Date: Fri, 30 Aug 1996 09:05:51 +0200 (MET) From: "Jesus A. Mora Marin" <amora@obelix.cica.es> To: terry@lambert.org (Terry Lambert) Cc: dyson@iquest.net, jkh@time.cdrom.com, freebsd-fs@freebsd.org Subject: Re: s5 filesys implementation? Message-ID: <199608300705.JAA02749@obelix.cica.es> In-Reply-To: <199608271612.JAA24806@phaeton.artisoft.com> from "Terry Lambert" at Aug 27, 96 09:12:58 am
next in thread | previous in thread | raw e-mail | index | archive | help
I'll try to answer to everybody with this.
Terry Lambert <terry@lambert.org> said:
> This is onmy list of "to do" items. I was an engineer for Novell/USG
> (USL) who worked on, among other things, kernel FS code.
Glad to meet you, Terry. I didn't mean to jeopardize anyone's 'to-do' list :)
> If you are planning on working on FS code in the very near future,
> then I'd say go ahead. Otherwise, I hope the lanscape will be changing
> pretty radically pretty soon -- if you have done enough FS work that
> you can abstract framework components from implementation, then you
> should be pretty safe for any long term projects that you want to
> pursue.
>
> You may want to consider holding off until the Lite2 integration has
> been completed; since it changes some of the architecture. I don't
> think it;s safe to assume that the changes from that direction are
> done either.
>
> Your best bet would be to get in contact with David Greenman or John
> Dyson, since they make architectural decisions, and the FS is one
> place that will be hit (one way or the other) by almost all
> architectural changes.
Argh! Can you please stop messing a while? I can imagine the picture: a red
light starts to blink at the FreeBSD Hackers Command Center. "Hey! Jesus has
got a minimal understanding about proc scheduling. Let's change all the stuff
right now!" :)
Now serious. My main objective with this project is educational. I've been
studying the implementation of VFS in SysVR4, and was appealed by its design.
Just for fun, I took the FreeBSD code for this subsystem and saw it's organized
in a very similar way, if not identical. Furthermore, this code seemed rather
clear to me, so I have decided to try a practical approach. I know that support
for sysv fs is not a very useful thing, but it's not implemented yet and
I've been living with it for many years. sysv fs is not a very sophisticated
one and has a very simple organization, so fs-dependent code would not be
very painful to write. Also, inode struct is almost identical to that of ffs,
and no anaesthetical tricks are needed as those required when you deal with
msdosfs, so the implementation should be clean. For some time, I was considering
simply to port the code in Linux, but I was not aware of how it performs, nor
that its integration in FreeBSD is a straightforward task. So I've decided to
start from scratch, but I don't discard to "borrow" some ideas from the Linux
code -with its author's consent, of course-.
Now, an overview of what I plan is:
*) Further learning of the vfs subsystem in FreeBSD, and its interface with
fs-dependent code. This phase does not necessarily precedes the others,
but overlaps them (crashes teach a lot :)
1) Implementation of fs type dependent VFS ops, ie s5fs_mount(), s5fs_sync(),
and so on. I should begin this right now. I'd start working with SCO Unix
SVR3 filesys in diskettes only. If I become confident enough, I could
install an old SCO Unix version in my HD. I think that giving support for
xenix filesystems could be considered, if I find any diskette to work with.
User-level mount_s5 command must be avaible at this point. Funny, you can
(u)mount it, stat it, but no more :) Anyway, I guess this stage won't
take more than a few days.
2) Implementation of fs type dependent vnode ops, (s5fs_open/close, _read/write,
...). I must consider which functions to implement and which ones are
nonsensical in a non-primary filesystem type. Suggestions appreciated.
3) Writing additional user-level commands: fsck_s5, mkfs_s5, fsdb_s5?
4) Last but not least: trying to write a doc describing the design and internals
of FreeBSD VFS subsystem, and my own experiences with s5 support
implementation. It could be a potential contribution to the Documentation
Project, that is, given it worths its space in disk and if some masochist
volunteer translates my weird "English" into a correct one. Should I get
just this one, I will be happy.
You can see, I am not a Unix guru, nor a hacker, but I will do my best this
time. Also, I hope you will lend me a hand when needed -I'll get stuck, you
can bet-.
BTW, John Dyson <dyson@iquest.net>:
> I suggest working with the Aug snapshot or later.
What's the most recent snapshot stable enough? I run 2.2-960326SNAP at job and
had no problems with it. At home, I run 2.1-RELEASE, and received 2.1.5-RELEASE
yesterday, but I'm considering to jump to a 2.2-SNAP. Please info and I'll
order.
So please, hints? suggestions? discouraging comments? funds (cash only please)?
Jesus A. Mora
amora@obelix.cica.es
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?199608300705.JAA02749>