linux-kernel - Re: [PATCH v5 00/25] userfaultfd: write protection support

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Message-ID: <CAArOQ2Vbpyu=JGfWNgOSQbXe15WzAB6VSah1OV8Cbx99bf0AXA@mail.gmail.com>
Date:   Mon, 17 Feb 2020 19:59:12 -0800
From:   Bobby Powers <bobbypowers@...il.com>
To:     Peter Xu <peterx@...hat.com>
Cc:     linux-mm@...ck.org,
        Kernel development list <linux-kernel@...r.kernel.org>,
        David Hildenbrand <david@...hat.com>,
        Hugh Dickins <hughd@...gle.com>,
        Maya Gokhale <gokhale2@...l.gov>,
        Jerome Glisse <jglisse@...hat.com>,
        Pavel Emelyanov <xemul@...tuozzo.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Martin Cracauer <cracauer@...s.org>,
        Denis Plotnikov <dplotnikov@...tuozzo.com>,
        Shaohua Li <shli@...com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Marty McFadden <mcfadden8@...l.gov>,
        Mike Rapoport <rppt@...ux.vnet.ibm.com>,
        Mel Gorman <mgorman@...e.de>,
        "Kirill A . Shutemov" <kirill@...temov.name>,
        "Dr . David Alan Gilbert" <dgilbert@...hat.com>
Subject: Re: [PATCH v5 00/25] userfaultfd: write protection support

On Wed, Jun 19, 2019 at 7:20 PM Peter Xu <peterx@...hat.com> wrote:
> This series implements initial write protection support for
> userfaultfd.  Currently both shmem and hugetlbfs are not supported
> yet, but only anonymous memory.  This is the 4nd version of it.
>
> The latest code can also be found at:
>
>   https://github.com/xzpeter/linux/tree/uffd-wp-merged

Hi Peter - I ported the branch you had above on top of v5.4.20 (what I
happened to be running locally), and fixed one issue that was causing
crashes for me:
https://github.com/bpowers/linux/commit/61086b5a0fa4aeb494e86d999926551a4323b84f

I wrote a small test program here:
https://github.com/plasma-umass/Mesh/blob/master/src/test/userfaultfd-kernel-copy.cc
and write protection support for userfaultfd (with eventual shmem
support) would be _hugely_ helpful for a userspace memory allocator
I'm working on.

Is there anything I can do to help get this considered for mainline?
We have some time before the 5.7 merge window opens up.

Tested-by: Bobby Powers <bobbypowers@...il.com>