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Subject: Re: ubifs : corruption after power cut test
From: Artem Bityutskiy <dedekind1@gmail.com>
To: Matthieu CASTET <matthieu.castet@parrot.com>
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Date: Wed, 04 Aug 2010 19:14:57 +0300
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On Mon, 2010-08-02 at 11:32 +0200, Matthieu CASTET wrote:
> Matthieu CASTET a écrit :
> > Hi,
> > 
> > Matthieu CASTET a écrit :
> >> Artem Bityutskiy a écrit :
> >> Ok thanks, I will run it
> >>
> >> When checking the code, I saw that switch_gc_head can set c->gc_lnum to -1.
> >>
> >> In ubifs_put_super, we set c->mst_node->gc_lnum to c->gc_lnum and write 
> >> master node.
> >> Can't ubifs_put_super run while switch_gc_head set gc_lnum to -1 ?
> >>
> > I manage to reproduce it with the backtrace [1].
> > 
> Waiting for a proper fix, I force recovery if gc_lnum to 

The workaround looks ok, but I still do not understand how we end up
with writing -1. The only place c->gc_lnum is set to -1 is in GC, but it
is then initialized properly, and only error can cause GC to return with
c->gc_lnum == -1, in which case we switch to R/O mode immediately.

Is your UBIFS identical to what I have in my 2.6.27 back-port tree?

Also, I will have really little time till the beginning of September, so
probably this will wait...

-- 
Best Regards,
Artem Bityutskiy (Артём Битюцкий)