This is a note to let you know that I've just added the patch titled
skb: avoid unnecessary reallocations in __skb_cow
to the 3.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
skb-avoid-unnecessary-reallocations-in-__skb_cow.patch
and it can be found in the queue-3.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.
>From 64305df8b10a0ea32cbef6a880c0b8911cca6cb8 Mon Sep 17 00:00:00 2001
From: Felix Fietkau <n...@openwrt.org>
Date: Tue, 29 May 2012 03:35:08 +0000
Subject: skb: avoid unnecessary reallocations in __skb_cow
From: Felix Fietkau <n...@openwrt.org>
[ Upstream commit 617c8c11236716dcbda877e764b7bf37c6fd8063 ]
At the beginning of __skb_cow, headroom gets set to a minimum of
NET_SKB_PAD. This causes unnecessary reallocations if the buffer was not
cloned and the headroom is just below NET_SKB_PAD, but still more than the
amount requested by the caller.
This was showing up frequently in my tests on VLAN tx, where
vlan_insert_tag calls skb_cow_head(skb, VLAN_HLEN).
Locally generated packets should have enough headroom, and for forward
paths, we already have NET_SKB_PAD bytes of headroom, so we don't need to
add any extra space here.
Signed-off-by: Felix Fietkau <n...@openwrt.org>
Signed-off-by: Eric Dumazet <eduma...@google.com>
Signed-off-by: David S. Miller <da...@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
include/linux/skbuff.h | 2 --
1 file changed, 2 deletions(-)
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -1881,8 +1881,6 @@ static inline int __skb_cow(struct sk_bu
{
int delta = 0;
- if (headroom < NET_SKB_PAD)
- headroom = NET_SKB_PAD;
if (headroom > skb_headroom(skb))
delta = headroom - skb_headroom(skb);
Patches currently in stable-queue which might be from n...@openwrt.org are
queue-3.4/ath9k-fix-a-use-after-free-bug-when-ath_tx_setup_buffer-fails.patch
queue-3.4/skb-avoid-unnecessary-reallocations-in-__skb_cow.patch
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