[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/net/ipv4/igmp.c b/net/ipv4/igmp.c
index 1fc637fb6750..2506021c2935 100644
--- a/net/ipv4/igmp.c
+++ b/net/ipv4/igmp.c
@@ -348,8 +348,8 @@ static int igmpv3_sendpack(struct sk_buff *skb)
 {
         struct iphdr *pip = ip_hdr(skb);
         struct igmphdr *pig = igmp_hdr(skb);
-        const int iplen = skb->tail - skb_network_header(skb);
-        const int igmplen = skb->tail - skb_transport_header(skb);
+        const int iplen = skb->tail - skb->network_header;
+        const int igmplen = skb->tail - skb->transport_header;
 
         pip->tot_len = htons(iplen);
         ip_send_check(pip);