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From: Terry Lambert <terry@lambert.org>
Message-Id: <199512041841.LAA04000@phaeton.artisoft.com>
Subject: Re: modloadable file system?
To: leisner@sdsp.mc.xerox.com (Marty Leisner)
Date: Mon, 4 Dec 1995 11:41:54 -0700 (MST)
Cc: freebsd-hackers@FreeBSD.org, freebsd-questions@FreeBSD.org
In-Reply-To: <9512041524.AA18658@gnu.mc.xerox.com> from "Marty Leisner" at Dec 4, 95 07:24:28 am
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> 
> Can I see an example of a modloadable file system?

/usr/src/lkm/cd9660
/usr/src/lkm/kernfs
/usr/src/lkm/mfs
/usr/src/lkm/msdos
/usr/src/lkm/nfs
/usr/src/lkm/nullfs
/usr/src/lkm/procfs
/usr/src/lkm/umapfs
/usr/src/lkm/union

There is no difference in the FS code between a loadable and a static
FS, with the following exceptions:

1)	A code switch stub for initialization, deinitialization, and
	status chacking.  This is an artifact of the default static
	FS initialization mechanism.

2)	You must have at least one static FS that contains all allowable
	VOP's.  This is an artificate of /ys/kern/vfs_init.c having a
	loop to count VOP's instead of an extern variable to set up
	the variable num_vops in vnode_if.c, where it really belongs.

> I assume we can support it?

Yes.

> Also, in the kernel source tree, what's the difference between
> ufs and ffs?  (aren't they the same thing?)

"UFS" is a set of common code used by both FFS and LFS (LFS is an FFS
derived log structured file system).  Like Veritas (VXFS), LFS uses
FFS directory structures and other shared code to get flexnames.


					Terry Lambert
					terry@lambert.org
---
Any opinions in this posting are my own and not those of my present
or previous employers.