linux-kernel - [PATCH][BUGFIX] vmscan: limit VM

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Date:	Tue, 13 Oct 2009 16:00:54 +0800
From:	Wu Fengguang <fengguang.wu@...el.com>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	stable@...nel.org
Cc:	Rik van Riel <riel@...hat.com>,
	Christian Borntraeger <borntraeger@...ibm.com>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.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: [PATCH][BUGFIX] 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.

Tested-by: Christian Borntraeger <borntraeger@...ibm.com>
Reviewed-by: Rik van Riel <riel@...hat.com>
Signed-off-by: Wu Fengguang <fengguang.wu@...el.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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