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Date: Thu, 15 Sep 2016 10:26:15 +0200
From: Christoph Hellwig <hch@lst.de>
To: Dan Williams <dan.j.williams@intel.com>
Cc: linux-mm@kvack.org, linux-nvdimm@ml01.01.org, david@fromorbit.com,
        linux-kernel@vger.kernel.org, npiggin@gmail.com, xfs@oss.sgi.com,
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Subject: Re: [PATCH v2 2/3] mm, dax: add VM_DAX flag for DAX VMAs
Message-ID: <20160915082615.GA9772@lst.de>
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On Wed, Sep 14, 2016 at 11:54:38PM -0700, Dan Williams wrote:
> The DAX property, page cache bypass, of a VMA is only detectable via the
> vma_is_dax() helper to check the S_DAX inode flag.  However, this is
> only available internal to the kernel and is a property that userspace
> applications would like to interrogate.

They have absolutely no business knowing such an implementation detail.