Date: Thu, 10 Mar 2005 13:05:48 +0100 From: Jeremie Le Hen <jeremie@le-hen.org> To: Denis Shaposhnikov <dsh@vlink.ru> Cc: freebsd-current@FreeBSD.ORG Subject: Re: unionfs 5.4 Message-ID: <20050310120548.GL34822@obiwan.tataz.chchile.org> In-Reply-To: <87r7it18fh.fsf@neva.vlink.ru> References: <87is46kzk1.fsf@neva.vlink.ru> <41C26F23F7DF023CB3DF35C5@cc-171.int.t-online.fr> <87sm3ajj8s.fsf@neva.vlink.ru> <20050305151903.GC26240@hub.freebsd.org> <87r7it18fh.fsf@neva.vlink.ru>
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> And if unionfs panic the system on 5.4 too, I think it can't be STABLE > at all. > > BTW, from man mount_nullfs: > > BUGS > THIS FILE SYSTEM TYPE IS NOT YET FULLY SUPPORTED (READ: IT DOESN'T WORK) > AND USING IT MAY, IN FACT, DESTROY DATA ON YOUR SYSTEM. USE AT > YOUR OWN RISK. BEWARE OF DOG. SLIPPERY WHEN WET. > > So you can't suggest to use nullfs instead of unionfs, because "is > well-documented to be broken". FYI, this is an email I just sent in reply to David Schultz on -hackers@. %%% Date: Thu, 10 Mar 2005 12:38:43 +0100 From: Jeremie Le Hen <jeremie@le-hen.org> To: David Schultz <das@FreeBSD.ORG> Cc: freebsd-fs@FreeBSD.ORG Cc: Mikhail Teterin <mi+mx@aldan.algebra.com> Cc: hackers@FreeBSD.ORG Hi David, > Nullfs works better than unionfs. Unionfs worked well in 4.X. > Despite numerous minor bugs such as being unable to cope with > FIFOs, several people have reported using it quite successfully on > production systems. However, unionfs no longer works quite as > well in 5.X or -CURRENT. There are several reasons for this: > > 1. Nobody seems to have both the time and interest to maintain it. > > 2. Developers can't be expected to prevent regressions in > something that's unsupported. > > 3. There are a couple of people who always respond to questions > about unionfs with comments along the lines of: > ``It's broken, so we won't help you. Go away and don't tell > us if you find any bugs.'' > > There's some pretty low-hanging fruit in terms of nits to fix. > See the PR database if you're interested in helping, and don't let > anyone scare you away. ;-) > > > What about the `union' option to regular mounts? Is that safe to use? > > Last I checked, it was very broken, but I'm not sure. A little time ago, phk@ asked for people to submit regression tests for virtual filesystem like this [1]. AFAIK, nobody submitted even one test so far. This could be a good starting point to have unionfs work correctly again. However, I think FreeBSD VFS gurus should first spread some ideas and clues about tests to do. I guess indeed there are very tricky ones that most common mortals wouldn't even suspect. Regards, [1] http://lists.freebsd.org/pipermail/freebsd-current/2005-January/045743.html -- Jeremie Le Hen < jeremie at le-hen dot org >< ttz at chchile dot org >
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