dm snapshot: support barriers
Flush support for dm-snapshot target.
This patch just forwards the flush request to either the origin or the snapshot
device. (It doesn't flush exception store metadata.)
Signed-off-by: Mikulas Patocka <mpatocka@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 d73f17f..d573165 100644
--- a/drivers/md/dm-snap.c
+++ b/drivers/md/dm-snap.c
@@ -678,6 +678,7 @@
ti->private = s;
ti->split_io = s->store->chunk_size;
+ ti->num_flush_requests = 1;
return 0;
@@ -1030,6 +1031,11 @@
chunk_t chunk;
struct dm_snap_pending_exception *pe = NULL;
+ if (unlikely(bio_empty_barrier(bio))) {
+ bio->bi_bdev = s->store->cow->bdev;
+ return DM_MAPIO_REMAPPED;
+ }
+
chunk = sector_to_chunk(s->store, bio->bi_sector);
/* Full snapshots are not usable */
@@ -1338,6 +1344,8 @@
}
ti->private = dev;
+ ti->num_flush_requests = 1;
+
return 0;
}
@@ -1353,6 +1361,9 @@
struct dm_dev *dev = ti->private;
bio->bi_bdev = dev->bdev;
+ if (unlikely(bio_empty_barrier(bio)))
+ return DM_MAPIO_REMAPPED;
+
/* Only tell snapshots if this is a write */
return (bio_rw(bio) == WRITE) ? do_origin(dev, bio) : DM_MAPIO_REMAPPED;
}