[net 4/6] ixgbe: Fix Tx map failure path

[Jeff Kirsher]

From: Alexander Duyck <alexander.h.du...@intel.com>

This patch is a partial revert of "ixgbe: Don't bother clearing buffer
memory for descriptor rings". Specifically I messed up the exception
handling path a bit and this resulted in us incorrectly adding the count
back in when we didn't need to.

In order to make this simpler I am reverting most of the exception handling
path change and instead just replacing the bit that was handled by the
unmap_and_free call.

Fixes: ffed21bcee7a ("ixgbe: Don't bother clearing buffer memory for descriptor 
rings")
Signed-off-by: Alexander Duyck <alexander.h.du...@intel.com>
Tested-by: Andrew Bowers <andrewx.bow...@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirs...@intel.com>
---
 drivers/net/ethernet/intel/ixgbe/ixgbe_main.c | 18 ++++++------------
 1 file changed, 6 insertions(+), 12 deletions(-)

diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c 
b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
index 4d76afd13868..6d5f31e94358 100644
--- a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
+++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
@@ -8020,29 +8020,23 @@ static int ixgbe_tx_map(struct ixgbe_ring *tx_ring,
        return 0;
 dma_error:
        dev_err(tx_ring->dev, "TX DMA map failed\n");
-       tx_buffer = &tx_ring->tx_buffer_info[i];
 
        /* clear dma mappings for failed tx_buffer_info map */
-       while (tx_buffer != first) {
+       for (;;) {
+               tx_buffer = &tx_ring->tx_buffer_info[i];
                if (dma_unmap_len(tx_buffer, len))
                        dma_unmap_page(tx_ring->dev,
                                       dma_unmap_addr(tx_buffer, dma),
                                       dma_unmap_len(tx_buffer, len),
                                       DMA_TO_DEVICE);
                dma_unmap_len_set(tx_buffer, len, 0);
-
-               if (i--)
+               if (tx_buffer == first)
+                       break;
+               if (i == 0)
                        i += tx_ring->count;
-               tx_buffer = &tx_ring->tx_buffer_info[i];
+               i--;
        }
 
-       if (dma_unmap_len(tx_buffer, len))
-               dma_unmap_single(tx_ring->dev,
-                                dma_unmap_addr(tx_buffer, dma),
-                                dma_unmap_len(tx_buffer, len),
-                                DMA_TO_DEVICE);
-       dma_unmap_len_set(tx_buffer, len, 0);
-
        dev_kfree_skb_any(first->skb);
        first->skb = NULL;
 
-- 
2.14.2