MM_CONTEXT_LOCK_PMLEN
clear_bit(MM_CONTEXT_LOCK_PMLEN, &mm->context.flags);
set_bit(MM_CONTEXT_LOCK_PMLEN, &p->mm->context.flags);
if (test_bit(MM_CONTEXT_LOCK_PMLEN, &mm->context.flags) && mm->context.pmlen != pmlen) {