netdev - Re: [PATCH] Fix up truesize after pskb_expand

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Message-Id: <1231162275.3334.20.camel@johannes>
Date:	Mon, 05 Jan 2009 14:31:15 +0100
From:	Johannes Berg <johannes@...solutions.net>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
	linville@...driver.com, davem <davem@...emloft.net>
Subject: Re: [PATCH] Fix up truesize after pskb_expand_head() in wireless
	stack

On Mon, 2009-01-05 at 14:36 +0100, Andi Kleen wrote:
> On Mon, Jan 05, 2009 at 02:16:19PM +0100, Johannes Berg wrote:
> > > I didn't use any monitoring with this. No tcpdump, no wireless
> > > sniffer tools or anything. It happened all the time during
> > > normal operation.
> > 
> > You did have a monitor interface up though, didn't you? If nothing
> 
> wmaster0 was up. Is that a monitoring interface? 

No. Only if you do iwconfig ... mode monitor or use iw to create one or
something like that.

I was under the impression that you only modified monitor mode code, but
upon closer inspection (really, you should diff with -p, makes it a lot
easier to review) it seems that you also touched packet defragmentation
code. Are you running a low fragmentation threshold on your network?

Can you
check /sys/kernel/debug/ieee80211/phy*/statistics/rx_expand_skb_head*
please?

> > actually used those skbs then it's likely that the warning didn't result
> > in any corruption at all.
> 
> Nothing was corrupted ever to my knowledge, just lots of spam in my kernel logs.

You wouldn't easily notice any socket memory charge corruption anyway.

johannes

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