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From: "Huang\, Ying" <ying.huang@intel.com>
To: Zi Yan <zi.yan@cs.rutgers.edu>
Cc: "Huang\, Ying" <ying.huang@intel.com>,
        "Kirill A. Shutemov" <kirill@shutemov.name>,
        Andrew Morton <akpm@linux-foundation.org>, <linux-mm@kvack.org>,
        <linux-kernel@vger.kernel.org>, Michal Hocko <mhocko@suse.com>,
        "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        David Rientjes <rientjes@google.com>, Arnd Bergmann <arnd@arndb.de>,
        Hugh Dickins <hughd@google.com>,
        =?utf-8?B?Su+/vXLvv71tZQ==?= Glisse <jglisse@redhat.com>,
        Daniel Colascione <dancol@google.com>,
        Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Subject: Re: [PATCH -mm] mm, pagemap: Fix soft dirty marking for PMD migration entry
References: <20171017081818.31795-1-ying.huang@intel.com>
        <20171017112100.pciya6pmo62owpht@node.shutemov.name>
        <874lqy7yks.fsf@yhuang-dev.intel.com> <59E5F881.20105@cs.rutgers.edu>
Date: Tue, 17 Oct 2017 21:55:12 +0800
In-Reply-To: <59E5F881.20105@cs.rutgers.edu> (Zi Yan's message of "Tue, 17 Oct
        2017 08:33:05 -0400")
Message-ID: <87vajd7ubj.fsf@yhuang-dev.intel.com>
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Zi Yan <zi.yan@cs.rutgers.edu> writes:

> Huang, Ying wrote:
>> "Kirill A. Shutemov" <kirill@shutemov.name> writes:
>> 
>>> On Tue, Oct 17, 2017 at 04:18:18PM +0800, Huang, Ying wrote:
>>>> From: Huang Ying <ying.huang@intel.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@suse.com>
>>>> Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
>>>> Cc: David Rientjes <rientjes@google.com>
>>>> Cc: Arnd Bergmann <arnd@arndb.de>
>>>> Cc: Hugh Dickins <hughd@google.com>
>>>> Cc: "J.r.me Glisse" <jglisse@redhat.com>
>>>> Cc: Daniel Colascione <dancol@google.com>
>>>> Cc: Zi Yan <zi.yan@cs.rutgers.edu>
>>>> Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
>>>> Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
>>> What is effect of the misbehaviour? pagemap reports garbage?
>> 
>> Yes.  pagemap may report incorrect soft dirty information for PMD
>> migration entries.
>
> Thanks for fixing it.
>
>> 
>>> Shoudn't it be in stable@? And maybe add Fixes: <sha1>.
>> 
>> Yes.  Will do that in the next version.
>
> PMD migration is merged in 4.14, which is not final yet. Do we need to
> split the patch, so that first hunk(for present PMD entries) goes into
> stable and second hunk(for PMD migration entries) goes into 4.14?

Oh, if so, I think we don't need to back port it to stable kernel.  But
we still need Fixes: tag.

Best Regards,
Huang, Ying