linux-kernel - Re: [PATCH 4/5] mm: fix cache mode of dax pmd mappings

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Date:   Tue, 6 Sep 2016 13:17:56 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Dan Williams <dan.j.williams@...el.com>
Cc:     linux-nvdimm@...1.01.org, Toshi Kani <toshi.kani@....com>,
        Matthew Wilcox <mawilcox@...rosoft.com>,
        Nilesh Choudhury <nilesh.choudhury@...cle.com>,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        linux-mm@...ck.org, Ross Zwisler <ross.zwisler@...ux.intel.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Kai Zhang <kai.ka.zhang@...cle.com>
Subject: Re: [PATCH 4/5] mm: fix cache mode of dax pmd mappings

On Tue, 06 Sep 2016 09:49:41 -0700 Dan Williams <dan.j.williams@...el.com> wrote:

> track_pfn_insert() is marking dax mappings as uncacheable.
> 
> It is used to keep mappings attributes consistent across a remapped range.
> However, since dax regions are never registered via track_pfn_remap(), the
> caching mode lookup for dax pfns always returns _PAGE_CACHE_MODE_UC.  We do not
> use track_pfn_insert() in the dax-pte path, and we always want to use the
> pgprot of the vma itself, so drop this call.
> 
> Cc: Ross Zwisler <ross.zwisler@...ux.intel.com>
> Cc: Matthew Wilcox <mawilcox@...rosoft.com>
> Cc: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Nilesh Choudhury <nilesh.choudhury@...cle.com>
> Reported-by: Kai Zhang <kai.ka.zhang@...cle.com>
> Reported-by: Toshi Kani <toshi.kani@....com>
> Cc: <stable@...r.kernel.org>
> Signed-off-by: Dan Williams <dan.j.williams@...el.com>

Changelog fails to explain the user-visible effects of the patch.  The
stable maintainer(s) will look at this and wonder "ytf was I sent
this".

After fixing that, 

Acked-by: Andrew Morton <akpm@...ux-foundation.org>