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From: Terry Lambert <terry@lambert.org>
Message-Id: <199509131801.LAA07814@phaeton.artisoft.com>
Subject: Re: Is nullfs broken in -current?
To: wollman@lcs.mit.edu (Garrett A. Wollman)
Date: Wed, 13 Sep 1995 11:01:43 -0700 (MST)
Cc: terry@lambert.org, current@freefall.freebsd.org
In-Reply-To: <9509131756.AA02082@halloran-eldar.lcs.mit.edu> from "Garrett A. Wollman" at Sep 13, 95 01:56:52 pm
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> >> > # mount -t null -o union /dsk2/src1 /usr/src
> >> > # mount -t null -o union /dsk3/src2 /usr/src
> >> > # cd /usr/src
> >> > # make world
> 
> > This one is a unionfs, not a nullfs.
> 
> No, it is NOT a bloody unionfs!  `unionfs' == ``translucent
> filesystem''.  This is a nullfs using the `union mount' mechanism.
> BIG DIFFERENCE.

What is the effective operational difference?

It seems to me that the problem in this case is not as clear cut unless
we assume all problems when using nullfs come from a single line of
code.

The other example only exercises the nullfs itself instead of the nullfs
and the unioning code.


I already now the unioning code is broken; it has warts in various file
systems (but not in all of them) for lookup aliasing.

It looks like it would break for UFS rename, two places in msdosfs, and
in the explicit unionfs usage in anycase because of the relookup()
bogosity.


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