linux-kernel - Re: [PATCH v6 1/2] mm: migration: fix migration of huge PMD shared pages

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Message-ID: <20180905065746.GY14951@dhcp22.suse.cz>
Date:   Wed, 5 Sep 2018 08:57:46 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Jerome Glisse <jglisse@...hat.com>
Cc:     Mike Kravetz <mike.kravetz@...cle.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
        Davidlohr Bueso <dave@...olabs.net>,
        Andrew Morton <akpm@...ux-foundation.org>,
        stable@...r.kernel.org, linux-rdma@...r.kernel.org,
        Matan Barak <matanb@...lanox.com>,
        Leon Romanovsky <leonro@...lanox.com>,
        Dimitri Sivanich <sivanich@....com>
Subject: Re: [PATCH v6 1/2] mm: migration: fix migration of huge PMD shared
 pages

On Tue 04-09-18 10:00:36, Jerome Glisse wrote:
> On Mon, Sep 03, 2018 at 07:56:54AM +0200, Michal Hocko wrote:
[...]
> > And THP migration is still a problem with 4.4 AFAICS. All other cases
> > simply split the huge page but THP migration keeps it in one piece and
> > as such it is theoretically broken as you have explained. So I would
> > stick with what I posted with some more clarifications in the changelog
> > if you think it is appropriate (suggestions welcome).
> 
> Reading code there is no THP migration in 4.4 only huge tlb migration.

Meh, you are right. For some reason I misread unmap_and_move_huge_page
to be also for THP. Sorry for the conusion. My fault!

Then it would be indeed safer to use your backport.
-- 
Michal Hocko
SUSE Labs