[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, 2 insertions, 2 deletions

diff --git a/net/sctp/sm_make_chunk.c b/net/sctp/sm_make_chunk.c
index 60c5b59d4c65..759ea3d19976 100644
--- a/net/sctp/sm_make_chunk.c
+++ b/net/sctp/sm_make_chunk.c
@@ -1143,7 +1143,7 @@ void *sctp_addto_chunk(struct sctp_chunk *chunk, int len, const void *data)
 
         /* Adjust the chunk length field.  */
         chunk->chunk_hdr->length = htons(chunklen + padlen + len);
-        chunk->chunk_end = chunk->skb->tail;
+        chunk->chunk_end = skb_tail_pointer(chunk->skb);
 
         return target;
 }
@@ -1168,7 +1168,7 @@ int sctp_user_addto_chunk(struct sctp_chunk *chunk, int off, int len,
         /* Adjust the chunk length field.  */
         chunk->chunk_hdr->length =
                 htons(ntohs(chunk->chunk_hdr->length) + len);
-        chunk->chunk_end = chunk->skb->tail;
+        chunk->chunk_end = skb_tail_pointer(chunk->skb);
 
 out:
         return err;