I'm not sure there's a non-annoying way to bridge the problem. The semantics are just so different that there's a lot of friction that needs to be handled somewhere. (What does O_DIRECT mean in this context? What happens when someone decides to store files that are never normally closed?)

In some ways, the problem mirrors OR mappers. A lot of common cases can be handled, but there are always situations where you're confronted with the fact that relational logic just doesn't map cleanly to OO (or hierarchic storage).