r296286:
  Remove filemon->lock wrappers.
r296470:
  Only call bwillwrite() for logging to vnodes, as other fo_write() calls do.
r296472:
  Require kldunload -f to unload.
r296473:
  Add missing break for r296472.
r296575:
  FILEMON_SET_FD: Disallow changing the fd.