netdev - Re: 3.7.3+: Bad paging request in ip_rcv_finish while running NFS traffic.

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Message-ID: <510028A7.1080902@candelatech.com>
Date:	Wed, 23 Jan 2013 10:15:03 -0800
From:	Ben Greear <greearb@...delatech.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
CC:	netdev <netdev@...r.kernel.org>,
	"linux-nfs@...r.kernel.org" <linux-nfs@...r.kernel.org>
Subject: Re: 3.7.3+:  Bad paging request in ip_rcv_finish while running NFS
 traffic.

On 01/23/2013 05:35 AM, Eric Dumazet wrote:
> On Tue, 2013-01-22 at 23:14 -0800, Ben Greear wrote:
>
>> How are the non-ref-counted dst objects used safely?  Any chance
>> that tearing down the IP protocol on a device (or deleting a device)
>> could delete a dst that is referenced by an skb (and thus crashes as
>> I see)?
>
> There is probably a bug. Normally it should be RCU protected.

I'm building net-next, and will do some testing on it later today
if all goes well.

In the meantime, a few questions about RCU.

If the non-ref-counted dst is protected by RCU, does that mean
that from the time we acquire the pointer (ie, set it in the skb),
to the time we clear the pointer from the skb, we must be under
RCU read lock?

If so, that means that ip_rcv_finish must be called under RCU
read lock, etc?

Btw, this seems non related to NFS, so I'm dropping them
from CC after this email unless I hear a request otherwise.

Thanks,
Ben

-- 
Ben Greear <greearb@...delatech.com>
Candela Technologies Inc  http://www.candelatech.com

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