n_hdlc: simplify freeing of buffer list

n_hdlc_release contains four loops to free each buffer list. Create a
helper (n_hdlc_free_buf_list) and call it for every list instead. It
makes n_hdlc_release more readable.

We are switching from "for (;;)" to "do {} while (buf)" which avoids the
"if (buf)" completely -- kfree is a nop for NULL pointers.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20200219084118.26491-7-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/n_hdlc.c b/drivers/tty/n_hdlc.c
index a713a98..07ba42b 100644 (file)
--- a/drivers/tty/n_hdlc.c
+++ b/drivers/tty/n_hdlc.c
@@ -215,6 +215,16 @@ static struct tty_ldisc_ops n_hdlc_ldisc = {
        .flush_buffer   = flush_rx_queue,
 };
 
+static void n_hdlc_free_buf_list(struct n_hdlc_buf_list *list)
+{
+       struct n_hdlc_buf *buf;
+
+       do {
+               buf = n_hdlc_buf_get(list);
+               kfree(buf);
+       } while (buf);
+}
+
 /**
  * n_hdlc_release - release an n_hdlc per device line discipline info structure
  * @n_hdlc - per device line discipline info structure
@@ -222,7 +232,6 @@ static struct tty_ldisc_ops n_hdlc_ldisc = {
 static void n_hdlc_release(struct n_hdlc *n_hdlc)
 {
        struct tty_struct *tty = n_hdlc2tty (n_hdlc);
-       struct n_hdlc_buf *buf;
 
        /* Ensure that the n_hdlcd process is not hanging on select()/poll() */
        wake_up_interruptible (&tty->read_wait);
@@ -231,37 +240,11 @@ static void n_hdlc_release(struct n_hdlc *n_hdlc)
        if (tty->disc_data == n_hdlc)
                tty->disc_data = NULL;  /* Break the tty->n_hdlc link */
 
-       /* Release transmit and receive buffers */
-       for(;;) {
-               buf = n_hdlc_buf_get(&n_hdlc->rx_free_buf_list);
-               if (buf) {
-                       kfree(buf);
-               } else
-                       break;
-       }
-       for(;;) {
-               buf = n_hdlc_buf_get(&n_hdlc->tx_free_buf_list);
-               if (buf) {
-                       kfree(buf);
-               } else
-                       break;
-       }
-       for(;;) {
-               buf = n_hdlc_buf_get(&n_hdlc->rx_buf_list);
-               if (buf) {
-                       kfree(buf);
-               } else
-                       break;
-       }
-       for(;;) {
-               buf = n_hdlc_buf_get(&n_hdlc->tx_buf_list);
-               if (buf) {
-                       kfree(buf);
-               } else
-                       break;
-       }
+       n_hdlc_free_buf_list(&n_hdlc->rx_free_buf_list);
+       n_hdlc_free_buf_list(&n_hdlc->tx_free_buf_list);
+       n_hdlc_free_buf_list(&n_hdlc->rx_buf_list);
+       n_hdlc_free_buf_list(&n_hdlc->tx_buf_list);
        kfree(n_hdlc);
-       
 }      /* end of n_hdlc_release() */
 
 /**