linux-kernel - Re: [PATCH] [RFC] UBI: Implement Fastmap support

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Message-ID: <4FC8768E.1010703@nod.at>
Date:	Fri, 01 Jun 2012 10:00:14 +0200
From:	Richard Weinberger <richard@....at>
To:	Adrian Hunter <adrian.hunter@...el.com>
CC:	linux-mtd@...ts.infradead.org, tglx@...utronix.de,
	dedekind1@...il.com, linux-kernel@...r.kernel.org,
	Heinz.Egger@...utronix.de, tim.bird@...sony.com
Subject: Re: [PATCH] [RFC] UBI: Implement Fastmap support

Am 01.06.2012 07:47, schrieb Adrian Hunter:
> It looks like, if you lose power at this point, the old fastmap may have
> been erased but the new fastmap has not been written.  That would mean
> you lose the fastmap.  Is that correct?  I guess you need to write the
> new fastmap first and then erase the old one.

True. But why is this a problem?
If we can recovers using a full scan after a power cut we are fine.
By deleting the old fastmap after writing the new one we may run out of free PEBs.
E.g: Assume a fastmap needs 4 PEBs and we have only 2 PEBs available the current approach works fine
because after returning and deleting the old fastmap we have 6 PEBs available and can write the new one.

Thanks,
//richard

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