[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>

3 files changed, 7 insertions, 9 deletions

diff --git a/include/net/inet_ecn.h b/include/net/inet_ecn.h
index 06a2c69a89e5..de8399a79774 100644
--- a/include/net/inet_ecn.h
+++ b/include/net/inet_ecn.h
@@ -114,14 +114,12 @@ static inline int INET_ECN_set_ce(struct sk_buff *skb)
 {
         switch (skb->protocol) {
         case __constant_htons(ETH_P_IP):
-                if (skb_network_header(skb) + sizeof(struct iphdr) <=
-                    skb->tail)
+                if (skb->network_header + sizeof(struct iphdr) <= skb->tail)
                         return IP_ECN_set_ce(ip_hdr(skb));
                 break;
 
         case __constant_htons(ETH_P_IPV6):
-                if (skb_network_header(skb) + sizeof(struct ipv6hdr) <=
-                    skb->tail)
+                if (skb->network_header + sizeof(struct ipv6hdr) <= skb->tail)
                         return IP6_ECN_set_ce(ipv6_hdr(skb));
                 break;
         }
diff --git a/include/net/netlink.h b/include/net/netlink.h
index bcaf67b7a19d..2c7ab107f20d 100644
--- a/include/net/netlink.h
+++ b/include/net/netlink.h
@@ -525,7 +525,7 @@ static inline struct sk_buff *nlmsg_new(size_t payload, gfp_t flags)
  */
 static inline int nlmsg_end(struct sk_buff *skb, struct nlmsghdr *nlh)
 {
-        nlh->nlmsg_len = skb->tail - (unsigned char *) nlh;
+        nlh->nlmsg_len = skb_tail_pointer(skb) - (unsigned char *)nlh;
 
         return skb->len;
 }
@@ -538,7 +538,7 @@ static inline int nlmsg_end(struct sk_buff *skb, struct nlmsghdr *nlh)
  */
 static inline void *nlmsg_get_pos(struct sk_buff *skb)
 {
-        return skb->tail;
+        return skb_tail_pointer(skb);
 }
 
 /**
@@ -940,7 +940,7 @@ static inline unsigned long nla_get_msecs(struct nlattr *nla)
  */
 static inline struct nlattr *nla_nest_start(struct sk_buff *skb, int attrtype)
 {
-        struct nlattr *start = (struct nlattr *) skb->tail;
+        struct nlattr *start = (struct nlattr *)skb_tail_pointer(skb);
 
         if (nla_put(skb, attrtype, 0, NULL) < 0)
                 return NULL;
@@ -960,7 +960,7 @@ static inline struct nlattr *nla_nest_start(struct sk_buff *skb, int attrtype)
  */
 static inline int nla_nest_end(struct sk_buff *skb, struct nlattr *start)
 {
-        start->nla_len = skb->tail - (unsigned char *) start;
+        start->nla_len = skb_tail_pointer(skb) - (unsigned char *)start;
         return skb->len;
 }
 
diff --git a/include/net/pkt_cls.h b/include/net/pkt_cls.h
index dcb3a91f1364..4129df708079 100644
--- a/include/net/pkt_cls.h
+++ b/include/net/pkt_cls.h
@@ -337,7 +337,7 @@ static inline unsigned char * tcf_get_base_ptr(struct sk_buff *skb, int layer)
 static inline int tcf_valid_offset(const struct sk_buff *skb,
                                    const unsigned char *ptr, const int len)
 {
-        return unlikely((ptr + len) < skb->tail && ptr > skb->head);
+        return unlikely((ptr + len) < skb_tail_pointer(skb) && ptr > skb->head);
 }
 
 #ifdef CONFIG_NET_CLS_IND