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dm snapshot: separate out exception store interface

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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: Jonathan Brassow <jbrassow@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
This commit is contained in:
Jonathan Brassow 2009-01-06 03:05:15 +00:00 • committed by Alasdair G Kergon
parent fe9cf30eb8
commit aea53d92f7
4 changed files with 134 additions and 120 deletions
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1
drivers/md/dm-exception-store.c
View file

@ -7,6 +7,7 @@
* This file is released under the GPL. * This file is released under the GPL.
*/ */
#include "dm-exception-store.h"
#include "dm-snap.h" #include "dm-snap.h"
#include <linux/mm.h> #include <linux/mm.h>

131
drivers/md/dm-exception-store.h Normal file
View file

@ -0,0 +1,131 @@
/*
* 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 */

1
drivers/md/dm-snap.c
View file

@ -21,6 +21,7 @@
#include <linux/log2.h> #include <linux/log2.h>
#include <linux/dm-kcopyd.h> #include <linux/dm-kcopyd.h>
#include "dm-exception-store.h"
#include "dm-snap.h" #include "dm-snap.h"
#include "dm-bio-list.h" #include "dm-bio-list.h"

121
drivers/md/dm-snap.h
View file

@ -1,6 +1,4 @@
/* /*
* dm-snapshot.c
*
* Copyright (C) 2001-2002 Sistina Software (UK) Limited. * Copyright (C) 2001-2002 Sistina Software (UK) Limited.
* *
* This file is released under the GPL. * This file is released under the GPL.
@ -10,6 +8,7 @@
#define DM_SNAPSHOT_H #define DM_SNAPSHOT_H
#include <linux/device-mapper.h> #include <linux/device-mapper.h>
#include "dm-exception-store.h"
#include "dm-bio-list.h" #include "dm-bio-list.h"
#include <linux/blkdev.h> #include <linux/blkdev.h>
#include <linux/workqueue.h> #include <linux/workqueue.h>
@ -20,116 +19,6 @@ struct exception_table {
struct list_head *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_SIZE 16
#define DM_TRACKED_CHUNK_HASH(x) ((unsigned long)(x) & \ #define DM_TRACKED_CHUNK_HASH(x) ((unsigned long)(x) & \
(DM_TRACKED_CHUNK_HASH_SIZE - 1)) (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); 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. * Return the number of sectors in the device.
*/ */