 LT	1	/*
	2	* dm-snapshot.c
	3	*
	4	* Copyright (C) 2001-2002 Sistina Software (UK) Limited.
	5	*
	6	* This file is released under the GPL.
	7	*/
	8
	9	#ifndef DM_SNAPSHOT_H
	10	#define DM_SNAPSHOT_H
	11
	12	#include "dm.h"
	13	#include <linux/blkdev.h>
	14
	15	struct exception_table {
	16	uint32_t hash_mask;
	17	struct list_head *table;
	18	};
	19
	20	/*
	21	* The snapshot code deals with largish chunks of the disk at a
	22	* time. Typically 64k - 256k.
	23	*/
	24	/* FIXME: can we get away with limiting these to a uint32_t ? */
	25	typedef sector_t chunk_t;
	26
	27	/*
	28	* An exception is used where an old chunk of data has been
	29	* replaced by a new one.
	30	*/
	31	struct exception {
	32	struct list_head hash_list;
	33
	34	chunk_t old_chunk;
	35	chunk_t new_chunk;
	36	};
	37
	38	/*
	39	* Abstraction to handle the meta/layout of exception stores (the
	40	* COW device).
	41	*/
	42	struct exception_store {
	43
	44	/*
	45	* Destroys this object when you've finished with it.
	46	*/
	47	void (destroy) (struct exception_store store);
	48
	49	/*
	50	* The target shouldn't read the COW device until this is
	51	* called.
	52	*/
	53	int (read_metadata) (struct exception_store store);
	54
	55	/*
	56	* Find somewhere to store the next exception.
	57	*/
	58	int (prepare_exception) (struct exception_store store,
	59	struct exception *e);
	60
	61	/*
	62	* Update the metadata with this exception.
	63	*/
	64	void (commit_exception) (struct exception_store store,
65	struct exception *e,
66	void (callback) (void , int success),
67	void *callback_context);
68
69	/*
70	* The snapshot is invalid, note this in the metadata.
71	*/
72	void (drop_snapshot) (struct exception_store store);
73
74	/*
75	* Return how full the snapshot is.
76	*/
77	void (fraction_full) (struct exception_store store,
78	sector_t *numerator,
79	sector_t *denominator);
80
81	struct dm_snapshot *snap;
82	void *context;
83	};
84
85	struct dm_snapshot {
86	struct rw_semaphore lock;
87	struct dm_table *table;
88
89	struct dm_dev *origin;
90	struct dm_dev *cow;
91
92	/* List of snapshots per Origin */
93	struct list_head list;
94
95	/* Size of data blocks saved - must be a power of 2 */
96	chunk_t chunk_size;
97	chunk_t chunk_mask;
98	chunk_t chunk_shift;
99
100	/* You can't use a snapshot if this is 0 (e.g. if full) */
101	int valid;
aa14edeb AK	102
	103	/* Origin writes don't trigger exceptions until this is set */
	104	int active;
1da177e4 LT	105
	106	/* Used for display of table */
	107	char type;
	108
	109	/* The last percentage we notified */
	110	int last_percent;
	111
	112	struct exception_table pending;
	113	struct exception_table complete;
	114
	115	/* The on disk metadata handler */
	116	struct exception_store store;
	117
	118	struct kcopyd_client *kcopyd_client;
	119	};
	120
	121	/*
	122	* Used by the exception stores to load exceptions hen
	123	* initialising.
	124	*/
	125	int dm_add_exception(struct dm_snapshot *s, chunk_t old, chunk_t new);
	126
	127	/*
	128	* Constructor and destructor for the default persistent
	129	* store.
	130	*/
	131	int dm_create_persistent(struct exception_store *store, uint32_t chunk_size);
	132
	133	int dm_create_transient(struct exception_store *store,
	134	struct dm_snapshot *s, int blocksize);
	135
	136	/*
	137	* Return the number of sectors in the device.
	138	*/
	139	static inline sector_t get_dev_size(struct block_device *bdev)
	140	{
	141	return bdev->bd_inode->i_size >> SECTOR_SHIFT;
	142	}
	143
	144	static inline chunk_t sector_to_chunk(struct dm_snapshot *s, sector_t sector)
	145	{
	146	return (sector & ~s->chunk_mask) >> s->chunk_shift;
	147	}
	148
	149	static inline sector_t chunk_to_sector(struct dm_snapshot *s, chunk_t chunk)
	150	{
	151	return chunk << s->chunk_shift;
	152	}
	153
	154	static inline int bdev_equal(struct block_device lhs, struct block_device rhs)
	155	{
	156	/*
	157	* There is only ever one instance of a particular block
	158	* device so we can compare pointers safely.
	159	*/
	160	return lhs == rhs;
	161	}
	162
	163	#endif