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[PATCH] device-mapper snapshot: load metadata on creation 

Move snapshot metadata loading to happen when the table is created instead of
when the device is resumed.  Writes to the origin device don't trigger
exceptions until each snapshot table becomes active when resume() is called on
each snapshot.

If you're using lvm2, for this patch to work properly you should update to
lvm2 version 2.02.01 or later and device-mapper version 1.02.02 or later.

Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Alasdair G Kergon 2006-02-01 03:04:50 -08:00 committed by Linus Torvalds
parent cb82a6cdf9
commit aa14edeb99
2 changed files with 15 additions and 12 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

23
drivers/md/dm-snap.c
View File

@ -373,16 +373,11 @@ static inline ulong round_up(ulong n, ulong size)
static void read_snapshot_metadata(struct dm_snapshot *s)
{
if (s->have_metadata)
return;
if (s->store.read_metadata(&s->store)) {
down_write(&s->lock);
s->valid = 0;
up_write(&s->lock);
}
s->have_metadata = 1;
}
/*
@ -471,7 +466,7 @@ static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv)
s->chunk_shift = ffs(chunk_size) - 1;
s->valid = 1;
s->have_metadata = 0;
s->active = 0;
s->last_percent = 0;
init_rwsem(&s->lock);
s->table = ti->table;
@ -506,7 +501,11 @@ static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv)
goto bad5;
}
/* Metadata must only be loaded into one table at once */
read_snapshot_metadata(s);
/* Add snapshot to the list of snapshots for this origin */
/* Exceptions aren't triggered till snapshot_resume() is called */
if (register_snapshot(s)) {
r = -EINVAL;
ti->error = "Cannot register snapshot origin";
@ -862,7 +861,9 @@ static void snapshot_resume(struct dm_target *ti)
{
struct dm_snapshot *s = (struct dm_snapshot *) ti->private;
read_snapshot_metadata(s);
down_write(&s->lock);
s->active = 1;
up_write(&s->lock);
}
static int snapshot_status(struct dm_target *ti, status_type_t type,
@ -932,8 +933,8 @@ static int __origin_write(struct list_head *snapshots, struct bio *bio)
/* Do all the snapshots on this origin */
list_for_each_entry (snap, snapshots, list) {
/* Only deal with valid snapshots */
if (!snap->valid)
/* Only deal with valid and active snapshots */
if (!snap->valid || !snap->active)
continue;
/* Nothing to do if writing beyond end of snapshot */
@ -1104,7 +1105,7 @@ static int origin_status(struct dm_target *ti, status_type_t type, char *result,
static struct target_type origin_target = {
.name = "snapshot-origin",
.version = {1, 0, 1},
.version = {1, 1, 0},
.module = THIS_MODULE,
.ctr = origin_ctr,
.dtr = origin_dtr,
@ -1115,7 +1116,7 @@ static struct target_type origin_target = {
static struct target_type snapshot_target = {
.name = "snapshot",
.version = {1, 0, 1},
.version = {1, 1, 0},
.module = THIS_MODULE,
.ctr = snapshot_ctr,
.dtr = snapshot_dtr,

4
drivers/md/dm-snap.h
View File

@ -99,7 +99,9 @@ struct dm_snapshot {
/* You can't use a snapshot if this is 0 (e.g. if full) */
int valid;
int have_metadata;
/* Origin writes don't trigger exceptions until this is set */
int active;
/* Used for display of table */
char type;