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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Message-Id: <20170411144402.1a2c0570173d12dc97012f5e@linux-foundation.org>
Date:   Tue, 11 Apr 2017 14:44:02 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Vlastimil Babka <vbabka@...e.cz>
Cc:     Zi Yan <zi.yan@...rutgers.edu>,
        Mel Gorman <mgorman@...hsingularity.net>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Rik van Riel <riel@...hat.com>,
        Michal Hocko <mhocko@...nel.org>, 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 Tue, 11 Apr 2017 08:35:02 +0200 Vlastimil Babka <vbabka@...e.cz> wrote:

> >> I have Kirrill's
> >>
> >> thp-reduce-indentation-level-in-change_huge_pmd.patch
> >> thp-fix-madv_dontneed-vs-numa-balancing-race.patch
> >> mm-drop-unused-pmdp_huge_get_and_clear_notify.patch
> >> thp-fix-madv_dontneed-vs-madv_free-race.patch
> >> thp-fix-madv_dontneed-vs-madv_free-race-fix.patch
> >> thp-fix-madv_dontneed-vs-clear-soft-dirty-race.patch
> >>
> >> scheduled for 4.12-rc1.  It sounds like
> >> thp-fix-madv_dontneed-vs-madv_free-race.patch and
> >> thp-fix-madv_dontneed-vs-madv_free-race.patch need to be boosted to
> >> 4.11 and stable?
> > 
> > thp-fix-madv_dontneed-vs-numa-balancing-race.patch is the fix for
> > numa balancing problem reported in this thread.
> > 
> > mm-drop-unused-pmdp_huge_get_and_clear_notify.patch,
> > thp-fix-madv_dontneed-vs-madv_free-race.patch,
> > thp-fix-madv_dontneed-vs-madv_free-race-fix.patch, and
> > thp-fix-madv_dontneed-vs-clear-soft-dirty-race.patch
> > 
> > are the fixes for other potential race problems similar to this one.
> > 
> > I think it is better to have all these patches applied.
> 
> Yeah we should get all such fixes to stable IMHO (after review :). It's
> not the first time that a fix for MADV_DONTNEED turned out to also fix a
> race that involved "normal operation" with THP, without such syscalls.

The presence of thp-reduce-indentation-level-in-change_huge_pmd.patch
is a pain in the ass but I've decided to keep it rather than churning
all the patches at a late stage.