ceph: re-send requests when MDS enters reconnecting stage

So that MDS can check if any request is already completed and process
completed requests in clientreplay stage. When completed requests are
processed in clientreplay stage, MDS can avoid sending traceless
replies.
Signed-off-by: Yan, Zheng <zyan@redhat.com>

fs/ceph/mds_client.c

@@ -2184,6 +2184,8 @@ static void kick_requests(struct ceph_mds_client *mdsc, int mds)
 		p = rb_next(p);
 		if (req->r_got_unsafe)
 			continue;
+		if (req->r_attempts > 0)
+			continue; /* only new requests */
 		if (req->r_session &&
 		    req->r_session->s_mds == mds) {
 			dout(" kicking tid %llu\n", req->r_tid);
@@ -2517,6 +2519,7 @@ static void handle_forward(struct ceph_mds_client *mdsc,
 		dout("forward tid %llu to mds%d (we resend)\n", tid, next_mds);
 		BUG_ON(req->r_err);
 		BUG_ON(req->r_got_result);
+		req->r_attempts = 0;
 		req->r_num_fwd = fwd_seq;
 		req->r_resend_mds = next_mds;
 		put_request_session(req);
@@ -2648,6 +2651,7 @@ static void replay_unsafe_requests(struct ceph_mds_client *mdsc,
 				   struct ceph_mds_session *session)
 {
 	struct ceph_mds_request *req, *nreq;
+	struct rb_node *p;
 	int err;
 
 	dout("replay_unsafe_requests mds%d\n", session->s_mds);
@@ -2660,6 +2664,28 @@ static void replay_unsafe_requests(struct ceph_mds_client *mdsc,
 			ceph_con_send(&session->s_con, req->r_request);
 		}
 	}
+
+	/*
+	 * also re-send old requests when MDS enters reconnect stage. So that MDS
+	 * can process completed request in clientreplay stage.
+	 */
+	p = rb_first(&mdsc->request_tree);
+	while (p) {
+		req = rb_entry(p, struct ceph_mds_request, r_node);
+		p = rb_next(p);
+		if (req->r_got_unsafe)
+			continue;
+		if (req->r_attempts == 0)
+			continue; /* only old requests */
+		if (req->r_session &&
+		    req->r_session->s_mds == session->s_mds) {
+			err = __prepare_send_request(mdsc, req, session->s_mds);
+			if (!err) {
+				ceph_msg_get(req->r_request);
+				ceph_con_send(&session->s_con, req->r_request);
+			}
+		}
+	}
 	mutex_unlock(&mdsc->mutex);
 }
 
@@ -2977,9 +3003,6 @@ static void check_new_map(struct ceph_mds_client *mdsc,
 				mutex_unlock(&s->s_mutex);
 				s->s_state = CEPH_MDS_SESSION_RESTARTING;
 			}
-
-			/* kick any requests waiting on the recovering mds */
-			kick_requests(mdsc, i);
 		} else if (oldstate == newstate) {
 			continue;  /* nothing new with this mds */
 		}