ceph: reconnect connection if session hang in opening state

If client mds session is evicted in CEPH_MDS_SESSION_OPENING state,
mds won't send session msg to client, and delayed_work skip
CEPH_MDS_SESSION_OPENING state session, the session hang forever.

Allow ceph_con_keepalive to reconnect a session in OPENING to avoid
session hang. Also, ensure that we skip sessions in RESTARTING and
REJECTED states since those states can't be resurrected by issuing
a keepalive.

Link: https://tracker.ceph.com/issues/41551
Signed-off-by: Erqi Chen chenerqi@gmail.com
Reviewed-by: "Yan, Zheng" <zyan@redhat.com>
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

fs/ceph/mds_client.c

@@ -4088,7 +4088,9 @@ static void delayed_work(struct work_struct *work)
 				pr_info("mds%d hung\n", s->s_mds);
 			}
 		}
-		if (s->s_state < CEPH_MDS_SESSION_OPEN) {
+		if (s->s_state == CEPH_MDS_SESSION_NEW ||
+		    s->s_state == CEPH_MDS_SESSION_RESTARTING ||
+		    s->s_state == CEPH_MDS_SESSION_REJECTED) {
 			/* this mds is failed or recovering, just wait */
 			ceph_put_mds_session(s);
 			continue;