ceph: add session already open notify support

If the connection was accidently closed due to the socket issue or
something else the clients will try to open the opened sessions, the
MDSes will send the session open reply one more time if the clients
support the notify feature.

When the clients retry to open the sessions the s_seq will be 0 as
default, we need to update it anyway.

Link: https://tracker.ceph.com/issues/53911Signed-off-by: Xiubo Li <xiubli@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

fs/ceph/mds_client.c

@@ -3540,11 +3540,26 @@ static void handle_session(struct ceph_mds_session *session,
 	case CEPH_SESSION_OPEN:
 		if (session->s_state == CEPH_MDS_SESSION_RECONNECTING)
 			pr_info("mds%d reconnect success\n", session->s_mds);
-		session->s_state = CEPH_MDS_SESSION_OPEN;
-		session->s_features = features;
-		renewed_caps(mdsc, session, 0);
-		if (test_bit(CEPHFS_FEATURE_METRIC_COLLECT, &session->s_features))
-			metric_schedule_delayed(&mdsc->metric);
+
+		if (session->s_state == CEPH_MDS_SESSION_OPEN) {
+			pr_notice("mds%d is already opened\n", session->s_mds);
+		} else {
+			session->s_state = CEPH_MDS_SESSION_OPEN;
+			session->s_features = features;
+			renewed_caps(mdsc, session, 0);
+			if (test_bit(CEPHFS_FEATURE_METRIC_COLLECT,
+				     &session->s_features))
+				metric_schedule_delayed(&mdsc->metric);
+		}
+
+		/*
+		 * The connection maybe broken and the session in client
+		 * side has been reinitialized, need to update the seq
+		 * anyway.
+		 */
+		if (!session->s_seq && seq)
+			session->s_seq = seq;
+
 		wake = 1;
 		if (mdsc->stopping)
 			__close_session(mdsc, session);

fs/ceph/mds_client.h

@@ -29,8 +29,10 @@ enum ceph_feature_type {
 	CEPHFS_FEATURE_MULTI_RECONNECT,
 	CEPHFS_FEATURE_DELEG_INO,
 	CEPHFS_FEATURE_METRIC_COLLECT,
+	CEPHFS_FEATURE_ALTERNATE_NAME,
+	CEPHFS_FEATURE_NOTIFY_SESSION_STATE,
 
-	CEPHFS_FEATURE_MAX = CEPHFS_FEATURE_METRIC_COLLECT,
+	CEPHFS_FEATURE_MAX = CEPHFS_FEATURE_NOTIFY_SESSION_STATE,
 };
 
 #define CEPHFS_FEATURES_CLIENT_SUPPORTED {	\
@@ -41,6 +43,7 @@ enum ceph_feature_type {
 	CEPHFS_FEATURE_MULTI_RECONNECT,		\
 	CEPHFS_FEATURE_DELEG_INO,		\
 	CEPHFS_FEATURE_METRIC_COLLECT,		\
+	CEPHFS_FEATURE_NOTIFY_SESSION_STATE,	\
 }
 
 /*