linux-kernel - Re: [PATCH -mm] mm, pagemap: Fix soft dirty marking for PMD migration entry

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Message-ID: <20171017112100.pciya6pmo62owpht@node.shutemov.name>
Date:   Tue, 17 Oct 2017 14:21:00 +0300
From:   "Kirill A. Shutemov" <kirill@...temov.name>
To:     "Huang, Ying" <ying.huang@...el.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, Michal Hocko <mhocko@...e.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        David Rientjes <rientjes@...gle.com>,
        Arnd Bergmann <arnd@...db.de>, Hugh Dickins <hughd@...gle.com>,
        Jérôme Glisse <jglisse@...hat.com>,
        Daniel Colascione <dancol@...gle.com>,
        Zi Yan <zi.yan@...rutgers.edu>,
        Naoya Horiguchi <n-horiguchi@...jp.nec.com>
Subject: Re: [PATCH -mm] mm, pagemap: Fix soft dirty marking for PMD
 migration entry

On Tue, Oct 17, 2017 at 04:18:18PM +0800, Huang, Ying wrote:
> From: Huang Ying <ying.huang@...el.com>
> 
> Now, when the page table is walked in the implementation of
> /proc/<pid>/pagemap, pmd_soft_dirty() is used for both the PMD huge
> page map and the PMD migration entries.  That is wrong,
> pmd_swp_soft_dirty() should be used for the PMD migration entries
> instead because the different page table entry flag is used.
> 
> Cc: Michal Hocko <mhocko@...e.com>
> Cc: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
> Cc: David Rientjes <rientjes@...gle.com>
> Cc: Arnd Bergmann <arnd@...db.de>
> Cc: Hugh Dickins <hughd@...gle.com>
> Cc: "Jérôme Glisse" <jglisse@...hat.com>
> Cc: Daniel Colascione <dancol@...gle.com>
> Cc: Zi Yan <zi.yan@...rutgers.edu>
> Cc: Naoya Horiguchi <n-horiguchi@...jp.nec.com>
> Signed-off-by: "Huang, Ying" <ying.huang@...el.com>

What is effect of the misbehaviour? pagemap reports garbage?

Shoudn't it be in stable@? And maybe add Fixes: <sha1>.

Otherwise, looks good to me.

Acked-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>

-- 
 Kirill A. Shutemov