linux-kernel - Re: [PATCH] mm, madvise: Ensure poisoned pages are removed from per-cpu lists

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

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@...el.com>
> Cc: stable@...nel.org
> Signed-off-by: Mel Gorman <mgorman@...hsingularity.net>

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