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Subject: [dm-devel] [PATCH v3 10/12] dm snapshot: make exceptions if merge
	is dispatching to origin
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diff --git a/drivers/md/dm-snap.c b/drivers/md/dm-snap.c
index 2ded8ee..5b2d0f4 100644
--- a/drivers/md/dm-snap.c
+++ b/drivers/md/dm-snap.c
@@ -1550,6 +1550,11 @@ static int snapshot_merge_map(struct dm_target *ti, struct bio *bio,
 
 	bio->bi_bdev = s->origin->bdev;
 
+	if (bio_rw(bio) == WRITE) {
+		up_write(&s->lock);
+		return do_origin(s->origin, bio);
+	}
+
  out_unlock:
 	up_write(&s->lock);