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Re: WAPBL and backwards compatibility



On Sun, Aug 03, 2008 at 11:36:04AM -0400, Perry E. Metzger wrote:
> 
> Alan Barrett <apb%cequrux.com@localhost> writes:
> >> [2] Add a check in the current FFS WAPBL code (and fsck_ffs) to
> >>    explicitly not replay the log if the filesystem is marked as clean.
> >>    This would be on the assumption that something else has fixed it for
> >>    you since you last mounted it with a WAPBL-aware kernel.
> >
> > I think that we should do option 2 in the short term,
> 
> Couldn't that result in data loss, though?

Kinda. Note that part of this text describes a non-WAPBL tool "fixing" a 
WAPBL fs. That can result in data loss. So we are talking a matter of 
degrees. "Don't do that" is a good thing to shout.

This option ([2]) will be "ok" if a WAPBL fs never sets the clean bit if 
the journal needs replay.

We may also want another option, call it [5], where in we teach NetBSD-4 
(and NetBSD-3?) fsck enough about WAPBL to know they shouldn't touch it.
Obviously if we change the magic #, this doesn't matter.

Take care,

Bill

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