[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, 4 insertions, 4 deletions

diff --git a/drivers/net/eepro100.c b/drivers/net/eepro100.c
index 98b3a2fdce90..1795425f512e 100644
--- a/drivers/net/eepro100.c
+++ b/drivers/net/eepro100.c
@@ -1269,7 +1269,7 @@ speedo_init_rx_ring(struct net_device *dev)
                 if (skb == NULL)
                         break;                  /* OK.  Just initially short of Rx bufs. */
                 skb->dev = dev;                 /* Mark as being used by this device. */
-                rxf = (struct RxFD *)skb->tail;
+                rxf = (struct RxFD *)skb->data;
                 sp->rx_ringp[i] = rxf;
                 sp->rx_ring_dma[i] =
                         pci_map_single(sp->pdev, rxf,
@@ -1661,7 +1661,7 @@ static inline struct RxFD *speedo_rx_alloc(struct net_device *dev, int entry)
                 sp->rx_ringp[entry] = NULL;
                 return NULL;
         }
-        rxf = sp->rx_ringp[entry] = (struct RxFD *)skb->tail;
+        rxf = sp->rx_ringp[entry] = (struct RxFD *)skb->data;
         sp->rx_ring_dma[entry] =
                 pci_map_single(sp->pdev, rxf,
                                            PKT_BUF_SZ + sizeof(struct RxFD), PCI_DMA_FROMDEVICE);
@@ -1808,10 +1808,10 @@ speedo_rx(struct net_device *dev)
 
 #if 1 || USE_IP_CSUM
                                 /* Packet is in one chunk -- we can copy + cksum. */
-                                eth_copy_and_sum(skb, sp->rx_skbuff[entry]->tail, pkt_len, 0);
+                                eth_copy_and_sum(skb, sp->rx_skbuff[entry]->data, pkt_len, 0);
                                 skb_put(skb, pkt_len);
 #else
-                                memcpy(skb_put(skb, pkt_len), sp->rx_skbuff[entry]->tail,
+                                memcpy(skb_put(skb, pkt_len), sp->rx_skbuff[entry]->data,
                                            pkt_len);
 #endif
                                 pci_dma_sync_single_for_device(sp->pdev, sp->rx_ring_dma[entry],