do_mq_notify(): switch to CLASS(fd)

The only failure exit before fdget() is a return, the only thing done
after fdput() is transposable with it.

Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Author: Al Viro

ipc/mqueue.c

@@ -1317,7 +1317,6 @@ SYSCALL_DEFINE5(mq_timedreceive, mqd_t, mqdes, char __user *, u_msg_ptr,
 static int do_mq_notify(mqd_t mqdes, const struct sigevent *notification)
 {
 	int ret;
-	struct fd f;
 	struct sock *sock;
 	struct inode *inode;
 	struct mqueue_inode_info *info;
@@ -1370,16 +1369,16 @@ static int do_mq_notify(mqd_t mqdes, const struct sigevent *notification)
 		}
 	}
 
-	f = fdget(mqdes);
-	if (!fd_file(f)) {
+	CLASS(fd, f)(mqdes);
+	if (fd_empty(f)) {
 		ret = -EBADF;
 		goto out;
 	}
 
 	inode = file_inode(fd_file(f));
 	if (unlikely(fd_file(f)->f_op != &mqueue_file_operations)) {
 		ret = -EBADF;
-		goto out_fput;
+		goto out;
 	}
 	info = MQUEUE_I(inode);
 
@@ -1418,8 +1417,6 @@ static int do_mq_notify(mqd_t mqdes, const struct sigevent *notification)
 		inode_set_atime_to_ts(inode, inode_set_ctime_current(inode));
 	}
 	spin_unlock(&info->lock);
-out_fput:
-	fdput(f);
 out:
 	if (sock)
 		netlink_detachskb(sock, nc);