[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/drivers/usb/net/asix.c b/drivers/usb/net/asix.c
index 5808ea082459..f56e2dab3712 100644
--- a/drivers/usb/net/asix.c
+++ b/drivers/usb/net/asix.c
@@ -298,7 +298,7 @@ static int asix_rx_fixup(struct usbnet *dev, struct sk_buff *skb)
                 if (ax_skb) {
                         ax_skb->len = size;
                         ax_skb->data = packet;
-                        ax_skb->tail = packet + size;
+                        skb_set_tail_pointer(ax_skb, size);
                         usbnet_skb_return(dev, ax_skb);
                 } else {
                         return 0;
@@ -338,7 +338,7 @@ static struct sk_buff *asix_tx_fixup(struct usbnet *dev, struct sk_buff *skb,
             && ((headroom + tailroom) >= (4 + padlen))) {
                 if ((headroom < 4) || (tailroom < padlen)) {
                         skb->data = memmove(skb->head + 4, skb->data, skb->len);
-                        skb->tail = skb->data + skb->len;
+                        skb_set_tail_pointer(skb, skb->len);
                 }
         } else {
                 struct sk_buff *skb2;
@@ -356,7 +356,7 @@ static struct sk_buff *asix_tx_fixup(struct usbnet *dev, struct sk_buff *skb,
 
         if ((skb->len % 512) == 0) {
                 cpu_to_le32s(&padbytes);
-                memcpy( skb->tail, &padbytes, sizeof(padbytes));
+                memcpy(skb_tail_pointer(skb), &padbytes, sizeof(padbytes));
                 skb_put(skb, sizeof(padbytes));
         }
         return skb;