dev_ioctl: add missing NETDEV_CHANGE_TX_QUEUE_LEN event notification

When changing dev tx_queue_len via netlink or net-sysfs,
a NETDEV_CHANGE_TX_QUEUE_LEN event notification will be
called.

But dev_ioctl missed this event notification, which could
cause no userspace notification would be sent.
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/dev_ioctl.c

@@ -303,7 +303,18 @@ static int dev_ifsioc(struct net *net, struct ifreq *ifr, unsigned int cmd)
 	case SIOCSIFTXQLEN:
 		if (ifr->ifr_qlen < 0)
 			return -EINVAL;
-		dev->tx_queue_len = ifr->ifr_qlen;
+		if (dev->tx_queue_len ^ ifr->ifr_qlen) {
+			unsigned int orig_len = dev->tx_queue_len;
+
+			dev->tx_queue_len = ifr->ifr_qlen;
+			err = call_netdevice_notifiers(
+					NETDEV_CHANGE_TX_QUEUE_LEN, dev);
+			err = notifier_to_errno(err);
+			if (err) {
+				dev->tx_queue_len = orig_len;
+				return err;
+			}
+		}
 		return 0;
 
 	case SIOCSIFNAME: