PTRS_PER_PMD 526 arch/x86/include/asm/pgtable.h return (address >> PMD_SHIFT) & (PTRS_PER_PMD - 1); PTRS_PER_PMD 1548 include/linux/mm.h unsigned long mask = ~(PTRS_PER_PMD * sizeof(pmd_t) - 1);