netdev - Re: ipv6: tunnel: hang when destroying ipv6 tunnel

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Message-ID: <CA+1xoqd0JJ-Z+hmwgdZkBiu1anEh6iz1jJboULPp-drUzO37Ew@mail.gmail.com>
Date:	Wed, 11 Apr 2012 14:20:40 +0200
From:	Sasha Levin <levinsasha928@...il.com>
To:	Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
Cc:	garlick@...l.gov, ericvh@...il.com, oleg@...hat.com,
	eric.dumazet@...il.com, davem@...emloft.net, kuznet@....inr.ac.ru,
	jmorris@...ei.org, yoshfuji@...ux-ipv6.org, kaber@...sh.net,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	davej@...hat.com
Subject: Re: ipv6: tunnel: hang when destroying ipv6 tunnel

>> Yes but in the unlikely event that this happens, the effect is a small
>> memory leak for the duration of the mount.  On the other hand if the
>> fid is destroyed without successfully informing the server, then
>> subsequent operations that involve new file references will fail
>> when that fid number is reused, and the mount becomes unusable.
>
> I don't know whether Sasha's problem is caused by this patch or not.
> But p9_client_clunk() is called from many functions in fs/9p/ directory.
> They are assuming that p9_client_clunk() will call p9_fid_destroy() but
> this patch is breaking that assumption. I think this is the cause of hang which
> Sasha is experiencing because Sasha's trace shows that call_usermodehelper() is
> blocked by functions in fs/9p/ directory. Seems inconsistency state problem.

I'd be happy to try out any other patches or help debugging this issue.

Which behavior did this patch fix exactly? can I just revert it and
try running without it?
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