From: Mikulas Patocka 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 Signed-off-by: Alasdair G Kergon --- drivers/md/dm-snap.c | 11 +++++++++++ 1 file changed, 11 insertions(+) Index: linux-2.6.30/drivers/md/dm-snap.c =================================================================== --- linux-2.6.30.orig/drivers/md/dm-snap.c +++ linux-2.6.30/drivers/md/dm-snap.c @@ -678,6 +678,7 @@ static int snapshot_ctr(struct dm_target ti->private = s; ti->split_io = s->store->chunk_size; + ti->num_flush_requests = 1; return 0; @@ -1030,6 +1031,11 @@ static int snapshot_map(struct dm_target 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 @@ static int origin_ctr(struct dm_target * } ti->private = dev; + ti->num_flush_requests = 1; + return 0; } @@ -1353,6 +1361,9 @@ static int origin_map(struct dm_target * 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; }