SECTIONS_PER_ROOT
#define SECTION_NR_TO_ROOT(sec) ((sec) / SECTIONS_PER_ROOT)
#define NR_SECTION_ROOTS DIV_ROUND_UP(NR_MEM_SECTIONS, SECTIONS_PER_ROOT)
#define SECTION_ROOT_MASK (SECTIONS_PER_ROOT - 1)
extern struct mem_section mem_section[NR_SECTION_ROOTS][SECTIONS_PER_ROOT];
struct mem_section mem_section[NR_SECTION_ROOTS][SECTIONS_PER_ROOT]
unsigned long array_size = SECTIONS_PER_ROOT *