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Commit 10b8106a authored by Mike Snitzer's avatar Mike Snitzer Committed by Alasdair G Kergon
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dm snapshot: support barriers in snapshot merge target 



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: default avatarMike Snitzer <snitzer@redhat.com>
Signed-off-by: default avatarAlasdair G Kergon <agk@redhat.com>
parent 3452c2a1

drivers/md/dm-snap.c

+18 −3
Original line number Diff line number Diff line
@@ -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);