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From:   Richard Weinberger <richard@nod.at>
To:     Boris Brezillon <boris.brezillon@bootlin.com>
Cc:     Ben Hutchings <ben.hutchings@codethink.co.uk>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        linux-kernel@vger.kernel.org, stable@vger.kernel.org,
        Sascha Hauer <s.hauer@pengutronix.de>,
        Boris Brezillon <boris.brezillon@free-electrons.com>,
        Sasha Levin <alexander.levin@microsoft.com>
Subject: Re: [PATCH 4.4 03/34] mtd: nand: gpmi: Fix failure when a erased page has a bitflip at BBM
Date:   Wed, 07 Mar 2018 09:19:15 +0100
Message-ID: <3306133.ouE1UNrexX@blindfold>
In-Reply-To: <20180307091236.741b7fd2@bbrezillon>
References: <20180302084435.842679610@linuxfoundation.org> <1520371350.23626.23.camel@codethink.co.uk> <20180307091236.741b7fd2@bbrezillon>
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Boris,

Am Mittwoch, 7. M?rz 2018, 09:12:36 CET schrieb Boris Brezillon:
> On Tue, 06 Mar 2018 21:22:30 +0000
> 
> Ben Hutchings <ben.hutchings@codethink.co.uk> wrote:
> > On Fri, 2018-03-02 at 09:50 +0100, Greg Kroah-Hartman wrote:
> > > 4.4-stable review patch.  If anyone has any objections, please let me
> > > know.
> > > 
> > > ------------------
> > > 
> > > From: Sascha Hauer <s.hauer@pengutronix.de>
> > > 
> > > 
> > > [ Upstream commit fdf2e821052958a114618a95ab18a300d0b080cb ]
> > > 
> > > When erased subpages are read then the BCH decoder returns STATUS_ERASED
> > > if they are all empty, or STATUS_UNCORRECTABLE if there are bitflips.
> > > When there are bitflips, we have to set these bits again to show the
> > > upper layers a completely erased page. When a bitflip happens in the
> > > exact byte where the bad block marker is, then this byte is swapped
> > > with another byte in block_mark_swapping(). The correction code then
> > > detects a bitflip in another subpage and no longer corrects the bitflip
> > > where it really happens.
> > 
> > [...]
> > 
> > This seesm to be a bug fix for commit bd2e778c9ee3 "gpmi-nand: Handle
> > ECC Errors in erased pages".  That's not in 4.4 so the bug fix is not
> > needed, though it doesn't appear to do any harm.
> 
> I wonder why the fix was backported to stable releases in the first
> place. AFAICS, there's no Cc-stable or Fixes tag in the original
> commit. It's probably something in the backport-to-stable process I'm
> not aware of.

It was auto selected by a stable script.

Thanks,
//richard