[NET]: Remove gratuitous use of skb->tail in network drivers.

Many drivers use skb->tail unnecessarily.

In these situations, the code roughly looks like:

	dev = dev_alloc_skb(...);

	[optional] skb_reserve(skb, ...);

	... skb->tail ...

But even if the skb_reserve() happens, skb->data equals
skb->tail.  So it doesn't make any sense to use anything
other than skb->data in these cases.

Another case was the s2io.c driver directly mucking with
the skb->data and skb->tail pointers.  It really just wanted
to do an skb_reserve(), so that's what the code was changed
to do instead.

Another reason I'm making this change as it allows some SKB
cleanups I have planned simpler to merge.  In those cleanups,
skb->head, skb->tail, and skb->end pointers are removed, and
replaced with skb->head_room and skb->tail_room integers.

Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Jeff Garzik <jgarzik@pobox.com>

1 files changed, 3 insertions, 3 deletions

diff --git a/drivers/net/starfire.c b/drivers/net/starfire.c
index 12e2b6826fa3..88b89dc95c77 100644
--- a/drivers/net/starfire.c
+++ b/drivers/net/starfire.c
@@ -1286,7 +1286,7 @@ static void init_ring(struct net_device *dev)
 		np->rx_info[i].skb = skb;
 		if (skb == NULL)
 			break;
-		np->rx_info[i].mapping = pci_map_single(np->pci_dev, skb->tail, np->rx_buf_sz, PCI_DMA_FROMDEVICE);
+		np->rx_info[i].mapping = pci_map_single(np->pci_dev, skb->data, np->rx_buf_sz, PCI_DMA_FROMDEVICE);
 		skb->dev = dev;			/* Mark as being used by this device. */
 		/* Grrr, we cannot offset to correctly align the IP header. */
 		np->rx_ring[i].rxaddr = cpu_to_dma(np->rx_info[i].mapping | RxDescValid);
@@ -1572,7 +1572,7 @@ static int __netdev_rx(struct net_device *dev, int *quota)
 			pci_dma_sync_single_for_cpu(np->pci_dev,
 						    np->rx_info[entry].mapping,
 						    pkt_len, PCI_DMA_FROMDEVICE);
-			eth_copy_and_sum(skb, np->rx_info[entry].skb->tail, pkt_len, 0);
+			eth_copy_and_sum(skb, np->rx_info[entry].skb->data, pkt_len, 0);
 			pci_dma_sync_single_for_device(np->pci_dev,
 						       np->rx_info[entry].mapping,
 						       pkt_len, PCI_DMA_FROMDEVICE);
@@ -1696,7 +1696,7 @@ static void refill_rx_ring(struct net_device *dev)
 			if (skb == NULL)
 				break;	/* Better luck next round. */
 			np->rx_info[entry].mapping =
-				pci_map_single(np->pci_dev, skb->tail, np->rx_buf_sz, PCI_DMA_FROMDEVICE);
+				pci_map_single(np->pci_dev, skb->data, np->rx_buf_sz, PCI_DMA_FROMDEVICE);
 			skb->dev = dev;	/* Mark as being used by this device. */
 			np->rx_ring[entry].rxaddr =
 				cpu_to_dma(np->rx_info[entry].mapping | RxDescValid);