Subject: Re: Log area on-disk for the journal
To: Pavel Cahyna <>
From: Bill Studenmund <>
List: tech-kern
Date: 10/22/2006 17:56:49
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On Sat, Oct 21, 2006 at 10:30:19AM +0200, Pavel Cahyna wrote:
> On Fri, Oct 20, 2006 at 01:37:05PM -0700, Jason Thorpe wrote:
> > >>  . compatibility/upgrade issues, such as whether the accessing
> > >>    filesystem code has to be journal aware, even if the filesystem
> > >>    was cleanly unmounted.
> >=20
> > Journaled UFS should get a new magic number.  Old tools will refuse to =
talk to=20
> > one in that case.
> Even if the filesystem is unmounted clenaly (does not need log recovery)?
> Disallowing access by old tools would be suboptimal in this case.

Why? If you are up-to-date enough to have a journaled file system, why=20
don't you have up-to-date tools?

Old tools don't know how to tell if a journal is dirty. Thus they can't=20
differentiate between a journaled file system that needs replay and one=20
that doesn't. So while it would be safe for such a tool to work on a=20
clean file system, it can blindly destroy a dirty one.

If we feel there's a need, once we have a stable implementation, I think=20
it would be fine to back-port the replay and fixup code to older NetBSD=20
branches. If we feel there's a need.

Take care,


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