[SK_BUFF]: Convert skb->tail to sk_buff_data_t

So that it is also an offset from skb->head, reduces its size from 8 to 4 bytes
on 64bit architectures, allowing us to combine the 4 bytes hole left by the
layer headers conversion, reducing struct sk_buff size to 256 bytes, i.e. 4
64byte cachelines, and since the sk_buff slab cache is SLAB_HWCACHE_ALIGN...
:-)

Many calculations that previously required that skb->{transport,network,
mac}_header be first converted to a pointer now can be done directly, being
meaningful as offsets or pointers.

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 2 deletions

diff --git a/drivers/net/e1000/e1000_main.c b/drivers/net/e1000/e1000_main.c
index e86deb2ef823..e7c93f44f810 100644
--- a/drivers/net/e1000/e1000_main.c
+++ b/drivers/net/e1000/e1000_main.c
@@ -3304,7 +3304,7 @@ e1000_xmit_frame(struct sk_buff *skb, struct net_device *netdev)
                                  * NOTE: this is a TSO only workaround
                                  * if end byte alignment not correct move us
                                  * into the next dword */
-                                if ((unsigned long)(skb->tail - 1) & 4)
+                                if ((unsigned long)(skb_tail_pointer(skb) - 1) & 4)
                                         break;
                                 /* fall through */
                         case e1000_82571:
@@ -4388,7 +4388,7 @@ e1000_clean_rx_irq_ps(struct e1000_adapter *adapter,
                                 PCI_DMA_FROMDEVICE);
                         vaddr = kmap_atomic(ps_page->ps_page[0],
                                             KM_SKB_DATA_SOFTIRQ);
-                        memcpy(skb->tail, vaddr, l1);
+                        memcpy(skb_tail_pointer(skb), vaddr, l1);
                         kunmap_atomic(vaddr, KM_SKB_DATA_SOFTIRQ);
                         pci_dma_sync_single_for_device(pdev,
                                 ps_page_dma->ps_page_dma[0],