From: Andy Whitcroft <apw@shadowen.org>

As pointed out by Christop Lameter it should not be possible for a page to
change its active/inactive state without taking the lru_lock.  Reinstate this
safety net.

Signed-off-by: Andy Whitcroft <apw@shadowen.org>
Acked-by: Mel Gorman <mel@csn.ul.ie>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/vmscan.c |    7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff -puN mm/vmscan.c~lumpy-back-out-removal-of-active-check-in-isolate_lru_pages mm/vmscan.c
--- a/mm/vmscan.c~lumpy-back-out-removal-of-active-check-in-isolate_lru_pages
+++ a/mm/vmscan.c
@@ -683,10 +683,13 @@ static unsigned long isolate_lru_pages(u
 			nr_taken++;
 			break;
 
-		default:
-			/* page is being freed, or is a missmatch */
+		case -EBUSY:
+			/* else it is being freed elsewhere */
 			list_move(&page->lru, src);
 			continue;
+
+		default:
+			BUG();
 		}
 
 		if (!order)
_