dm exception store: move cow pointer

Move COW device from snapshot to exception store.

Signed-off-by: Jonathan Brassow <jbrassow@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
diff --git a/drivers/md/dm-exception-store.c b/drivers/md/dm-exception-store.c
index 59c949b..2078b92 100644
--- a/drivers/md/dm-exception-store.c
+++ b/drivers/md/dm-exception-store.c
@@ -139,7 +139,7 @@
 
 int dm_exception_store_create(const char *type_name, struct dm_target *ti,
 			      chunk_t chunk_size, chunk_t chunk_mask,
-			      chunk_t chunk_shift,
+			      chunk_t chunk_shift, struct dm_dev *cow,
 			      struct dm_exception_store **store)
 {
 	int r = 0;
@@ -163,6 +163,8 @@
 	tmp_store->chunk_mask = chunk_mask;
 	tmp_store->chunk_shift = chunk_shift;
 
+	tmp_store->cow = cow;
+
 	r = type->ctr(tmp_store, 0, NULL);
 	if (r) {
 		put_type(type);