PG_double_map 674 include/linux/page-flags.h return PageHead(page) && test_bit(PG_double_map, &page[1].flags); PG_double_map 680 include/linux/page-flags.h set_bit(PG_double_map, &page[1].flags); PG_double_map 686 include/linux/page-flags.h clear_bit(PG_double_map, &page[1].flags); PG_double_map 691 include/linux/page-flags.h return test_and_set_bit(PG_double_map, &page[1].flags); PG_double_map 697 include/linux/page-flags.h return test_and_clear_bit(PG_double_map, &page[1].flags);