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Date: Thu, 25 Oct 2007 18:22:26 +1000 (EST)
From: Bruce Evans <brde@optusnet.com.au>
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Subject: Re: [ANN] 8-CURRENT,
 RELENG_7 and RELENG_6 have gotten latest ?unionfs improvements
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On Wed, 24 Oct 2007, Oliver Fromme wrote:

> Dmitry Marakasov <amdmi3@amdmi3.ru> wrote:
> > I was told long time ago that -ounion is even
> > more broken than unionfs.
>
> That's wrong.  The union mount option was _never_ really
> broken.  I'm using it for almost as long as FreeBSD exists.

I recently noticed the following bugs in -ounion (which I've
never used for anything except testing):

(1) It is broken for all file systems except ffs and ext2fs, since
     all (?) file systems now use nmount(2) and only these two file
     systems have "union" in their mount options list.  It is still in
     the global options list in mount/mntopts.h, but this is only used
     with mount(2).  The global options list in mount/mntopts.h has
     many bogus non-global options, and even the global options list
     in kern/vfs_mount.c has some bogus non-global options, but "union"
     actually is a global options.  ext2fs loves "union" more than
     ffs -- although its options list is less disordered than ffs's,
     it has enough disorder to have 2 copies of "union".
(2) After fixing (1) by not using nmount(2), following of symlinks works
     strangely for at least devfs:
     (a) a link foo -> zero (where zero doesn't exist in the underlying
 	file system) doesn't work.  mount(1) says that the lookup is
 	done in the mounted file system first.
     (b) a link foo -> ./zero works.  This is correct.  Now I wonder
 	if it would work if zero existed only in the underlying file
 	system.

Have you noticed these bugs?  (2) is presumably old.

Bruce