ixgbevf: Protect ixgbevf_down with __IXGBEVF_DOWN bit

The ixgbevf_down function can now prevent multiple executions by
doing test_and_set_bit on __IXGBEVF_DOWN. This did not work before
introduction of the __IXGBEVF_REMOVING bit, because of overloading
of __IXGBEVF_DOWN. Also add smp_mb__before_clear_bit call before
clearing the __IXGBEVF_DOWN bit.
Signed-off-by: Mark Rustad <mark.d.rustad@intel.com>
Tested-by: Phil Schmitt <phillip.j.schmitt@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.c

@@ -1620,6 +1620,7 @@ static void ixgbevf_up_complete(struct ixgbevf_adapter *adapter)
 
 	spin_unlock_bh(&adapter->mbx_lock);
 
+	smp_mb__before_clear_bit();
 	clear_bit(__IXGBEVF_DOWN, &adapter->state);
 	ixgbevf_napi_enable_all(adapter);
 
@@ -1744,7 +1745,8 @@ void ixgbevf_down(struct ixgbevf_adapter *adapter)
 	int i;
 
 	/* signal that we are down to the interrupt handler */
-	set_bit(__IXGBEVF_DOWN, &adapter->state);
+	if (test_and_set_bit(__IXGBEVF_DOWN, &adapter->state))
+		return; /* do nothing if already down */
 
 	/* disable all enabled rx queues */
 	for (i = 0; i < adapter->num_rx_queues; i++)