[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, 4 insertions, 2 deletions

diff --git a/net/decnet/dn_nsp_out.c b/net/decnet/dn_nsp_out.c
index 84b8c5b45fef..7404653880b0 100644
--- a/net/decnet/dn_nsp_out.c
+++ b/net/decnet/dn_nsp_out.c
@@ -681,8 +681,10 @@ void dn_nsp_send_conninit(struct sock *sk, unsigned char msgflg)
         if (scp->peer.sdn_objnum)
                 type = 0;
 
-        skb_put(skb, dn_sockaddr2username(&scp->peer, skb->tail, type));
-        skb_put(skb, dn_sockaddr2username(&scp->addr, skb->tail, 2));
+        skb_put(skb, dn_sockaddr2username(&scp->peer,
+                                          skb_tail_pointer(skb), type));
+        skb_put(skb, dn_sockaddr2username(&scp->addr,
+                                          skb_tail_pointer(skb), 2));
 
         menuver = DN_MENUVER_ACC | DN_MENUVER_USR;
         if (scp->peer.sdn_flags & SDF_PROXY)