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Re: xfs: possible deadlock warning

To: Dave Chinner <david@xxxxxxxxxxxxx>
Subject: Re: xfs: possible deadlock warning
From: Gu Zheng <guz.fnst@xxxxxxxxxxxxxx>
Date: Thu, 29 May 2014 11:34:21 +0800
Cc: <xfs@xxxxxxxxxxx>, linux-kernel <linux-kernel@xxxxxxxxxxxxxxx>
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <20140528060050.GK8554@dastard>
References: <538571D4.70904@xxxxxxxxxxxxxx> <20140528060050.GK8554@dastard>
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:7.0.1) Gecko/20110930 Thunderbird/7.0.1
Hi Dave,

On 05/28/2014 02:00 PM, Dave Chinner wrote:

> On Wed, May 28, 2014 at 01:19:16PM +0800, Gu Zheng wrote:
>> Hi all,
>> When running the latest Linus' tree, the following possible deadlock warning 
>> occurs.
> 
> false positive. There isn't a deadlock between inode locks on
> different filesystems. i.e. there is no dependency between shmem
> inodes and xfs inodes, nor on their security contexts.  Nor can you
> take a page fault on a directory inode, which is the XFS inode lock
> class it's complaining about.

If it's really a noisy, can we avoid this?
 
Thanks,
Gu

> 
> Fundamentally, the problem here is shmem instantiating a new inode
> with the mmap_sem held. That's just plain wrong...

Agree, it's better to prepare the file before going into the protection region. 

> 
> 
> Cheers,
> 
> Dave.


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