tty: n_tty: move more_to_be_read to the end of n_tty_read()

n_tty_read() contains "we need more data" handling deep in that
function. And there is also a label (more_to_be_read) as we handle this
situation from two places.

It makes more sense to have all "return"s accumulated at the end of
functions. And "goto" from multiple places there. Therefore, do this
with the "more_to_be_read" label in n_tty_read().

After this and the previous changes, n_tty_read() is now much more
easier to follow.

Signed-off-by: Jiri Slaby (SUSE) <jirislaby@kernel.org>
Link: https://lore.kernel.org/r/20250317070046.24386-12-jirislaby@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: Jiri Slaby (SUSE)

drivers/tty/n_tty.c

@@ -2281,21 +2281,8 @@ static ssize_t n_tty_read(struct tty_struct *tty, struct file *file, u8 *kbuf,
 				nr--;
 			}
 
-			/*
-			 * Copy data, and if there is more to be had
-			 * and we have nothing more to wait for, then
-			 * let's mark us for retries.
-			 *
-			 * NOTE! We return here with both the termios_sem
-			 * and atomic_read_lock still held, the retries
-			 * will release them when done.
-			 */
-			if (copy_from_read_buf(tty, &kb, &nr) && kb - kbuf >= minimum) {
-more_to_be_read:
-				remove_wait_queue(&tty->read_wait, &wait);
-				*cookie = cookie;
-				return kb - kbuf;
-			}
+			if (copy_from_read_buf(tty, &kb, &nr) && kb - kbuf >= minimum)
+				goto more_to_be_read;
 		}
 
 		n_tty_check_unthrottle(tty);
@@ -2322,6 +2309,18 @@ static ssize_t n_tty_read(struct tty_struct *tty, struct file *file, u8 *kbuf,
 		retval = kb - kbuf;
 
 	return retval;
+more_to_be_read:
+	/*
+	 * There is more to be had and we have nothing more to wait for, so
+	 * let's mark us for retries.
+	 *
+	 * NOTE! We return here with both the termios_sem and atomic_read_lock
+	 * still held, the retries will release them when done.
+	 */
+	remove_wait_queue(&tty->read_wait, &wait);
+	*cookie = cookie;
+
+	return kb - kbuf;
 }
 
 /**