linux-kernel - Re: oomkiller over-ambitious after "vmscan: make mapped executable pages the first class citizen" (bisected)

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Message-ID: <4AD3E6C4.805@redhat.com>
Date:	Mon, 12 Oct 2009 22:32:36 -0400
From:	Rik van Riel <riel@...hat.com>
To:	Wu Fengguang <fengguang.wu@...el.com>
CC:	Christian Borntraeger <borntraeger@...ibm.com>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Elladan <elladan@...imo.com>, Nick Piggin <npiggin@...e.de>,
	Andi Kleen <andi@...stfloor.org>,
	Christoph Lameter <cl@...ux-foundation.org>,
	Peter Zijlstra <peterz@...radead.org>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Minchan Kim <minchan.kim@...il.com>
Subject: Re: oomkiller over-ambitious after "vmscan: make mapped executable
 pages the first class citizen" (bisected)

Wu Fengguang wrote:

> vmscan: limit VM_EXEC protection to file pages
> 
> It is possible to have !Anon but SwapBacked pages, and some apps could
> create huge number of such pages with MAP_SHARED|MAP_ANONYMOUS. These
> pages go into the ANON lru list, and hence shall not be protected: we
> only care mapped executable files. Failing to do so may trigger OOM.

Good catch!  The MAP_SHARED|MAP_ANONYMOUS segments may
be backed by anonymous tmpfs files, instead of by
actual anonymous memory!

If this patch solves Christian's problem, I believe
it should get merged into Linus's tree ASAP.

> Reported-by: Christian Borntraeger <borntraeger@...ibm.com>
> Signed-off-by: Wu Fengguang <fengguang.wu@...el.com>

Reviewed-by: Rik van Riel <riel@...hat.com>

>  mm/vmscan.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> --- linux.orig/mm/vmscan.c	2009-10-13 09:49:05.000000000 +0800
> +++ linux/mm/vmscan.c	2009-10-13 09:49:37.000000000 +0800
> @@ -1356,7 +1356,7 @@ static void shrink_active_list(unsigned 
>  			 * IO, plus JVM can create lots of anon VM_EXEC pages,
>  			 * so we ignore them here.
>  			 */
> -			if ((vm_flags & VM_EXEC) && !PageAnon(page)) {
> +			if ((vm_flags & VM_EXEC) && page_is_file_cache(page)) {
>  				list_add(&page->lru, &l_active);
>  				continue;
>  			}


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