Re: xfs: possible deadlock warning

From: Gu Zheng
Date: Wed May 28 2014 - 23:45:09 EST


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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