linux-kernel - Re: [PATCH 6/7] mm, fs: introduce file_operations->post

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Message-ID: <CAPcyv4gXt673Jz2__t7LwvaFrRGxa5czgoB-b8kdjAfOETAH9Q@mail.gmail.com>
Date:   Wed, 27 Sep 2017 08:54:59 -0700
From:   Dan Williams <dan.j.williams@...el.com>
To:     Ross Zwisler <ross.zwisler@...ux.intel.com>,
        Jan Kara <jack@...e.cz>,
        Dan Williams <dan.j.williams@...el.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Darrick J. Wong" <darrick.wong@...cle.com>,
        "J. Bruce Fields" <bfields@...ldses.org>,
        Christoph Hellwig <hch@....de>,
        Dave Chinner <david@...morbit.com>,
        Jeff Layton <jlayton@...chiereds.net>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        Linux MM <linux-mm@...ck.org>,
        "linux-nvdimm@...ts.01.org" <linux-nvdimm@...ts.01.org>,
        linux-xfs@...r.kernel.org
Subject: Re: [PATCH 6/7] mm, fs: introduce file_operations->post_mmap()

On Wed, Sep 27, 2017 at 8:39 AM, Ross Zwisler
<ross.zwisler@...ux.intel.com> wrote:
> On Wed, Sep 27, 2017 at 01:35:27PM +0200, Jan Kara wrote:
[..]
>> Hum, this is an interesting option. So do you suggest that filesystems
>> supporting DAX would always setup mappings with VM_MIXEDMAP and without
>> VM_HUGEPAGE and thus we'd get rid of dependency on S_DAX flag in ->mmap?
>> That could actually work. The only possible issue I can see is that
>> VM_MIXEDMAP is still slightly different from normal page mappings and it
>> could have some performance implications - e.g. copy_page_range() does more
>> work on VM_MIXEDMAP mappings but not on normal page mappings.
>
> It looks like having VM_MIXEDMAP always set for filesystems that support DAX
> might affect their memory's NUMA migration in the non-DAX case?
>
> 8e76d4e sched, numa: do not hint for NUMA balancing on VM_MIXEDMAP mappings

Addressed separately here:

c1ef8e2c0235 mm: disable numa migration faults for dax vmas