Commit aea53d92 authored by Jonathan Brassow's avatar Jonathan Brassow Committed by Alasdair G Kergon
Browse files

dm snapshot: separate out exception store interface 



Pull structures that bridge the gap between snapshot and
exception store out of dm-snap.h and put them in a new
.h file - dm-exception-store.h.  This file will define the
API for new exception stores.

Ultimately, dm-snap.h is unnecessary, since only dm-snap.c
should be using it.

Signed-off-by: default avatarJonathan Brassow <jbrassow@redhat.com>
Signed-off-by: default avatarAlasdair G Kergon <agk@redhat.com>
parent fe9cf30e

drivers/md/dm-exception-store.c

+1 −0
Original line number Diff line number Diff line
@@ -7,6 +7,7 @@ 
 * This file is released under the GPL.

 */



#include "dm-exception-store.h"

#include "dm-snap.h"



#include <linux/mm.h>

drivers/md/dm-exception-store.h

0 → 100644
+131 −0
Original line number Diff line number Diff line 
/*

 * 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 */

drivers/md/dm-snap.c

+1 −0
Original line number Diff line number Diff line
@@ -21,6 +21,7 @@ 
#include <linux/log2.h>

#include <linux/dm-kcopyd.h>



#include "dm-exception-store.h"

#include "dm-snap.h"

#include "dm-bio-list.h"

drivers/md/dm-snap.h

+1 −120
Original line number Diff line number Diff line 
/*

 * dm-snapshot.c

 *

 * Copyright (C) 2001-2002 Sistina Software (UK) Limited.

 *

 * This file is released under the GPL.
@@ -10,6 +8,7 @@ 
#define DM_SNAPSHOT_H



#include <linux/device-mapper.h>

#include "dm-exception-store.h"

#include "dm-bio-list.h"

#include <linux/blkdev.h>

#include <linux/workqueue.h>
@@ -20,116 +19,6 @@ struct exception_table { 
	struct list_head *table;

};



/*

 * 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;

};



/*

 * 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



/*

 * 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;

};



#define DM_TRACKED_CHUNK_HASH_SIZE	16

#define DM_TRACKED_CHUNK_HASH(x)	((unsigned long)(x) & \

					 (DM_TRACKED_CHUNK_HASH_SIZE - 1))
@@ -192,14 +81,6 @@ struct dm_snapshot { 
 */

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);



int dm_create_transient(struct exception_store *store);



/*

 * Return the number of sectors in the device.

 */

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