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: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
diff --git a/drivers/md/dm-snap.c b/drivers/md/dm-snap.c
index 59d9ef6..23e3396 100644
--- a/drivers/md/dm-snap.c
+++ b/drivers/md/dm-snap.c
@@ -709,7 +709,8 @@
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 @@
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 @@
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 @@
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 @@
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);