PostgreSQL as a filesystem

This isn't a high-priority question.

I'm developing a hobby OS and I'm looking into file systems. I've
thought about writing my own, and that appeals, but I'm also very
interested in the database-as-a-filesystem paradigm. It would be nice
to not have to write all of the stuff that goes into the DBMS (e.g.
parsers, query schedulers, etc) myself.

So I was wondering what sort of filesystem requirements Postgre has.
For example, could I write a simple interface layer that just requests
blocks from the physical device and translate those into byte sets, or
does the DB actually require multiple files mapped by a larger file
system that maintains names, etc.

I guess my real question is how much file system support is really
required by the DBMS's disk routines. Please reply to
nadiasvertex(at)gmail(dot)com since I'm not subscribed to this list. Thanks in
advance!

-={C}=-