dm snapshot: delay merging a chunk until writes to it complete

Track writes to chunks that are currently being merged and delay merging
a chunk until all writes to that chunk finish.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Reviewed-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

1 files changed, 5 insertions, 1 deletions

diff --git a/drivers/md/dm-snap.c b/drivers/md/dm-snap.c
index 91a47c522b09..bc52776c69cc 100644
--- a/drivers/md/dm-snap.c
+++ b/drivers/md/dm-snap.c
@@ -892,7 +892,7 @@ static void snapshot_merge_next_chunks(struct dm_snapshot *s)
         s->num_merging_chunks = 1;
         up_write(&s->lock);
 
-        /* !!! FIXME: wait until writes to this chunk drain */
+        __check_for_conflicting_io(s, old_chunk);
 
         dm_kcopyd_copy(s->kcopyd_client, &src, 1, &dest, 0, merge_callback, s);
         return;
@@ -1635,7 +1635,11 @@ static int snapshot_merge_map(struct dm_target *ti, struct bio *bio,
                         r = DM_MAPIO_SUBMITTED;
                         goto out_unlock;
                 }
+
                 remap_exception(s, e, bio, chunk);
+
+                if (bio_rw(bio) == WRITE)
+                        map_context->ptr = track_chunk(s, chunk);
                 goto out_unlock;
         }