From: David S. Miller <davem@davemloft.net>
Date: Tue, 5 Jul 2005 22:17:25 +0000 (-0700)
Subject: [TCP]: Simplify SKB data portion allocation with NETIF_F_SG.
X-Git-Tag: v2.6.13-rc2~6^2~18
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=c65f7f00c587828e3d50737805a78f74804972de;p=pandora-kernel.git

[TCP]: Simplify SKB data portion allocation with NETIF_F_SG.

The ideal and most optimal layout for an SKB when doing
scatter-gather is to put all the headers at skb->data, and
all the user data in the page array.

This makes SKB splitting and combining extremely simple,
especially before a packet goes onto the wire the first
time.

So, when sk_stream_alloc_pskb() is given a zero size, make
sure there is no skb_tailroom().  This is achieved by applying
SKB_DATA_ALIGN() to the header length used here.

Next, make select_size() in TCP output segmentation use a
length of zero when NETIF_F_SG is true on the outgoing
interface.

Signed-off-by: David S. Miller <davem@davemloft.net>
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