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Date:      Tue, 8 Dec 2009 12:30:23 +0100
From:      Erik Trulsson <ertr1013@student.uu.se>
To:        cronfy <cronfy@sprinthost.ru>
Cc:        freebsd-questions@freebsd.org
Subject:   Re: FreeBSD is too filesystem errors sensitive
Message-ID:  <20091208113023.GA1828@owl.midgard.homeip.net>
In-Reply-To: <4B1E33CF.1070309@sprinthost.ru>
References:  <4B1DF953.4050504@sprinthost.ru> <hfl7v5$f9j$1@ger.gmane.org> <4B1E2D40.9060900@sprinthost.ru> <20091208114509.B67127@gwdu60.gwdg.de> <4B1E33CF.1070309@sprinthost.ru>

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On Tue, Dec 08, 2009 at 02:09:03PM +0300, cronfy wrote:
> 
> >>>>  panics like 'freeing free block' or 'ffs_valloc: dup alloc'
> >>
> >> Is there a way to say "Dear kernel, don't panic, I'am holding your 
> >> hand, keep working please-please-please?" If so, can it lead to 
> >> complete filesystem corruption indeed or it is not so serious?
> >
> > Afaik you can't do this. And you shouldn't do if it'd be possible. The 
> > file system errors you mention above should not happen under any 
> > normal circumstances. They may happen after a crash caused by other 
> > reasons but should get repaired by fsck. The kernel cannot continue 
> > with such errors because the whole file system metadata cannot be 
> > trusted anymore until repaired.
> >
> Thanks.
> 
> What I can definitely state is that after reboot nothing will get any 
> better. I will have same filesystem with same errors + new errors that 
> appeared because soft-updates were not synced, and I will have fsck 
> running in background. I'd prefer to just start fsck in background, 
> skipping that annoying reboot phase ;-) Am I willing strange?

Background fsck can only handle a few, very specific, filsystem problems. 
(Basically situations where blocks are marked as being in use, even though
they are not really used by anything.  Softupdates is supposed to guarantee
that those are the only types of filesystem errors that can occur, but in
reality that guarantee does not always hold.)

If you have other instances of filesystem corruption (which includes
everything which can trigger a kernel panic) you need to use a foreground
fsck to fix it.


Personally I would recommend not using background fsck at all unless you
know exactly what you are doing and why.



-- 
<Insert your favourite quote here.>
Erik Trulsson
ertr1013@student.uu.se



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