ceph: skip existing superblocks that are blocklisted or shut down when mounting

Currently when mounting, we may end up finding an existing superblock
that corresponds to a blocklisted MDS client. This means that the new
mount ends up being unusable.

If we've found an existing superblock with a client that is already
blocklisted, and the client is not configured to recover on its own,
fail the match. Ditto if the superblock has been forcibly unmounted.

While we're in here, also rename "other" to the more conventional "fsc".

Cc: stable@vger.kernel.org
URL: https://bugzilla.redhat.com/show_bug.cgi?id=1901499Signed-off-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: Xiubo Li <xiubli@redhat.com>
Reviewed-by: Ilya Dryomov <idryomov@gmail.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

fs/ceph/super.c

@@ -1002,16 +1002,16 @@ static int ceph_compare_super(struct super_block *sb, struct fs_context *fc)
 	struct ceph_fs_client *new = fc->s_fs_info;
 	struct ceph_mount_options *fsopt = new->mount_options;
 	struct ceph_options *opt = new->client->options;
-	struct ceph_fs_client *other = ceph_sb_to_client(sb);
+	struct ceph_fs_client *fsc = ceph_sb_to_client(sb);
 
 	dout("ceph_compare_super %p\n", sb);
 
-	if (compare_mount_options(fsopt, opt, other)) {
+	if (compare_mount_options(fsopt, opt, fsc)) {
 		dout("monitor(s)/mount options don't match\n");
 		return 0;
 	}
 	if ((opt->flags & CEPH_OPT_FSID) &&
-	    ceph_fsid_compare(&opt->fsid, &other->client->fsid)) {
+	    ceph_fsid_compare(&opt->fsid, &fsc->client->fsid)) {
 		dout("fsid doesn't match\n");
 		return 0;
 	}
@@ -1019,6 +1019,17 @@ static int ceph_compare_super(struct super_block *sb, struct fs_context *fc)
 		dout("flags differ\n");
 		return 0;
 	}
+
+	if (fsc->blocklisted && !ceph_test_mount_opt(fsc, CLEANRECOVER)) {
+		dout("client is blocklisted (and CLEANRECOVER is not set)\n");
+		return 0;
+	}
+
+	if (fsc->mount_state == CEPH_MOUNT_SHUTDOWN) {
+		dout("client has been forcibly unmounted\n");
+		return 0;
+	}
+
 	return 1;
 }