i40evf: fix panic during MTU change

Down was requesting queue disables, but then exited immediately
without waiting for the queues to actually disable.  This could
allow any function called after i40evf_down to run immediately,
including i40evf_up, and causes a memory leak.

Removing the whole reinit_locked function is the best way
to go about this, and allows for the driver to handle the
state changes by requesting reset from the periodic timer.

Also, add a couple WARN_ONs in slow path to help us recognize
if we re-introduce this issue or missed any cases.

Signed-off-by: Mitch Williams <mitch.a.williams@intel.com>
Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
diff --git a/drivers/net/ethernet/intel/i40evf/i40e_txrx.c b/drivers/net/ethernet/intel/i40evf/i40e_txrx.c
index f54996f1..395f32f 100644
--- a/drivers/net/ethernet/intel/i40evf/i40e_txrx.c
+++ b/drivers/net/ethernet/intel/i40evf/i40e_txrx.c
@@ -484,6 +484,8 @@
 	if (!dev)
 		return -ENOMEM;
 
+	/* warn if we are about to overwrite the pointer */
+	WARN_ON(tx_ring->tx_bi);
 	bi_size = sizeof(struct i40e_tx_buffer) * tx_ring->count;
 	tx_ring->tx_bi = kzalloc(bi_size, GFP_KERNEL);
 	if (!tx_ring->tx_bi)
@@ -644,6 +646,8 @@
 	struct device *dev = rx_ring->dev;
 	int bi_size;
 
+	/* warn if we are about to overwrite the pointer */
+	WARN_ON(rx_ring->rx_bi);
 	bi_size = sizeof(struct i40e_rx_buffer) * rx_ring->count;
 	rx_ring->rx_bi = kzalloc(bi_size, GFP_KERNEL);
 	if (!rx_ring->rx_bi)