From: Eric Dumazet <eric.dumazet@gmail.com>
Date: Tue, 10 Apr 2012 20:08:39 +0000 (+0000)
Subject: net: allow pskb_expand_head() to get maximum tailroom
X-Git-Tag: v3.2.17~95
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=34b0788a13e9c65440e3d736a91f75964356ad67;p=pandora-kernel.git

net: allow pskb_expand_head() to get maximum tailroom

[ Upstream commit 87151b8689d890dfb495081f7be9b9e257f7a2df ]

Marc Merlin reported many order-1 allocations failures in TX path on its
wireless setup, that dont make any sense with MTU=1500 network, and non
SG capable hardware.

Turns out part of the problem comes from pskb_expand_head() not using
ksize() to get exact head size given by kmalloc(). Doing the same thing
than __alloc_skb() allows more tailroom in skb and can prevent future
reallocations.

As a bonus, struct skb_shared_info becomes cache line aligned.

Reported-by: Marc MERLIN <marc@merlins.org>
Tested-by: Marc MERLIN <marc@merlins.org>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
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