[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 84b8c5b..7404653 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 bb73bf1..9678b09 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 780a141f..544c455 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 0e62def..ceefd9d 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;