[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/sundance.c b/drivers/net/sundance.c
index 08cb7177a175..d500a5771dbc 100644
--- a/drivers/net/sundance.c
+++ b/drivers/net/sundance.c
@@ -1028,7 +1028,7 @@ static void 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. */
                 np->rx_ring[i].frag[0].addr = cpu_to_le32(
-                        pci_map_single(np->pci_dev, skb->tail, np->rx_buf_sz,
+                        pci_map_single(np->pci_dev, skb->data, np->rx_buf_sz,
                                 PCI_DMA_FROMDEVICE));
                 np->rx_ring[i].frag[0].length = cpu_to_le32(np->rx_buf_sz | LastFrag);
         }
@@ -1341,7 +1341,7 @@ static void rx_poll(unsigned long data)
                                                             np->rx_buf_sz,
                                                             PCI_DMA_FROMDEVICE);
 
-                                eth_copy_and_sum(skb, np->rx_skbuff[entry]->tail, pkt_len, 0);
+                                eth_copy_and_sum(skb, np->rx_skbuff[entry]->data, pkt_len, 0);
                                 pci_dma_sync_single_for_device(np->pci_dev,
                                                                desc->frag[0].addr,
                                                                np->rx_buf_sz,
@@ -1400,7 +1400,7 @@ static void refill_rx (struct net_device *dev)
                         skb->dev = dev;         /* Mark as being used by this device. */
                         skb_reserve(skb, 2);    /* Align IP on 16 byte boundaries */
                         np->rx_ring[entry].frag[0].addr = cpu_to_le32(
-                                pci_map_single(np->pci_dev, skb->tail,
+                                pci_map_single(np->pci_dev, skb->data,
                                         np->rx_buf_sz, PCI_DMA_FROMDEVICE));
                 }
                 /* Perhaps we need not reset this field. */