later (can be worked on once integrated to NetBSD):
* userspace component
  + what happens if it forks & exits?
  + some watchdog-mechanism against userspace hangs?  makes no sense?
* support request coalescing
* make userspace node -> vnode mapping more efficient
* make userspace API-compatible with FUSE
* investigate replacing handwritten ops with automatically generated ones
  (at least some of them, not possible for all, e.g. lookup())
  + this could have several positive implications, not just easier
    maintainability
* revisit mount and unmount code: audit for race conditions especially
  when called from vfs or fops simultaneously
  + look more closely at anything that touches pi_lock, actually
* file system "starter kit", i.e. tools to generate a skeleton fs
* play with buffers, name caching, etcetc.
* support update time modifcations for files in libpuffs
* support file size accounting in libpuffs