From c0a06ee185f2b785c7bd44c4fb6fcae80f7d1a54 Mon Sep 17 00:00:00 2001
From: Toshiaki Makita <makita.toshiaki@lab.ntt.co.jp>
Date: Mon, 13 Apr 2015 18:15:10 +0900
Subject: [PATCH] igb: Fix oops on changing number of rings

When changing the number of rings by ethtool -L, q_vectors are reused,
which causes oops because of uninitialized pointers.

- When an rx is reused as a tx, q_vector->rx.ring is not set to NULL, which
  misleads igb_poll() to determine that it has an rx ring although it
  actually points to the tx ring.
- When a tx is reused as an rx, q_vector->rx.ring->skb
  (q_vector->ring[0].skb) has a value that was used as tx_stats before.

Fix these problems by zeroing it out on reuseing it.

Fixes: 02ef6e1d0b00 ("igb: Fix queue allocation method to accommodate changing during runtime")
Signed-off-by: Toshiaki Makita <makita.toshiaki@lab.ntt.co.jp>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
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