diff --git a/fs/ceph/addr.c b/fs/ceph/addr.c
index 2362f2591..3465ff95c 100755
--- a/fs/ceph/addr.c
+++ b/fs/ceph/addr.c
@@ -91,6 +91,7 @@ static int ceph_set_page_dirty(struct page *page)
 
 	/* dirty the head */
 	spin_lock(&ci->i_ceph_lock);
+	BUG_ON(ci->i_wr_ref == 0); // caller should hold Fw reference
 	if (__ceph_have_pending_cap_snap(ci)) {
 		struct ceph_cap_snap *capsnap =
 				list_last_entry(&ci->i_cap_snaps,