__DIRTY_BITS
extern inline pte_t pte_mkclean(pte_t pte) { pte_val(pte) &= ~(__DIRTY_BITS); return pte; }
extern inline pte_t pte_mkdirty(pte_t pte) { pte_val(pte) |= __DIRTY_BITS; return pte; }
#define _PAGE_TABLE (_PAGE_VALID | __DIRTY_BITS | __ACCESS_BITS)
#define _PAGE_CHG_MASK (_PFN_MASK | __DIRTY_BITS | __ACCESS_BITS)