ceph: fail the request if the peer MDS doesn't support getvxattr op

Just fail the request instead sending the request out, or the peer
MDS will crash.

Link: https://tracker.ceph.com/issues/56529
Signed-off-by: Xiubo Li <[e-mail]>
Signed-off-by: Ilya Dryomov <[e-mail]>

fs/ceph/inode.c

···
 		goto out;
 	}
 
+	req->r_feature_needed = CEPHFS_FEATURE_OP_GETVXATTR;
 	req->r_path2 = kstrdup(name, GFP_NOFS);
 	if (!req->r_path2) {
 		err = -ENOMEM;

fs/ceph/mds_client.c

···
 	INIT_LIST_HEAD(&req->r_unsafe_dir_item);
 	INIT_LIST_HEAD(&req->r_unsafe_target_item);
 	req->r_fmode = -1;
+	req->r_feature_needed = -1;
 	kref_init(&req->r_kref);
 	RB_CLEAR_NODE(&req->r_node);
 	INIT_LIST_HEAD(&req->r_wait);
···
 
 	dout("do_request mds%d session %p state %s\n", mds, session,
 	     ceph_session_state_name(session->s_state));
+
+	/*
+	 * The old ceph will crash the MDSs when see unknown OPs
+	 */
+	if (req->r_feature_needed > 0 &&
+	    !test_bit(req->r_feature_needed, &session->s_features)) {
+		err = -EOPNOTSUPP;
+		goto out_session;
+	}
+
 	if (session->s_state != CEPH_MDS_SESSION_OPEN &&
 	    session->s_state != CEPH_MDS_SESSION_HUNG) {
 		/*

fs/ceph/mds_client.h

···
 	CEPHFS_FEATURE_METRIC_COLLECT,
 	CEPHFS_FEATURE_ALTERNATE_NAME,
 	CEPHFS_FEATURE_NOTIFY_SESSION_STATE,
+	CEPHFS_FEATURE_OP_GETVXATTR,
 
-	CEPHFS_FEATURE_MAX = CEPHFS_FEATURE_NOTIFY_SESSION_STATE,
+	CEPHFS_FEATURE_MAX = CEPHFS_FEATURE_OP_GETVXATTR,
 };
 
 #define CEPHFS_FEATURES_CLIENT_SUPPORTED {	\
···
 	CEPHFS_FEATURE_DELEG_INO,		\
 	CEPHFS_FEATURE_METRIC_COLLECT,		\
 	CEPHFS_FEATURE_NOTIFY_SESSION_STATE,	\
+	CEPHFS_FEATURE_OP_GETVXATTR,		\
 }
 
 /*
···
 	long long	  r_dir_release_cnt;
 	long long	  r_dir_ordered_cnt;
 	int		  r_readdir_cache_idx;
+
+	int		  r_feature_needed;
 
 	struct ceph_cap_reservation r_caps_reservation;
 };