usbnet: Stop RX Q on MTU change

When MTU is changed unlink_urbs() flushes RX Q but mean while usbnet_bh()
can fill up the Q at the same time.
Depends on which HCD is down there unlink takes long time then the flush
never ends.

Signed-off-by: Soohoon Lee <soohoon.lee@f5.com>
Reviewed-by: Kimball Murray <kmurray@f5.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/usb/usbnet.c

@@ -395,8 +395,11 @@ int usbnet_change_mtu (struct net_device *net, int new_mtu)
 	dev->hard_mtu = net->mtu + net->hard_header_len;
 	if (dev->rx_urb_size == old_hard_mtu) {
 		dev->rx_urb_size = dev->hard_mtu;
-		if (dev->rx_urb_size > old_rx_urb_size)
+		if (dev->rx_urb_size > old_rx_urb_size) {
+			usbnet_pause_rx(dev);
 			usbnet_unlink_rx_urbs(dev);
+			usbnet_resume_rx(dev);
+		}
 	}
 
 	/* max qlen depend on hard_mtu and rx_urb_size */
@@ -1508,8 +1511,9 @@ static void usbnet_bh (unsigned long param)
 	} else if (netif_running (dev->net) &&
 		   netif_device_present (dev->net) &&
 		   netif_carrier_ok(dev->net) &&
-		   !timer_pending (&dev->delay) &&
-		   !test_bit (EVENT_RX_HALT, &dev->flags)) {
+		   !timer_pending(&dev->delay) &&
+		   !test_bit(EVENT_RX_PAUSED, &dev->flags) &&
+		   !test_bit(EVENT_RX_HALT, &dev->flags)) {
 		int	temp = dev->rxq.qlen;
 
 		if (temp < RX_QLEN(dev)) {