[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>
diff --git a/drivers/net/e1000/e1000_main.c b/drivers/net/e1000/e1000_main.c
index e86deb2..e7c93f4 100644
--- a/drivers/net/e1000/e1000_main.c
+++ b/drivers/net/e1000/e1000_main.c
@@ -3304,7 +3304,7 @@
* 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 @@
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],