Sure -- until your system crashes and data is left in an inconsistent state because some of it was written to non-volatile storage and some of it wasn't and you

Sure -- until your system crashes and data is left in an inconsistent state because some of it was written to non-volatile storage and some of it wasn't and your OS had no concept of transactional consistency because mmap is a leaky abstraction. [UPDATE] I missed a crucial part of the problem setup, which is that the data is read-only. That obviously moots my objection.