slab: correctly handle __GFP_ZERO

Use the correct local variable when calling into the page allocator.  Local
`flags' can have __GFP_ZERO set, which causes us to pass __GFP_ZERO into the
page allocator, possibly from illegal contexts.  The page allocator will later
do prep_zero_page()->kmap_atomic(..., KM_USER0) from irq contexts and will
then go BUG.

Cc: Mike Galbraith <efault@gmx.de>
Acked-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/slab.c b/mm/slab.c
index bde271c..a684778 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -2776,7 +2776,7 @@
 	 * 'nodeid'.
 	 */
 	if (!objp)
-		objp = kmem_getpages(cachep, flags, nodeid);
+		objp = kmem_getpages(cachep, local_flags, nodeid);
 	if (!objp)
 		goto failed;