[PATCH][BUGFIX] vmscan: limit VM_EXEC protection to file pages

[Wu Fengguang <fengguang.wu@intel.com>]

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@de.ibm.com>
Reviewed-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Wu Fengguang <fengguang.wu@intel.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;
 			}