diff options
| author | Mike Snitzer | 2019-07-17 11:12:30 -0400 |
|---|---|---|
| committer | Mike Snitzer | 2019-07-17 11:12:30 -0400 |
| commit | 3ee25485ba8e8271fe9401eef5003c20ab648ddf (patch) | |
| tree | ba1c9bde48555434b3343143d2f84fcf8770c037 /drivers/md | |
| parent | 3b8cafdd5436f9298b3bf6eb831df5eef5ee82b6 (diff) | |
dm snapshot: fix oversights in optional discard support
__find_snapshots_sharing_cow() should always be used with _origins_lock
held so fix snapshot_io_hints() accordingly. Also, once a snapshot is
being merged discards must not be allowed -- otherwise incorrect or
duplicate work will be performed.
Fixes: 2e6023850e177d ("dm snapshot: add optional discard support features")
Reported-by: Nikos Tsironis <ntsironis@arrikto.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Diffstat (limited to 'drivers/md')
| -rw-r--r-- | drivers/md/dm-snap.c | 10 |
1 files changed, 10 insertions, 0 deletions
diff --git a/drivers/md/dm-snap.c b/drivers/md/dm-snap.c index 63916e1dc569..f150f5c5492b 100644 --- a/drivers/md/dm-snap.c +++ b/drivers/md/dm-snap.c @@ -2072,6 +2072,12 @@ static int snapshot_merge_map(struct dm_target *ti, struct bio *bio) return DM_MAPIO_REMAPPED; } + if (unlikely(bio_op(bio) == REQ_OP_DISCARD)) { + /* Once merging, discards no longer effect change */ + bio_endio(bio); + return DM_MAPIO_SUBMITTED; + } + chunk = sector_to_chunk(s->store, bio->bi_iter.bi_sector); down_write(&s->lock); @@ -2331,6 +2337,8 @@ static void snapshot_io_hints(struct dm_target *ti, struct queue_limits *limits) if (snap->discard_zeroes_cow) { struct dm_snapshot *snap_src = NULL, *snap_dest = NULL; + down_read(&_origins_lock); + (void) __find_snapshots_sharing_cow(snap, &snap_src, &snap_dest, NULL); if (snap_src && snap_dest) snap = snap_src; @@ -2338,6 +2346,8 @@ static void snapshot_io_hints(struct dm_target *ti, struct queue_limits *limits) /* All discards are split on chunk_size boundary */ limits->discard_granularity = snap->store->chunk_size; limits->max_discard_sectors = snap->store->chunk_size; + + up_read(&_origins_lock); } } |