Re: WAPBL and backwards compatibility

[Michael Lorenz <macallan%netbsd.org@localhost>]

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Hello,

On Aug 1, 2008, at 03:22, Simon Burge wrote:

> There's a couple of issues here:
>
>  - Currently an old fsck will not know of the existance of the  
> journal.
>    If it sees a filesystem that wasn't unmounted cleanly with WAPBL
>    active it will just think it was a "normal" crash and repair it  
> as it
>    normally would.  The problem is that next time you use a WAPBL- 
> aware
>    kernel or fsck_ffs will see the untouched dirty journal and replay
>    it, possibly (probably?) causing damage.

Wouldn't the filesystem itself be marked clean in this case? At least  
if the non-wapbl kernel shuts down cleanly? In that case the log- 
aware fsck could just clean the log. If the non-wapbl kernel crashes  
we'd end up with a dirty log that doesn't match the dirty filesystem.

Something completely different but related - when I mount an  
APPLE_UFS filesystem with -o log it apparently creates the log and  
seems to Just Work but after a crash instead or replaying the log I  
get a normal fsck while an FFSv2 partition on the same disk gets the  
log replay treatment.
While I care less and less about MacOS X on this machine I'd like to  
know if this can be fixed, either by refusing to mount APPLE_UFS  
partitions with -o log or by making the journaling code work with it.

have fun
Michael

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