[PATCH v4 10/13] dm snapshot: do not merge a chunk until active writes to it finish

[Mike Snitzer <snitzer@redhat.com>]

From: Mikulas Patocka <mpatocka@redhat.com>

Track merging snapshot device's in-progress writes, to chunks that
were already remapped, 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>
---
 drivers/md/dm-snap.c |    7 ++++++-
 1 files changed, 6 insertions(+), 1 deletions(-)

diff --git a/drivers/md/dm-snap.c b/drivers/md/dm-snap.c
index e1ec4c4..e41be70 100644
--- a/drivers/md/dm-snap.c
+++ b/drivers/md/dm-snap.c
@@ -784,7 +784,8 @@ static void snapshot_merge_process(struct dm_snapshot *s)
 	s->merge_write_interlock_n = 1;
 	up_write(&s->lock);
 
-	/* !!! FIXME: wait until writes to this chunk drain */
+	while (__chunk_is_tracked(s, old_chunk))
+		msleep(1);
 
 	dm_kcopyd_copy(s->kcopyd_client, &src, 1, &dest, 0, merge_callback, s);
 	return;
@@ -1542,7 +1543,11 @@ 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;
 	}
 
-- 
1.6.5.2