ceph: check if file lock exists before sending unlock request

When a process exits, kernel closes its files. locks_remove_file()
is called to remove file locks on these files. locks_remove_file()
tries unlocking files even there is no file lock.
Signed-off-by: "Yan, Zheng" <zyan@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

fs/ceph/locks.c

@@ -210,6 +210,21 @@ static int ceph_lock_wait_for_completion(struct ceph_mds_client *mdsc,
 	return 0;
 }
 
+static int try_unlock_file(struct file *file, struct file_lock *fl)
+{
+	int err;
+	unsigned int orig_flags = fl->fl_flags;
+	fl->fl_flags |= FL_EXISTS;
+	err = locks_lock_file_wait(file, fl);
+	fl->fl_flags = orig_flags;
+	if (err == -ENOENT) {
+		if (!(orig_flags & FL_EXISTS))
+			err = 0;
+		return err;
+	}
+	return 1;
+}
+
 /**
  * Attempt to set an fcntl lock.
  * For now, this just goes away to the server. Later it may be more awesome.
@@ -255,9 +270,15 @@ int ceph_lock(struct file *file, int cmd, struct file_lock *fl)
 	else
 		lock_cmd = CEPH_LOCK_UNLOCK;
 
+	if (op == CEPH_MDS_OP_SETFILELOCK && F_UNLCK == fl->fl_type) {
+		err = try_unlock_file(file, fl);
+		if (err <= 0)
+			return err;
+	}
+
 	err = ceph_lock_message(CEPH_LOCK_FCNTL, op, inode, lock_cmd, wait, fl);
 	if (!err) {
-		if (op == CEPH_MDS_OP_SETFILELOCK) {
+		if (op == CEPH_MDS_OP_SETFILELOCK && F_UNLCK != fl->fl_type) {
 			dout("mds locked, locking locally\n");
 			err = posix_lock_file(file, fl, NULL);
 			if (err) {
@@ -311,9 +332,15 @@ int ceph_flock(struct file *file, int cmd, struct file_lock *fl)
 	else
 		lock_cmd = CEPH_LOCK_UNLOCK;
 
+	if (F_UNLCK == fl->fl_type) {
+		err = try_unlock_file(file, fl);
+		if (err <= 0)
+			return err;
+	}
+
 	err = ceph_lock_message(CEPH_LOCK_FLOCK, CEPH_MDS_OP_SETFILELOCK,
 				inode, lock_cmd, wait, fl);
-	if (!err) {
+	if (!err && F_UNLCK != fl->fl_type) {
 		err = locks_lock_file_wait(file, fl);
 		if (err) {
 			ceph_lock_message(CEPH_LOCK_FLOCK,