Still in the process of experimenting with filesystems.

  I  have  some very simple prototypes running, for example a filesystem
  that stores exactly one file and no attributes. Sounds trivial, but  I
  learned a great deal.

  I'm  sorry  to  say,  though,  that documentation could be better. I'm
  mostly learning by doing guesswork and  reading  the  source  code  of
  minix  fs.  I  expected some clear specifications, like "this function
  will be run on $foo and must return $bar or $baz". Sometimes there are
  comments like that, yes, but I have lots and lots of questions.

  Not so easy ...

  (Yes, I could use FUSE, but that would be boring, wouldn't it? :-))

  My  goal  is  to have a simple but usable filesystem by the end of the
  year. It should be able to store files, directories, and  some  simple
  attributes (mtime and friends). Let's see how that goes.