[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/epic100.c b/drivers/net/epic100.c
index 81ebaedaa240..87f522738bfc 100644
--- a/drivers/net/epic100.c
+++ b/drivers/net/epic100.c
@@ -1003,7 +1003,7 @@ static void epic_init_ring(struct net_device *dev)
                 skb->dev = dev;                 /* Mark as being used by this device. */
                 skb_reserve(skb, 2);    /* 16 byte align the IP header. */
                 ep->rx_ring[i].bufaddr = pci_map_single(ep->pci_dev, 
-                        skb->tail, ep->rx_buf_sz, PCI_DMA_FROMDEVICE);
+                        skb->data, ep->rx_buf_sz, PCI_DMA_FROMDEVICE);
                 ep->rx_ring[i].rxstatus = cpu_to_le32(DescOwn);
         }
         ep->dirty_rx = (unsigned int)(i - RX_RING_SIZE);
@@ -1274,7 +1274,7 @@ static int epic_rx(struct net_device *dev, int budget)
                                                             ep->rx_ring[entry].bufaddr,
                                                             ep->rx_buf_sz,
                                                             PCI_DMA_FROMDEVICE);
-                                eth_copy_and_sum(skb, ep->rx_skbuff[entry]->tail, pkt_len, 0);
+                                eth_copy_and_sum(skb, ep->rx_skbuff[entry]->data, pkt_len, 0);
                                 skb_put(skb, pkt_len);
                                 pci_dma_sync_single_for_device(ep->pci_dev,
                                                                ep->rx_ring[entry].bufaddr,
@@ -1308,7 +1308,7 @@ static int epic_rx(struct net_device *dev, int budget)
                         skb->dev = dev;                 /* Mark as being used by this device. */
                         skb_reserve(skb, 2);    /* Align IP on 16 byte boundaries */
                         ep->rx_ring[entry].bufaddr = pci_map_single(ep->pci_dev, 
-                                skb->tail, ep->rx_buf_sz, PCI_DMA_FROMDEVICE);
+                                skb->data, ep->rx_buf_sz, PCI_DMA_FROMDEVICE);
                         work_done++;
                 }
                 ep->rx_ring[entry].rxstatus = cpu_to_le32(DescOwn);