ceph: wake up 'safe' waiters when unregistering request

We also need to wake up 'safe' waiters if error occurs or request
aborted. Otherwise sync(2)/fsync(2) may hang forever.

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
Signed-off-by: Sage Weil <sage@inktank.com>
diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c
index 8ef7926..d90861f 100644
--- a/fs/ceph/mds_client.c
+++ b/fs/ceph/mds_client.c
@@ -644,6 +644,8 @@
 		req->r_unsafe_dir = NULL;
 	}
 
+	complete_all(&req->r_safe_completion);
+
 	ceph_mdsc_put_request(req);
 }
 
@@ -2186,7 +2188,6 @@
 	if (head->safe) {
 		req->r_got_safe = true;
 		__unregister_request(mdsc, req);
-		complete_all(&req->r_safe_completion);
 
 		if (req->r_got_unsafe) {
 			/*