mm: page_alloc: increase __GFP_BITS_SHIFT to include __GFP_OTHER_NODE

__GFP_OTHER_NODE is used for NUMA allocations on behalf of other nodes.
It's supposed to be passed through from the page allocator to
zone_statistics(), but it never gets there as gfp_allowed_mask is not
wide enough and masks out the flag early in the allocation path.

The result is an accounting glitch where successful NUMA allocations
by-agent are not properly attributed as local.

Increase __GFP_BITS_SHIFT so that it includes __GFP_OTHER_NODE.

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Andi Kleen <ak@linux.intel.com>
Reviewed-by: Minchan Kim <minchan.kim@gmail.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Reviewed-by: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/gfp.h

@@ -92,7 +92,7 @@ struct vm_area_struct;
  */
 #define __GFP_NOTRACK_FALSE_POSITIVE (__GFP_NOTRACK)
 
-#define __GFP_BITS_SHIFT 23	/* Room for 23 __GFP_FOO bits */
+#define __GFP_BITS_SHIFT 24	/* Room for N __GFP_FOO bits */
 #define __GFP_BITS_MASK ((__force gfp_t)((1 << __GFP_BITS_SHIFT) - 1))
 
 /* This equals 0, but use constants in case they ever change */