linux-kernel - Re: UBI fastmap updates

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Message-ID: <20120802165132.1bf1e5d7@spider.haslach.nod.at>
Date:	Thu, 2 Aug 2012 16:51:32 +0200
From:	Richard Weinberger <richard@....at>
To:	artem.bityutskiy@...ux.intel.com
Cc:	linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org,
	adrian.hunter@...el.com, Heinz.Egger@...utronix.de,
	thomas.wucher@...utronix.de, shmulik.ladkani@...il.com,
	tglx@...utronix.de, tim.bird@...sony.com, Marius.Mazarel@...l.ro,
	nyoushchenko@...sta.com
Subject: Re: UBI fastmap updates

Am Thu, 02 Aug 2012 17:29:01 +0300
schrieb Artem Bityutskiy <artem.bityutskiy@...ux.intel.com>:

> On Thu, 2012-08-02 at 16:15 +0200, Richard Weinberger wrote:
> > > If I understand correctly, it can be only because of a bug. If I
> > > am correct, could you please add a 'dump_stack()' to improve the
> > > error report?
> > > 
> > 
> > This can happen if all PEBs are used and fastmap is unable to find
> > (or produce) an empty one.
> 
> In which situations is this possible? Could you please give an
> example?
> 

Every time fastmap writes a new fastmap to the flash it tries to get a
new PEB and returns the old one (used for the old fastmap) back to the
WL sub-system.
If no free PEBs are available (E.g Volume is full or the erase worker
is too slow) ubi_wl_get_fm_peb() returns NULL and fastmap reuses the
currently used PEB.
In this situation ubi_wl_get_fm_peb() may trigger such an error message.
If think we should get rid of the message as this is not an error
condition. It's a well known execution path.
The only bad thing that happens in such a situation is that a PEB gets
reused.

BTW: Which version of fastmap are you testing?

Thanks,
//richard
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