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Date: Tue, 21 Nov 2017 14:12:13 -0800
From: Andrew Morton <akpm@linux-foundation.org>
To: Zi Yan <zi.yan@sent.com>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        Zi Yan <zi.yan@cs.rutgers.edu>, Andrea Reale <ar@linux.vnet.ibm.com>,
        Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>,
        =?ISO-8859-1?Q?J=E9r=F4me?= Glisse <jglisse@redhat.com>,
        stable@vger.kernel.org
Subject: Re: [PATCH] mm: migrate: fix an incorrect call of
 prep_transhuge_page()
Message-Id: <20171121141213.89db86bfbd75c22fc0209990@linux-foundation.org>
In-Reply-To: <20171121021855.50525-1-zi.yan@sent.com>
References: <20171121021855.50525-1-zi.yan@sent.com>
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On Mon, 20 Nov 2017 21:18:55 -0500 Zi Yan <zi.yan@sent.com> wrote:

> In [1], Andrea reported that during memory hotplug/hot remove
> prep_transhuge_page() is called incorrectly on non-THP pages for
> migration, when THP is on but THP migration is not enabled.
> This leads to a bad state of target pages for migration.
> 
> This patch fixes it by only calling prep_transhuge_page() when we are
> certain that the target page is THP.

What are the user-visible effects of the bug?