PFN_SECTION_SHIFT
#define MAX_FOLIO_ORDER PFN_SECTION_SHIFT
#define PAGES_PER_SECTION (1UL << PFN_SECTION_SHIFT)
((1UL << (PFN_SECTION_SHIFT - pageblock_order)) * NR_PAGEBLOCK_BITS)
return pfn >> PFN_SECTION_SHIFT;
return sec << PFN_SECTION_SHIFT;
BUILD_BUG_ON(SECTION_MAP_LAST_BIT > PFN_SECTION_SHIFT);