ceph: don't rely on error_string to validate blocklisted session.

The "error_string" in the metadata of MClientSession is being
parsed by kclient to validate whether the session is blocklisted.
The "error_string" is for humans and shouldn't be relied on it.
Hence added the flag to MClientsession to indicate the session
is blocklisted.

[ jlayton: minor formatting cleanup ]

URL: https://tracker.ceph.com/issues/47450
Signed-off-by: Kotresh HR <[email protected]>
Signed-off-by: Jeff Layton <[email protected]>
Signed-off-by: Ilya Dryomov <[email protected]>

Author: kotreshhr

fs/ceph/mds_client.c

@@ -3361,9 +3361,14 @@ static void handle_session(struct ceph_mds_session *session,
 
 	if (msg_version >= 3) {
 		u32 len;
-		/* version >= 2, metadata */
-		if (__decode_session_metadata(&p, end, &blocklisted) < 0)
+		/* version >= 2 and < 5, decode metadata, skip otherwise
+		 * as it's handled via flags.
+		 */
+		if (msg_version >= 5)
+			ceph_decode_skip_map(&p, end, string, string, bad);
+		else if (__decode_session_metadata(&p, end, &blocklisted) < 0)
 			goto bad;
+
 		/* version >= 3, feature bits */
 		ceph_decode_32_safe(&p, end, len, bad);
 		if (len) {
@@ -3372,6 +3377,18 @@ static void handle_session(struct ceph_mds_session *session,
 		}
 	}
 
+	if (msg_version >= 5) {
+		u32 flags;
+		/* version >= 4, struct_v, struct_cv, len, metric_spec */
+	        ceph_decode_skip_n(&p, end, 2 + sizeof(u32) * 2, bad);
+		/* version >= 5, flags   */
+                ceph_decode_32_safe(&p, end, flags, bad);
+		if (flags & CEPH_SESSION_BLOCKLISTED) {
+		        pr_warn("mds%d session blocklisted\n", session->s_mds);
+			blocklisted = true;
+		}
+	}
+
 	mutex_lock(&mdsc->mutex);
 	if (op == CEPH_SESSION_CLOSE) {
 		ceph_get_mds_session(session);

include/linux/ceph/ceph_fs.h

@@ -302,6 +302,8 @@ enum {
 	CEPH_SESSION_REQUEST_FLUSH_MDLOG,
 };
 
+#define CEPH_SESSION_BLOCKLISTED	(1 << 0)  /* session blocklisted */
+
 extern const char *ceph_session_op_name(int op);
 
 struct ceph_mds_session_head {