[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, 3 insertions, 3 deletions

diff --git a/include/linux/rtnetlink.h b/include/linux/rtnetlink.h
index 4a629ea70cc4..3a4cb242ecd2 100644
--- a/include/linux/rtnetlink.h
+++ b/include/linux/rtnetlink.h
@@ -605,7 +605,7 @@ extern void __rta_fill(struct sk_buff *skb, int attrtype, int attrlen, const voi
 
 #define RTA_PUT_NOHDR(skb, attrlen, data) \
 ({      RTA_APPEND(skb, RTA_ALIGN(attrlen), data); \
-        memset(skb->tail - (RTA_ALIGN(attrlen) - attrlen), 0, \
+        memset(skb_tail_pointer(skb) - (RTA_ALIGN(attrlen) - attrlen), 0, \
                RTA_ALIGN(attrlen) - attrlen); })
 
 #define RTA_PUT_U8(skb, attrtype, value) \
@@ -637,12 +637,12 @@ extern void __rta_fill(struct sk_buff *skb, int attrtype, int attrlen, const voi
         RTA_PUT(skb, attrtype, 0, NULL);
 
 #define RTA_NEST(skb, type) \
-({      struct rtattr *__start = (struct rtattr *) (skb)->tail; \
+({      struct rtattr *__start = (struct rtattr *)skb_tail_pointer(skb); \
         RTA_PUT(skb, type, 0, NULL); \
         __start;  })
 
 #define RTA_NEST_END(skb, start) \
-({      (start)->rta_len = ((skb)->tail - (unsigned char *) (start)); \
+({      (start)->rta_len = skb_tail_pointer(skb) - (unsigned char *)(start); \
         (skb)->len; })
 
 #define RTA_NEST_CANCEL(skb, start) \