mm: recheck page index in find_get_pages_contig

From: Konstantin Khlebnikov <khlebnikov@openvz.org>

Signed-off-by: Konstantin Khlebnikov <khlebnikov@openvz.org>
---
 mm/filemap.c |    1 +
 1 file changed, 1 insertion(+)

diff --git a/mm/filemap.c b/mm/filemap.c
index 79c4b2b..b3a698e 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -933,6 +933,7 @@ repeat:
 			break;
 		}
 
+		WARN_ON(page->index != index + ret);
 		pages[ret] = page;
 		if (++ret == nr_pages)
 			break;