[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>

4 files changed, 11 insertions, 9 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)
diff --git a/net/decnet/dn_route.c b/net/decnet/dn_route.c
index bb73bf16630f..9678b096b844 100644
--- a/net/decnet/dn_route.c
+++ b/net/decnet/dn_route.c
@@ -1468,7 +1468,7 @@ static int dn_rt_fill_info(struct sk_buff *skb, u32 pid, u32 seq,
         struct dn_route *rt = (struct dn_route *)skb->dst;
         struct rtmsg *r;
         struct nlmsghdr *nlh;
-        unsigned char *b = skb->tail;
+        unsigned char *b = skb_tail_pointer(skb);
         long expires;
 
         nlh = NLMSG_NEW(skb, pid, seq, event, sizeof(*r), flags);
@@ -1509,7 +1509,7 @@ static int dn_rt_fill_info(struct sk_buff *skb, u32 pid, u32 seq,
         if (rt->fl.iif)
                 RTA_PUT(skb, RTA_IIF, sizeof(int), &rt->fl.iif);
 
-        nlh->nlmsg_len = skb->tail - b;
+        nlh->nlmsg_len = skb_tail_pointer(skb) - b;
         return skb->len;
 
 nlmsg_failure:
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;
 
 
diff --git a/net/decnet/netfilter/dn_rtmsg.c b/net/decnet/netfilter/dn_rtmsg.c
index 0e62def05a58..ceefd9dd0c92 100644
--- a/net/decnet/netfilter/dn_rtmsg.c
+++ b/net/decnet/netfilter/dn_rtmsg.c
@@ -33,7 +33,7 @@ static struct sk_buff *dnrmg_build_message(struct sk_buff *rt_skb, int *errp)
 {
         struct sk_buff *skb = NULL;
         size_t size;
-        unsigned char *old_tail;
+        sk_buff_data_t old_tail;
         struct nlmsghdr *nlh;
         unsigned char *ptr;
         struct nf_dn_rtmsg *rtm;