From: Hugh Dickins <hugh@veritas.com>

remove_mapping() must check against page_mapping(page):
&swapper_space is implicit, never actually stored in page->mapping.

Signed-off-by: Hugh Dickins <hugh@veritas.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
---

 mm/vmscan.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff -puN mm/vmscan.c~mm-remove_mapping-safeness-fix mm/vmscan.c
--- a/mm/vmscan.c~mm-remove_mapping-safeness-fix
+++ a/mm/vmscan.c
@@ -378,7 +378,7 @@ static pageout_t pageout(struct page *pa
 int remove_mapping(struct address_space *mapping, struct page *page)
 {
 	BUG_ON(!PageLocked(page));
-	BUG_ON(mapping != page->mapping);
+	BUG_ON(mapping != page_mapping(page));
 
 	write_lock_irq(&mapping->tree_lock);
 
_