[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, 2 insertions, 2 deletions

diff --git a/drivers/net/r8169.c b/drivers/net/r8169.c
index ce449fe..d5afe05 100644
--- a/drivers/net/r8169.c
+++ b/drivers/net/r8169.c
@@ -1876,7 +1876,7 @@ static int rtl8169_alloc_rx_skb(struct pci_dev *pdev, struct sk_buff **sk_buff,
 	skb_reserve(skb, NET_IP_ALIGN);
 	*sk_buff = skb;
 
-	mapping = pci_map_single(pdev, skb->tail, rx_buf_sz,
+	mapping = pci_map_single(pdev, skb->data, rx_buf_sz,
 				 PCI_DMA_FROMDEVICE);
 
 	rtl8169_map_to_asic(desc, mapping, rx_buf_sz);
@@ -2336,7 +2336,7 @@ static inline int rtl8169_try_rx_copy(struct sk_buff **sk_buff, int pkt_size,
 		skb = dev_alloc_skb(pkt_size + NET_IP_ALIGN);
 		if (skb) {
 			skb_reserve(skb, NET_IP_ALIGN);
-			eth_copy_and_sum(skb, sk_buff[0]->tail, pkt_size, 0);
+			eth_copy_and_sum(skb, sk_buff[0]->data, pkt_size, 0);
 			*sk_buff = skb;
 			rtl8169_mark_to_asic(desc, rx_buf_sz);
 			ret = 0;