[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/pcnet32.c b/drivers/net/pcnet32.c
index 3213f3e50487..113b68099216 100644
--- a/drivers/net/pcnet32.c
+++ b/drivers/net/pcnet32.c
@@ -1602,7 +1602,7 @@ pcnet32_init_ring(struct net_device *dev)
 
         rmb();
         if (lp->rx_dma_addr[i] == 0)
-            lp->rx_dma_addr[i] = pci_map_single(lp->pci_dev, rx_skbuff->tail,
+            lp->rx_dma_addr[i] = pci_map_single(lp->pci_dev, rx_skbuff->data,
                     PKT_BUF_SZ-2, PCI_DMA_FROMDEVICE);
         lp->rx_ring[i].base = (u32)le32_to_cpu(lp->rx_dma_addr[i]);
         lp->rx_ring[i].buf_length = le16_to_cpu(2-PKT_BUF_SZ);
@@ -1983,7 +1983,7 @@ pcnet32_rx(struct net_device *dev)
                         lp->rx_skbuff[entry] = newskb;
                         newskb->dev = dev;
                         lp->rx_dma_addr[entry] =
-                            pci_map_single(lp->pci_dev, newskb->tail,
+                            pci_map_single(lp->pci_dev, newskb->data,
                                     PKT_BUF_SZ-2, PCI_DMA_FROMDEVICE);
                         lp->rx_ring[entry].base = le32_to_cpu(lp->rx_dma_addr[entry]);
                         rx_in_place = 1;
@@ -2020,7 +2020,7 @@ pcnet32_rx(struct net_device *dev)
                                                 PKT_BUF_SZ-2,
                                                 PCI_DMA_FROMDEVICE);
                     eth_copy_and_sum(skb,
-                            (unsigned char *)(lp->rx_skbuff[entry]->tail),
+                            (unsigned char *)(lp->rx_skbuff[entry]->data),
                             pkt_len,0);
                     pci_dma_sync_single_for_device(lp->pci_dev,
                                                    lp->rx_dma_addr[entry],