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Date: Mon, 28 Aug 2017 13:37:58 -0700 (PDT)
From: David Rientjes <rientjes@google.com>
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To: Mel Gorman <mgorman@techsingularity.net>
cc: Andrew Morton <akpm@linux-foundation.org>,
        "Hansen, Dave" <dave.hansen@intel.com>,
        "Luck, Tony" <tony.luck@intel.com>, Linux MM <linux-mm@kvack.org>,
        LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] mm, madvise: Ensure poisoned pages are removed from
 per-cpu lists
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On Mon, 28 Aug 2017, Mel Gorman wrote:

> Wendy Wang reported off-list that a RAS HWPOISON-SOFT test case failed and
> bisected it to the commit 479f854a207c ("mm, page_alloc: defer debugging
> checks of pages allocated from the PCP"). The problem is that a page that
> was poisoned with madvise() is reused. The commit removed a check that
> would trigger if DEBUG_VM was enabled but re-enabling the check only
> fixes the problem as a side-effect by printing a bad_page warning and
> recovering.
> 
> The root of the problem is that a madvise() can leave a poisoned on
> the per-cpu list.  This patch drains all per-cpu lists after pages are
> poisoned so that they will not be reused. Wendy reports that the test case
> in question passes with this patch applied.  While this could be done in
> a targeted fashion, it is over-complicated for such a rare operation.
> 
> Fixes: 479f854a207c ("mm, page_alloc: defer debugging checks of pages allocated from the PCP")
> Reported-and-tested-by: Wang, Wendy <wendy.wang@intel.com>
> Cc: stable@kernel.org
> Signed-off-by: Mel Gorman <mgorman@techsingularity.net>

Acked-by: David Rientjes <rientjes@google.com>