From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S1752569AbdH2Lz3 (ORCPT <rfc822;w@1wt.eu>);
        Tue, 29 Aug 2017 07:55:29 -0400
Received: from mx2.suse.de ([195.135.220.15]:33635 "EHLO mx1.suse.de"
        rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP
        id S1752325AbdH2Lz1 (ORCPT <rfc822;linux-kernel@vger.kernel.org>);
        Tue, 29 Aug 2017 07:55:27 -0400
Subject: Re: [PATCH] mm, madvise: Ensure poisoned pages are removed from
 per-cpu lists
To: Mel Gorman <mgorman@techsingularity.net>,
        Andrew Morton <akpm@linux-foundation.org>
Cc: "Hansen, Dave" <dave.hansen@intel.com>,
        "Luck, Tony" <tony.luck@intel.com>, Linux MM <linux-mm@kvack.org>,
        LKML <linux-kernel@vger.kernel.org>
References: <20170828133414.7qro57jbepdcyz5x@techsingularity.net>
From: Vlastimil Babka <vbabka@suse.cz>
Message-ID: <26785aab-caa8-bbdd-dbce-28cd826a9359@suse.cz>
Date: Tue, 29 Aug 2017 13:55:26 +0200
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101
 Thunderbird/52.3.0
MIME-Version: 1.0
In-Reply-To: <20170828133414.7qro57jbepdcyz5x@techsingularity.net>
Content-Type: text/plain; charset=iso-8859-15
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On 08/28/2017 03:34 PM, 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: Vlastimil Babka <vbabka@suse.cz>

> ---
>  mm/madvise.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/mm/madvise.c b/mm/madvise.c
> index 23ed525bc2bc..4d7d1e5ddba9 100644
> --- a/mm/madvise.c
> +++ b/mm/madvise.c
> @@ -613,6 +613,7 @@ static int madvise_inject_error(int behavior,
>  		unsigned long start, unsigned long end)
>  {
>  	struct page *page;
> +	struct zone *zone;
>  
>  	if (!capable(CAP_SYS_ADMIN))
>  		return -EPERM;
> @@ -646,6 +647,11 @@ static int madvise_inject_error(int behavior,
>  		if (ret)
>  			return ret;
>  	}
> +
> +	/* Ensure that all poisoned pages are removed from per-cpu lists */
> +	for_each_populated_zone(zone)
> +		drain_all_pages(zone);
> +
>  	return 0;
>  }
>  #endif
> 
> --
> To unsubscribe, send a message with 'unsubscribe linux-mm' in
> the body to majordomo@kvack.org.  For more info on Linux MM,
> see: http://www.linux-mm.org/ .
> Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
>