xfs: possible deadlock warning

[Gu Zheng]

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.