linux-kernel - Re: [PATCH 0/9] drivers:mtd:UBI: add bakvol module for MLC NAND paired page issue

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Message-ID: <20150930093355.3266a4b3@bbrezillon>
Date:	Wed, 30 Sep 2015 09:33:55 +0200
From:	Boris Brezillon <boris.brezillon@...e-electrons.com>
To:	"Bean Huo 霍斌斌 (beanhuo)" <beanhuo@...ron.com>
Cc:	Richard Weinberger <richard@....at>,
	"dedekind1@...il.com" <dedekind1@...il.com>,
	"adrian.hunter@...el.com" <adrian.hunter@...el.com>,
	"computersforpeace@...il.com" <computersforpeace@...il.com>,
	"baruch@...s.co.il" <baruch@...s.co.il>,
	"asierra@...-inc.com" <asierra@...-inc.com>,
	"guz.fnst@...fujitsu.com" <guz.fnst@...fujitsu.com>,
	"gsi@...x.de" <gsi@...x.de>, David Woodhouse <dwmw2@...radead.org>,
	"linux-mtd@...ts.infradead.org" <linux-mtd@...ts.infradead.org>,
	"Frank Liu 刘群 (frankliu)" <frankliu@...ron.com>,
	Andrea Scian <rnd4@...e-tech.it>,
	"Karl Zhang 张双锣 (karlzhang)" 
	<karlzhang@...ron.com>,
	Iwo Mergler <Iwo.Mergler@...commwireless.com>,
	"Jeff Lauruhn (jlauruhn)" <jlauruhn@...ron.com>,
	Stefan Roese <sr@...x.de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 0/9] drivers:mtd:UBI: add bakvol module for MLC NAND
 paired page issue

On Wed, 30 Sep 2015 05:31:43 +0000
Bean Huo 霍斌斌 (beanhuo) <beanhuo@...ron.com> wrote:

> > Am 28.09.2015 um 09:02 schrieb Bean Huo 霍斌斌 (beanhuo):
> > > Hello,
> > >
> > > This series aims at adding a bakvol module for MLC NAND paired page
> > > Power loss protection.
> > > MLC NAND paired page power loss is a known issue so far, MLC NAND
> > > pages are coupled in a sense that if you cut power while writing to a
> > > page, you corrupt not only this page, but also one of the previous pages
> > which is paired with the current one.
> > > Currently, there is no a perfect solution for this.
> > > This paired page solution is based on NAND multiple plane program
> > > feature. For this Patch, only used dual plane page program, means two
> > > different plane pages can Be programmed together at the same time.
> > > Dual plane page program only implements in backup operation. Only
> > > lower page data Be duplicated and back up into a internal log volume by
> > dual plane program method.
> > >
> > > This patch has been testing on Micron 70s/80s/90s MLC NAND.
> > > Of course there are some places needed to be improved and simplified.
> > >
> > > Any suggestion and comments welcomed.
> > 
> > As stated before, using OOB in UBI is not going to happen unless proven that
> > there is absolutely no other way to solve the paired pages problem.
> > 
> > Nacked-by: Richard Weinberger <richard@....at>
> > 
> > Sorry,
> > //Richard
> 
> Hi, Richard
> Thanks for your concern. I am a new patch submitter.
> Can you tell me Nacked-by means?
> 
> By the way, Do you review my patches series ? I don't backup duplicated data in OOB .

That's not what Richard said, he just pointed that you were using the
OOB area, and you're actually using it to store the information about
which page you're backuping.

> Can you specify which sector codes ? so that I can explain it in detail.

And as answered by Richard, check_original_data() and
mtd_write_dual_plane_oob() are filling the OOB buf with the original
page offset, so you're definitely using the OOB area to store metadata.

-- 
Boris Brezillon, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com
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