[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, 1 insertions, 1 deletions

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 29c53fbb2204..c22cdcd84320 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -733,7 +733,7 @@ static void __pskb_trim_head(struct sk_buff *skb, int len)
         }
         skb_shinfo(skb)->nr_frags = k;
 
-        skb->tail = skb->data;
+        skb_reset_tail_pointer(skb);
         skb->data_len -= len;
         skb->len = skb->data_len;
 }