SECTION_MAP_LAST_BIT 1266 include/linux/mmzone.h #define SECTION_MAP_MASK	(~(SECTION_MAP_LAST_BIT-1))
SECTION_MAP_LAST_BIT  318 mm/sparse.c    	BUILD_BUG_ON(SECTION_MAP_LAST_BIT > (1UL<<PFN_SECTION_SHIFT));