e1000e: flow control thresholds not correct when changing mtu

When changing MTU, save it off prior to resetting otherwise the flow control
thresholds may be miscalculated.

Signed-off-by: Bruce Allan <bruce.w.allan@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/e1000e/netdev.c

@@ -4305,8 +4305,10 @@ static int e1000_change_mtu(struct net_device *netdev, int new_mtu)
 
 	while (test_and_set_bit(__E1000_RESETTING, &adapter->state))
 		msleep(1);
-	/* e1000e_down has a dependency on max_frame_size */
+	/* e1000e_down -> e1000e_reset dependent on max_frame_size & mtu */
 	adapter->max_frame_size = max_frame;
+	e_info("changing MTU from %d to %d\n", netdev->mtu, new_mtu);
+	netdev->mtu = new_mtu;
 	if (netif_running(netdev))
 		e1000e_down(adapter);
 
@@ -4336,9 +4338,6 @@ static int e1000_change_mtu(struct net_device *netdev, int new_mtu)
 		adapter->rx_buffer_len = ETH_FRAME_LEN + VLAN_HLEN
 					 + ETH_FCS_LEN;
 
-	e_info("changing MTU from %d to %d\n", netdev->mtu, new_mtu);
-	netdev->mtu = new_mtu;
-
 	if (netif_running(netdev))
 		e1000e_up(adapter);
 	else