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Date:      Sun, 15 Jan 2012 09:12:05 +0100
From:      Stefan Bethke <stb@lassitu.de>
To:        Joe Holden <jwhlists@gmail.com>
Cc:        freebsd-stable@freebsd.org
Subject:   Re: UFS corruption panic
Message-ID:  <3BCC7D95-F0BC-447D-9828-DD5B6A07A54A@lassitu.de>
In-Reply-To: <CAD-04WOKH6yb0tjcM=pu86kzTfFej%2Bc0E-v9AMC9VyEDn4HSOg@mail.gmail.com>
References:  <CAD-04WOKH6yb0tjcM=pu86kzTfFej%2Bc0E-v9AMC9VyEDn4HSOg@mail.gmail.com>

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Am 15.01.2012 um 05:20 schrieb Joe Holden:

> Guys....
>=20
> Is a panic **really** appropriate for a filesystem that isn't even in
> fstab?
>=20
> ie;
> panic: ufs_dirbad: /mnt: bad dir ino 3229 at offset 0: mangled entry
>=20
> Which happened to be an file-backed md volume that got changed as I =
forgot
> to unmount it beforehand, however as a result there is now =
inconsistencies
> and probably data corruption or even missing data on other important
> filesystems (ie; /, /var etc) because there wasn't even a sync or any =
kind
> of other sensible behaviour.

Yes, a panic is the correct action here.  While I agree that it's super =
annoying, the filesystem notices that something is *really* wrong.  =
Instead of letting the problem fester and continue to corrupt data, it =
stops the system.

Most filesystems work under the assumption that they're the sole owner =
of the disk.  This means that any changes to the on-disk data must come =
from filesystem code itself; if that data is inconstistent, it must be a =
bug in the filesystem code.  At this point, panic is the only course of =
action to avoid even greater damage to the data.

In other words: don't do that then :-)


Stefan

--=20
Stefan Bethke <stb@lassitu.de>   Fon +49 151 14070811






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