From: Dan Williams <dan.j.williams@intel.com>
Subject: Re: dax pmd fault handler never returns to userspace
Date: Wed, 18 Nov 2015 13:57:24 -0800
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Cc: Ross Zwisler <ross.zwisler@linux.intel.com>,
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	Ross Zwisler <ross.zwisler@intel.com>,
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To: Toshi Kani <toshi.kani@hpe.com>
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On Wed, Nov 18, 2015 at 1:33 PM, Toshi Kani <toshi.kani@hpe.com> wrote:
> I am seeing a similar/same problem in my test.  I think the problem is that in
> case of a WP fault, wp_huge_pmd() -> __dax_pmd_fault() -> vmf_insert_pfn_pmd(),
> which is a no-op since the PMD is mapped already.  We need WP handling for this
> PMD map.
>
> If it helps, I have attached change for follow_trans_huge_pmd().  I have not
> tested much, though.

Interesting, I didn't get this far because my tests were crashing the
kernel.  I'll add this case the pmd fault test in ndctl.