linux-kernel - Re: 3.7.10+: BUG Dentry still in use [unmount of cifs cifs]

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Date:	Thu, 07 Mar 2013 14:18:13 -0800
From:	Ben Greear <greearb@...delatech.com>
To:	Mateusz Guzik <mguzik@...hat.com>
CC:	linux-cifs@...r.kernel.org,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Jeff Layton <jlayton@...hat.com>
Subject: Re: 3.7.10+:  BUG Dentry still in use [unmount of cifs cifs]

On 03/07/2013 11:19 AM, Mateusz Guzik wrote:
> On Tue, Mar 05, 2013 at 10:54:56AM -0800, Ben Greear wrote:
>> In doing some CIFS testing (utilizing it's feature to bind to local
>> address..but not sure that matters), we saw this error when trying
>> to un-mount.
>>
>> Our kernel is patched (nfs, some networking related patches), but there
>> are no out-of-kernel patches to CIFS, so I don't *think* this is anything
>> we could have caused.
>>
>> This problem appears to be easily reproducible, so we will be happy
>> to test patches if anyone has any suggestions.
>>
>> BUG: Dentry ffff8800c07e43c0{i=45762,n=cifs2-01.7.lf-data} still in use (1) [unmount of cifs cifs]
>
> We encountered similar panic, but it was related to writes. In our case
> the problem was that some cifsInodeInfo holding dentry references were
> still around (in slow-work queue) during superblock destruction in unmount.
>
> I reproduced the problem on 3.8 kernel (sorry, no 3.7 handy) with reads
> as well, which should match your scenario.
>
> I attached a patch that deals with this problem by grabbing refcounts to
> cifs superblock on cifsInodeInfo creation. This delays sb destruction
> until all cifsInodeInfos are gone. I didn't test it on 3.7.10 kernel but
> it should work fine.

The 3.7.10 patch applied cleanly and appears to fix our problem.

Thanks so much for the patch!

Ben

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

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