mm: zone_reclaim: compaction: increase the high order pages in the watermarks

Prevent the scaling down to reduce the watermarks too much.
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>

mm/page_alloc.c

@@ -1896,7 +1896,8 @@ static bool __zone_watermark_ok(struct zone *z, unsigned int order,
 		free_pages -= z->free_area[o].nr_free << o;
 
 		/* Require fewer higher order pages to be free */
-		min >>= 1;
+		if (o < (pageblock_order >> 2))
+			min >>= 1;
 
 		if (free_pages <= min)
 			return false;