[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, 1 deletions

diff --git a/drivers/atm/idt77252.c b/drivers/atm/idt77252.c
index b4b80140c398..1e49799cd6cf 100644
--- a/drivers/atm/idt77252.c
+++ b/drivers/atm/idt77252.c
@@ -1816,7 +1816,8 @@ push_rx_skb(struct idt77252_dev *card, struct sk_buff *skb, int queue)
         u32 handle;
         u32 addr;
 
-        skb->data = skb->tail = skb->head;
+        skb->data = skb->head;
+        skb_reset_tail_pointer(skb);
         skb->len = 0;
 
         skb_reserve(skb, 16);