Date: Thu, 25 Oct 2007 18:22:26 +1000 (EST) From: Bruce Evans <brde@optusnet.com.au> To: freebsd-stable@freebsd.org, freebsd-fs@freebsd.org, freebsd-current@freebsd.org, amdmi3@amdmi3.ru Subject: Re: [ANN] 8-CURRENT, RELENG_7 and RELENG_6 have gotten latest ?unionfs improvements Message-ID: <20071025180001.D87518@delplex.bde.org> In-Reply-To: <200710241316.l9ODGYfZ093701@lurza.secnetix.de> References: <200710241316.l9ODGYfZ093701@lurza.secnetix.de>
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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
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