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Date: Fri, 25 Sep 2015 12:23:34 -0600
From: Ross Zwisler <ross.zwisler@linux.intel.com>
To: Dave Chinner <david@fromorbit.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>, linux-kernel@vger.kernel.org,
        Alexander Viro <viro@zeniv.linux.org.uk>,
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        Dan Williams <dan.j.williams@intel.com>,
        "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
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Subject: Re: [PATCH] dax: fix deadlock in __dax_fault
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On Fri, Sep 25, 2015 at 12:53:57PM +1000, Dave Chinner wrote:
<>
> We've already got block allocation serialisation at the filesystem
> level, and the issue is the unserialised block zeroing being done by
> the dax code. That can be fixed by moving the zeroing into the
> filesystem code when it runs "complete_unwritten" and checks whether
> the mapping has already been marked as written or not...
> 
> I've recently pointed out in a different thread that this is the
> solution to whatever that problem was (can't recall which
> thread/problem is was now :/ ) and it the same solution here. We
> already have the serialisation we need, we just need to move the
> block zeroing operation into the appropriate places to make it work
> correctly.

I think perhaps this is the thread that you're remembering:
https://lkml.org/lkml/2015/8/11/731