igb: fix unmap length bug

driver was mixing NET_IP_ALIGN count bytes in map/unmap calls
unevenly. Only map the bytes that the hardware might dma into

also fix unmap related bug where ->dma was not being cleared
after unmap
Signed-off-by: NJesse Brandeburg <jesse.brandeburg@intel.com>
Signed-off-by: NJeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/igb/igb_main.c

@@ -4549,11 +4549,12 @@ static bool igb_clean_rx_irq_adv(struct igb_ring *rx_ring,
 		cleaned = true;
 		cleaned_count++;
 
+		/* this is the fast path for the non-packet split case */
 		if (!adapter->rx_ps_hdr_size) {
 			pci_unmap_single(pdev, buffer_info->dma,
-					 adapter->rx_buffer_len +
-					   NET_IP_ALIGN,
+					 adapter->rx_buffer_len,
 					 PCI_DMA_FROMDEVICE);
+			buffer_info->dma = 0;
 			skb_put(skb, length);
 			goto send_up;
 		}
@@ -4570,8 +4571,9 @@ static bool igb_clean_rx_irq_adv(struct igb_ring *rx_ring,
 
 		if (!skb_shinfo(skb)->nr_frags) {
 			pci_unmap_single(pdev, buffer_info->dma,
-					 adapter->rx_ps_hdr_size + NET_IP_ALIGN,
+					 adapter->rx_ps_hdr_size,
 					 PCI_DMA_FROMDEVICE);
+			buffer_info->dma = 0;
 			skb_put(skb, hlen);
 		}
 
@@ -4713,7 +4715,6 @@ static void igb_alloc_rx_buffers_adv(struct igb_ring *rx_ring,
 		bufsz = adapter->rx_ps_hdr_size;
 	else
 		bufsz = adapter->rx_buffer_len;
-	bufsz += NET_IP_ALIGN;
 
 	while (cleaned_count--) {
 		rx_desc = E1000_RX_DESC_ADV(*rx_ring, i);
@@ -4737,7 +4738,7 @@ static void igb_alloc_rx_buffers_adv(struct igb_ring *rx_ring,
 		}
 
 		if (!buffer_info->skb) {
-			skb = netdev_alloc_skb(netdev, bufsz);
+			skb = netdev_alloc_skb(netdev, bufsz + NET_IP_ALIGN);
 			if (!skb) {
 				adapter->alloc_rx_buff_failed++;
 				goto no_buffers;