ibmvnic: Properly dispose of all skbs during a failover.

During a reset, there may have been transmits in flight that are no
longer valid and cannot be fulfilled. Resetting and clearing the
queues is insufficient; each skb also needs to be explicitly freed
so that upper levels are not left waiting for confirmation of a
transmit that will never happen. If this happens frequently enough,
the apparent backlog will cause TCP to begin "congestion control"
unnecessarily, culminating in permanently decreased throughput.

Fixes: d7c0ef36bde03 ("ibmvnic: Free and re-allocate scrqs when tx/rx scrqs change")
Tested-by: Nick Child <[e-mail]>
Reviewed-by: Brian King <[e-mail]>
Signed-off-by: Rick Lindsley <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

drivers/net/ethernet/ibm/ibmvnic.c

···
 			release_sub_crqs(adapter, 0);
 			rc = init_sub_crqs(adapter);
 		} else {
+			/* no need to reinitialize completely, but we do
+			 * need to clean up transmits that were in flight
+			 * when we processed the reset.  Failure to do so
+			 * will confound the upper layer, usually TCP, by
+			 * creating the illusion of transmits that are
+			 * awaiting completion.
+			 */
+			clean_tx_pools(adapter);
+
 			rc = reset_sub_crq_queues(adapter);
 		}
 	} else {