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dm snapshot: support barriers in snapshot merge target

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Sets num_flush_requests=2 to support flushing both the origin and cow
devices used by the snapshot-merge target.

Also, snapshot_ctr() now gets the origin device using FMODE_WRITE if the
target is snapshot-merge (which writes to the origin device).

Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
This commit is contained in:
Mike Snitzer 2009-12-10 23:52:31 +00:00 committed by Alasdair G Kergon
parent 3452c2a1eb
commit 10b8106a70
1 changed files with 18 additions and 3 deletions
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21
drivers/md/dm-snap.c
View file

@ -709,7 +709,8 @@ static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv)
int i;
int r = -EINVAL;
char *origin_path, *cow_path;
unsigned args_used;
unsigned args_used, num_flush_requests = 1;
fmode_t origin_mode = FMODE_READ;
if (argc != 4) {
ti->error = "requires exactly 4 arguments";
@ -717,6 +718,11 @@ static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv)
goto bad;
}
if (dm_target_is_snapshot_merge(ti)) {
num_flush_requests = 2;
origin_mode = FMODE_WRITE;
}
origin_path = argv[0];
argv++;
argc--;
@ -750,7 +756,7 @@ static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv)
argv += args_used;
argc -= args_used;
r = dm_get_device(ti, origin_path, 0, ti->len, FMODE_READ, &s->origin);
r = dm_get_device(ti, origin_path, 0, ti->len, origin_mode, &s->origin);
if (r) {
ti->error = "Cannot get origin device";
goto bad_origin;
@ -801,7 +807,7 @@ static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv)
INIT_WORK(&s->queued_bios_work, flush_queued_bios);
ti->private = s;
ti->num_flush_requests = 1;
ti->num_flush_requests = num_flush_requests;
/* Add snapshot to the list of snapshots for this origin */
/* Exceptions aren't triggered till snapshot_resume() is called */
@ -1326,6 +1332,15 @@ static int snapshot_merge_map(struct dm_target *ti, struct bio *bio,
int r = DM_MAPIO_REMAPPED;
chunk_t chunk;
if (unlikely(bio_empty_barrier(bio))) {
if (!map_context->flush_request)
bio->bi_bdev = s->origin->bdev;
else
bio->bi_bdev = s->cow->bdev;
map_context->ptr = NULL;
return DM_MAPIO_REMAPPED;
}
chunk = sector_to_chunk(s->store, bio->bi_sector);
down_read(&s->lock);