nnpfs/xfs tutorial

[Kristaps Johnson]

Hello everybody,

I've added changes mentioned in this thread along with a slew of related 
documentation.  This project, I think, is somewhat OT to arla-drinkers so 
I'll keep any additional releases local to the web site (unless requested 
otherwise, of course!).

http://sysjail.bsd.lv/xfsskel/

(notice the trailing slash...)

Errata?  Additions?  Questions?  I don't anticipate adding a great deal 
(unless I've missed something blinding).  Pending issues are (1) the 
pioctl interface and (2) ADVLOCK.  Not difficult to figure out.  I think 
enough data exists to build a rudimentary file-system (less PAG 
manipulation via pioctl, etc).

Errors exist.  They must be killed.

As per the mission of xfsskel, I think this provides a fairly detailed set 
of documents on building one's file-system atop NNPFS.

Some comments:

>>   - xfs_message_bulkgetnode?
>>
> Hm.  I don't have that.  Could be useful for windows readdir where you need
> the statinfo for all the nodes, too.  Or color-ls...
>
> Is it an OpenBSD invention, or did it use to be in mainline?  I know people
> have talked about it.

This structure doesn't appear anywhere in the OpenBSD 3.9 NNPFS sources 
(NNPFS_VERSION 18).  I gather that it's unused.

And last but certainly not least:

What does NNPFS mean?

Take care, and thanks again,
   Kristaps