linux-kernel - Re: [PATCH] UBI: vtbl: Use ubi_eba_atomic_leb

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Message-ID: <54536B22.4000807@nod.at>
Date:	Fri, 31 Oct 2014 11:57:38 +0100
From:	Richard Weinberger <richard@....at>
To:	hujianyang <hujianyang@...wei.com>
CC:	dedekind1@...il.com, dwmw2@...radead.org,
	computersforpeace@...il.com, linux-mtd@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] UBI: vtbl: Use ubi_eba_atomic_leb_change()

Am 31.10.2014 um 11:45 schrieb hujianyang:
> This question is basing on your comment for this patch:
> 
> """
> we can guarantee that the first VTBL record is always
> correct and we don't really need the second one anymore.
> """
> 
> I think that means one PEB is enough in your considering.
> So I want to know if you are sure about this. Because
> we use two leb for master_node in ubifs-level. So maybe
> VTBL is like super_node, not master_node, right?

Yes, technically one PEB is enough if atomic leb change is used.
But existing UBI implementations want a second one
and a backup VTBL PEB is good for robustness.
i.e. if the PEB turns bad we have a backup and do not lose
all volume meta information.

Thanks,
//richard
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