[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, 5 insertions, 4 deletions

diff --git a/net/ipv4/ipmr.c b/net/ipv4/ipmr.c
index 50d0b301380e..ea0a491dce92 100644
--- a/net/ipv4/ipmr.c
+++ b/net/ipv4/ipmr.c
@@ -513,7 +513,8 @@ static void ipmr_cache_resolve(struct mfc_cache *uc, struct mfc_cache *c)
                         struct nlmsghdr *nlh = (struct nlmsghdr *)skb_pull(skb, sizeof(struct iphdr));
 
                         if (ipmr_fill_mroute(skb, c, NLMSG_DATA(nlh)) > 0) {
-                                nlh->nlmsg_len = skb->tail - (u8*)nlh;
+                                nlh->nlmsg_len = (skb_tail_pointer(skb) -
+                                                  (u8 *)nlh);
                         } else {
                                 nlh->nlmsg_type = NLMSG_ERROR;
                                 nlh->nlmsg_len = NLMSG_LENGTH(sizeof(struct nlmsgerr));
@@ -580,7 +581,7 @@ static int ipmr_cache_report(struct sk_buff *pkt, vifi_t vifi, int assert)
          *      Copy the IP header
          */
 
-        skb_set_network_header(skb, skb->tail - skb->data);
+        skb->network_header = skb->tail;
         skb_put(skb, ihl);
         memcpy(skb->data,pkt->data,ihl);
         ip_hdr(skb)->protocol = 0;                      /* Flag to the kernel this is a route add */
@@ -1544,7 +1545,7 @@ ipmr_fill_mroute(struct sk_buff *skb, struct mfc_cache *c, struct rtmsg *rtm)
         int ct;
         struct rtnexthop *nhp;
         struct net_device *dev = vif_table[c->mfc_parent].dev;
-        u8 *b = skb->tail;
+        u8 *b = skb_tail_pointer(skb);
         struct rtattr *mp_head;
 
         if (dev)
@@ -1564,7 +1565,7 @@ ipmr_fill_mroute(struct sk_buff *skb, struct mfc_cache *c, struct rtmsg *rtm)
                 }
         }
         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;
         rtm->rtm_type = RTN_MULTICAST;
         return 1;