[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, 4 deletions

diff --git a/net/decnet/dn_table.c b/net/decnet/dn_table.c
index 780a141f8342..544c45540746 100644
--- a/net/decnet/dn_table.c
+++ b/net/decnet/dn_table.c
@@ -295,7 +295,7 @@ static int dn_fib_dump_info(struct sk_buff *skb, u32 pid, u32 seq, int event,
 {
         struct rtmsg *rtm;
         struct nlmsghdr *nlh;
-        unsigned char *b = skb->tail;
+        unsigned char *b = skb_tail_pointer(skb);
 
         nlh = NLMSG_NEW(skb, pid, seq, event, sizeof(*rtm), flags);
         rtm = NLMSG_DATA(nlh);
@@ -337,13 +337,13 @@ static int dn_fib_dump_info(struct sk_buff *skb, u32 pid, u32 seq, int event,
                         nhp->rtnh_ifindex = nh->nh_oif;
                         if (nh->nh_gw)
                                 RTA_PUT(skb, RTA_GATEWAY, 2, &nh->nh_gw);
-                        nhp->rtnh_len = skb->tail - (unsigned char *)nhp;
+                        nhp->rtnh_len = skb_tail_pointer(skb) - (unsigned char *)nhp;
                 } endfor_nexthops(fi);
                 mp_head->rta_type = RTA_MULTIPATH;
-                mp_head->rta_len = skb->tail - (u8*)mp_head;
+                mp_head->rta_len = skb_tail_pointer(skb) - (u8 *)mp_head;
         }
 
-        nlh->nlmsg_len = skb->tail - b;
+        nlh->nlmsg_len = skb_tail_pointer(skb) - b;
         return skb->len;