valid_section 252 arch/arm64/mm/init.c if (!valid_section(__nr_to_section(pfn_to_section_nr(pfn)))) valid_section 1298 include/linux/mmzone.h return valid_section(__nr_to_section(nr)); valid_section 1352 include/linux/mmzone.h if (!valid_section(ms)) valid_section 501 mm/memory_hotplug.c if (WARN_ON_ONCE(!valid_section(ms)))