linux-kernel - Re: [PATCH] userfaultfd: hugetlbfs: add UFFDIO

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Message-ID: <20170221132545.GD13174@node.shutemov.name>
Date:   Tue, 21 Feb 2017 16:25:45 +0300
From:   "Kirill A. Shutemov" <kirill@...temov.name>
To:     Andrea Arcangeli <aarcange@...hat.com>
Cc:     Mike Kravetz <mike.kravetz@...cle.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Mike Rapoport <rppt@...ux.vnet.ibm.com>,
        "Dr. David Alan Gilbert" <dgilbert@...hat.com>,
        Hillf Danton <hillf.zj@...baba-inc.com>,
        Pavel Emelyanov <xemul@...allels.com>
Subject: Re: [PATCH] userfaultfd: hugetlbfs: add UFFDIO_COPY support for
 shared mappings

On Thu, Feb 16, 2017 at 07:41:00PM +0100, Andrea Arcangeli wrote:
> Kirill what's your take on making the registration checks stricter?
> If we would add a vma_is_anonymous_not_in_fault implemented like above
> vma_can_userfault would just need a
> s/vma_is_anonymous/vma_is_anonymous_not_in_fault/ and it would be more
> strict. khugepaged could be then converted to use it too instead of
> hardcoding this vm_flags check. Unless I'm mistaken I would consider
> such a change to the registration code, purely a cleanup to add a more
> strict check.

[sorry for later response]

I think more strict vma_is_anonymous() is a good thing.

But I don't see a point introducing one more helper. Let's just make the
existing helper work better.

-- 
 Kirill A. Shutemov