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From:   Bobby Powers <bobbypowers@gmail.com>
Date:   Mon, 17 Feb 2020 19:59:12 -0800
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Subject: Re: [PATCH v5 00/25] userfaultfd: write protection support
To:     Peter Xu <peterx@redhat.com>
Cc:     linux-mm@kvack.org,
        Kernel development list <linux-kernel@vger.kernel.org>,
        David Hildenbrand <david@redhat.com>,
        Hugh Dickins <hughd@google.com>,
        Maya Gokhale <gokhale2@llnl.gov>,
        Jerome Glisse <jglisse@redhat.com>,
        Pavel Emelyanov <xemul@virtuozzo.com>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Martin Cracauer <cracauer@cons.org>,
        Denis Plotnikov <dplotnikov@virtuozzo.com>,
        Shaohua Li <shli@fb.com>,
        Andrea Arcangeli <aarcange@redhat.com>,
        Mike Kravetz <mike.kravetz@oracle.com>,
        Marty McFadden <mcfadden8@llnl.gov>,
        Mike Rapoport <rppt@linux.vnet.ibm.com>,
        Mel Gorman <mgorman@suse.de>,
        "Kirill A . Shutemov" <kirill@shutemov.name>,
        "Dr . David Alan Gilbert" <dgilbert@redhat.com>
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On Wed, Jun 19, 2019 at 7:20 PM Peter Xu <peterx@redhat.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@gmail.com>