linux-kernel - Re: [PATCH] mprotect: drop overprotective lock_pte

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Message-Id: <20170207134454.7af755ae379ca9d016b5c15a@linux-foundation.org>
Date:   Tue, 7 Feb 2017 13:44:54 -0800
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Cc:     Andrea Arcangeli <aarcange@...hat.com>,
        Mel Gorman <mgorman@...hsingularity.net>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mprotect: drop overprotective lock_pte_protection()

On Tue,  7 Feb 2017 17:33:47 +0300 "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com> wrote:

> lock_pte_protection() uses pmd_lock() to make sure that we have stable
> PTE page table before walking pte range.
> 
> That's not necessary. We only need to make sure that PTE page table is
> established. It cannot vanish under us as long as we hold mmap_sem at
> least for read.
> 
> And we already have helper for that -- pmd_trans_unstable().

http://ozlabs.org/~akpm/mmots/broken-out/mm-mprotect-use-pmd_trans_unstable-instead-of-taking-the-pmd_lock.patch
already did this?