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Date: Mon, 9 Apr 2018 17:47:53 -0700
From: Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH -mm] mm, pagemap: Fix swap offset value for PMD
 migration entry
Message-Id: <20180409174753.4b959a5b3ff732b8f96f5a14@linux-foundation.org>
In-Reply-To: <20180408033737.10897-1-ying.huang@intel.com>
References: <20180408033737.10897-1-ying.huang@intel.com>
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Sender: owner-linux-mm@kvack.org
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To: "Huang, Ying" <ying.huang@intel.com>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Michal Hocko <mhocko@suse.com>, "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>, Andrei Vagin <avagin@openvz.org>, Dan Williams <dan.j.williams@intel.com>, Jerome Glisse <jglisse@redhat.com>, Daniel Colascione <dancol@google.com>, Zi Yan <zi.yan@cs.rutgers.edu>, Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>

On Sun,  8 Apr 2018 11:37:37 +0800 "Huang, Ying" <ying.huang@intel.com> wrote:

> From: Huang Ying <ying.huang@intel.com>
> 
> The swap offset reported by /proc/<pid>/pagemap may be not correct for
> PMD migration entry.  If addr passed into pagemap_range() isn't

pagemap_pmd_range(), yes?

> aligned with PMD start address,

How can this situation come about?

> the swap offset reported doesn't
> reflect this.  And in the loop to report information of each sub-page,
> the swap offset isn't increased accordingly as that for PFN.
> 
> BTW: migration swap entries have PFN information, do we need to
> restrict whether to show them?

For what reason?  Address obfuscation?