[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/net/ipv6/mcast.c b/net/ipv6/mcast.c
index 4c45bcc..6c27589 100644
--- a/net/ipv6/mcast.c
+++ b/net/ipv6/mcast.c
@@ -1423,7 +1423,7 @@
memcpy(skb_put(skb, sizeof(ra)), ra, sizeof(ra));
- skb_set_transport_header(skb, skb->tail - skb->data);
+ skb_set_transport_header(skb, skb_tail_pointer(skb) - skb->data);
skb_put(skb, sizeof(*pmr));
pmr = (struct mld2_report *)skb_transport_header(skb);
pmr->type = ICMPV6_MLD2_REPORT;
@@ -1468,8 +1468,8 @@
int err;
IP6_INC_STATS(idev, IPSTATS_MIB_OUTREQUESTS);
- payload_len = skb->tail - skb_network_header(skb) - sizeof(*pip6);
- mldlen = skb->tail - skb_transport_header(skb);
+ payload_len = (skb->tail - skb->network_header) - sizeof(*pip6);
+ mldlen = skb->tail - skb->transport_header;
pip6->payload_len = htons(payload_len);
pmr->csum = csum_ipv6_magic(&pip6->saddr, &pip6->daddr, mldlen,