[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/ns83820.c b/drivers/net/ns83820.c
index cc7965271778..e64df4d0800b 100644
--- a/drivers/net/ns83820.c
+++ b/drivers/net/ns83820.c
@@ -574,7 +574,7 @@ static inline int ns83820_add_rx_skb(struct ns83820 *dev, struct sk_buff *skb)
 
 	dev->rx_info.next_empty = (next_empty + 1) % NR_RX_DESC;
 	cmdsts = REAL_RX_BUF_SIZE | CMDSTS_INTR;
-	buf = pci_map_single(dev->pci_dev, skb->tail,
+	buf = pci_map_single(dev->pci_dev, skb->data,
 			     REAL_RX_BUF_SIZE, PCI_DMA_FROMDEVICE);
 	build_rx_desc(dev, sg, 0, buf, cmdsts, 0);
 	/* update link of previous rx */
@@ -604,7 +604,7 @@ static inline int rx_refill(struct net_device *ndev, int gfp)
 		if (unlikely(!skb))
 			break;
 
-		res = (long)skb->tail & 0xf;
+		res = (long)skb->data & 0xf;
 		res = 0x10 - res;
 		res &= 0xf;
 		skb_reserve(skb, res);