linux-kernel - Re: [PATCH] mm, numa: Fix bad pmd by atomically check for pmd_trans_huge when marking page tables prot

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Date:   Mon, 10 Apr 2017 08:38:24 -0400
From:   Rik van Riel <riel@...hat.com>
To:     Mel Gorman <mgorman@...hsingularity.net>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     Andrea Arcangeli <aarcange@...hat.com>,
        Michal Hocko <mhocko@...nel.org>,
        Vlastimil Babka <vbabka@...e.cz>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm, numa: Fix bad pmd by atomically check for
 pmd_trans_huge when marking page tables prot_numa

On Mon, 2017-04-10 at 10:48 +0100, Mel Gorman wrote:
> 
> While this could be fixed with heavy locking, it's only necessary to
> make a copy of the PMD on the stack during change_pmd_range and avoid
> races. A new helper is created for this as the check if quite subtle
> and the
> existing similar helpful is not suitable. This passed 154 hours of
> testing
> (usually triggers between 20 minutes and 24 hours) without detecting
> bad
> PMDs or corruption. A basic test of an autonuma-intensive workload
> showed
> no significant change in behaviour.
> 
> Signed-off-by: Mel Gorman <mgorman@...hsingularity.net>
> Cc: stable@...r.kernel.org

Acked-by: Rik van Riel <riel@...hat.com>