Exactly. But for hugetlbfs/shmem ("!RAM-backed files") this is not what we want.OK, then I must have misread your requirements. Maybe I just got lost in all the combinations you have listed.
Another special case could be dax/pmem I think. You might want to fault it in readable/writable but not perform an actual read/write unless really required.
QEMU phrases this as "don't cause wear on the storage backing". -- Thanks, David / dhildenb