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

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Message-ID: <20170223145623.GA855@node.shutemov.name>
Date:   Thu, 23 Feb 2017 17:56:23 +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 Wed, Feb 22, 2017 at 04:15:07PM +0100, Andrea Arcangeli wrote:
> On Tue, Feb 21, 2017 at 04:25:45PM +0300, Kirill A. Shutemov wrote:
> > 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.
> 
> That would be simpler agreed. The point of having an "unsafe" faster
> version was only for code running in page fault context where the
> additional check is unnecessary.

Well, I don't think that the cost of additional check is significant here.
And we can bring ->vm_ops a bit closer to ->vm_flags to avoid potential
cache miss.

-- 
 Kirill A. Shutemov