netdev - Re: [STABLE 2.6.32 PATCH] net: release dst entry while cache-hot for GSO case too

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Message-ID: <4CB32FDB.4090001@msgid.tls.msk.ru>
Date:	Mon, 11 Oct 2010 19:40:11 +0400
From:	Michael Tokarev <mjt@....msk.ru>
To:	Andrey Vagin <avagin@...nvz.org>
CC:	stable@...nel.org, netdev@...r.kernel.org,
	Krishna Kumar <krkumar2@...ibm.com>,
	"David S. Miller" <davem@...emloft.net>
Subject: Re: [STABLE 2.6.32 PATCH] net: release dst entry while cache-hot
 for GSO case too

Andrey Vagin wrote:
> From: Krishna Kumar <krkumar2@...ibm.com>
> 
> commit 068a2de57ddf4f472e32e7af868613c574ad1d88 upstream.
> 
> Non-GSO code drops dst entry for performance reasons, but
> the same is missing for GSO code. Drop dst while cache-hot
> for GSO case too.
> 
> Note: Without this patch the kernel may oops if used bridged veth
> devices. A bridge set skb->dst = fake_dst_ops, veth transfers this skb
> to netif_receive_skb...ip_rcv_finish and it calls dst_input(skb), but
> fake_dst_ops->input = NULL -> Oops

Hmm.  Isn't this the reason for my mysterious OOPSes (jump to
NULL) which I concluded are due to stack overflow?  See f.e.
http://www.spinics.net/lists/netdev/msg142104.html

This started happening when I updated virtio drivers in a windows
virtual machne to the ones which supports GSO, and my config
involves bridging veth devices, and this is where the prob
actually occurs - when doing guest => virtio => tap => bridge => veth
route....

Thanks!

/mjt
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