[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, 2 deletions

diff --git a/drivers/infiniband/hw/amso1100/c2.c b/drivers/infiniband/hw/amso1100/c2.c
index 7698feafa6a7..58bc272bd407 100644
--- a/drivers/infiniband/hw/amso1100/c2.c
+++ b/drivers/infiniband/hw/amso1100/c2.c
@@ -439,7 +439,8 @@ static void c2_rx_error(struct c2_port *c2_port, struct c2_element *elem)
         }
 
         /* Setup the skb for reuse since we're dropping this pkt */
-        elem->skb->tail = elem->skb->data = elem->skb->head;
+        elem->skb->data = elem->skb->head;
+        skb_reset_tail_pointer(elem->skb);
 
         /* Zero out the rxp hdr in the sk_buff */
         memset(elem->skb->data, 0, sizeof(*rxp_hdr));
@@ -521,7 +522,7 @@ static void c2_rx_interrupt(struct net_device *netdev)
                  * "sizeof(struct c2_rxp_hdr)".
                  */
                 skb->data += sizeof(*rxp_hdr);
-                skb->tail = skb->data + buflen;
+                skb_set_tail_pointer(skb, buflen);
                 skb->len = buflen;
                 skb->protocol = eth_type_trans(skb, netdev);