[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, 10 insertions, 7 deletions

diff --git a/net/sched/ematch.c b/net/sched/ematch.c
index 959c306c5714..63146d339d81 100644
--- a/net/sched/ematch.c
+++ b/net/sched/ematch.c
@@ -418,17 +418,19 @@ void tcf_em_tree_destroy(struct tcf_proto *tp, struct tcf_ematch_tree *tree)
 int tcf_em_tree_dump(struct sk_buff *skb, struct tcf_ematch_tree *tree, int tlv)
 {
         int i;
-        struct rtattr * top_start = (struct rtattr*) skb->tail;
-        struct rtattr * list_start;
+        u8 *tail;
+        struct rtattr *top_start = (struct rtattr *)skb_tail_pointer(skb);
+        struct rtattr *list_start;
 
         RTA_PUT(skb, tlv, 0, NULL);
         RTA_PUT(skb, TCA_EMATCH_TREE_HDR, sizeof(tree->hdr), &tree->hdr);
 
-        list_start = (struct rtattr *) skb->tail;
+        list_start = (struct rtattr *)skb_tail_pointer(skb);
         RTA_PUT(skb, TCA_EMATCH_TREE_LIST, 0, NULL);
 
+        tail = skb_tail_pointer(skb);
         for (i = 0; i < tree->hdr.nmatches; i++) {
-                struct rtattr *match_start = (struct rtattr*) skb->tail;
+                struct rtattr *match_start = (struct rtattr *)tail;
                 struct tcf_ematch *em = tcf_em_get_match(tree, i);
                 struct tcf_ematch_hdr em_hdr = {
                         .kind = em->ops ? em->ops->kind : TCF_EM_CONTAINER,
@@ -447,11 +449,12 @@ int tcf_em_tree_dump(struct sk_buff *skb, struct tcf_ematch_tree *tree, int tlv)
                 } else if (em->datalen > 0)
                         RTA_PUT_NOHDR(skb, em->datalen, (void *) em->data);
 
-                match_start->rta_len = skb->tail - (u8*) match_start;
+                tail = skb_tail_pointer(skb);
+                match_start->rta_len = tail - (u8 *)match_start;
         }
 
-        list_start->rta_len = skb->tail - (u8 *) list_start;
-        top_start->rta_len = skb->tail - (u8 *) top_start;
+        list_start->rta_len = tail - (u8 *)list_start;
+        top_start->rta_len = tail - (u8 *)top_start;
 
         return 0;