[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>
diff --git a/drivers/usb/atm/usbatm.c b/drivers/usb/atm/usbatm.c
index ec63b0e..4d8f282 100644
--- a/drivers/usb/atm/usbatm.c
+++ b/drivers/usb/atm/usbatm.c
@@ -335,15 +335,15 @@
sarb = instance->cached_vcc->sarb;
- if (sarb->tail + ATM_CELL_PAYLOAD > sarb->end) {
+ if (skb_tail_pointer(sarb) + ATM_CELL_PAYLOAD > sarb->end) {
atm_rldbg(instance, "%s: buffer overrun (sarb->len %u, vcc: 0x%p)!\n",
__func__, sarb->len, vcc);
/* discard cells already received */
skb_trim(sarb, 0);
- UDSL_ASSERT(sarb->tail + ATM_CELL_PAYLOAD <= sarb->end);
+ UDSL_ASSERT(skb_tail_pointer(sarb) + ATM_CELL_PAYLOAD <= sarb->end);
}
- memcpy(sarb->tail, source + ATM_CELL_HEADER, ATM_CELL_PAYLOAD);
+ memcpy(skb_tail_pointer(sarb), source + ATM_CELL_HEADER, ATM_CELL_PAYLOAD);
__skb_put(sarb, ATM_CELL_PAYLOAD);
if (pti & 1) {
@@ -370,7 +370,7 @@
goto out;
}
- if (crc32_be(~0, sarb->tail - pdu_length, pdu_length) != 0xc704dd7b) {
+ if (crc32_be(~0, skb_tail_pointer(sarb) - pdu_length, pdu_length) != 0xc704dd7b) {
atm_rldbg(instance, "%s: packet failed crc check (vcc: 0x%p)!\n",
__func__, vcc);
atomic_inc(&vcc->stats->rx_err);
@@ -396,7 +396,7 @@
goto out; /* atm_charge increments rx_drop */
}
- memcpy(skb->data, sarb->tail - pdu_length, length);
+ memcpy(skb->data, skb_tail_pointer(sarb) - pdu_length, length);
__skb_put(skb, length);
vdbg("%s: sending skb 0x%p, skb->len %u, skb->truesize %u",