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Date: Mon, 2 Oct 2017 15:47:39 -0700
From: Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH v2 0/4] dax: require 'struct page' and other fixups
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To: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Chinner <david@fromorbit.com>, Christoph Hellwig <hch@lst.de>, Michal Hocko <mhocko@suse.com>, Jan Kara <jack@suse.cz>, "linux-nvdimm@lists.01.org" <linux-nvdimm@lists.01.org>, Linux MM <linux-mm@kvack.org>, Jeff Moyer <jmoyer@redhat.com>, linux-fsdevel <linux-fsdevel@vger.kernel.org>, Ross Zwisler <ross.zwisler@linux.intel.com>, "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>

On Sun, 1 Oct 2017 16:15:06 -0700 Dan Williams <dan.j.williams@intel.com> wrote:

> On Sun, Oct 1, 2017 at 2:59 PM, Dave Chinner <david@fromorbit.com> wrote:
> [..]
> > The "capacity tax" had nothing to do with it - the major problem
> > with self hosting struct pages was that page locks can be hot and
> > contention on them will rapidly burn through write cycles on the
> > pmem. That's still a problem, yes?
> 
> It was an early concern we had, but it has not born out in practice,
> and stopped worrying about it 2 years ago when the ZONE_DEVICE
> infrastructure was merged.

These are weighty matters and should have been covered in the
changelogs, please.  Could you send along a few paragraphs which
summarise these thoughts and I'll add them in?

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