linux-kernel - Re: [PATCH 4.9 069/101] ubi: fastmap: Correctly handle interrupted erasures in EBA

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Date:   Sun, 23 Sep 2018 14:49:23 +0200
From:   Lars Persson <lists@...h.nu>
To:     gregkh@...uxfoundation.org
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Martinbayern@...look.com, richard@....at
Subject: Re: [PATCH 4.9 069/101] ubi: fastmap: Correctly handle interrupted
 erasures in EBA

On Sun, Jul 1, 2018 at 6:27 PM Greg Kroah-Hartman
<gregkh@...uxfoundation.org> wrote:
>
> 4.9-stable review patch.  If anyone has any objections, please let me know.
>
> ------------------
>
> From: Richard Weinberger <richard@....at>
>
> commit 781932375ffc6411713ee0926ccae8596ed0261c upstream.
>
> Fastmap cannot track the LEB unmap operation, therefore it can
> happen that after an interrupted erasure the mapping still looks
> good from Fastmap's point of view, while reading from the PEB will
> cause an ECC error and confuses the upper layer.
>
> Instead of teaching users of UBI how to deal with that, we read back
> the VID header and check for errors. If the PEB is empty or shows ECC
> errors we fixup the mapping and schedule the PEB for erasure.
>
> Fixes: dbb7d2a88d2a ("UBI: Add fastmap core")
> Cc: <stable@...r.kernel.org>
> Reported-by: martin bayern <Martinbayern@...look.com>
> Signed-off-by: Richard Weinberger <richard@....at>
> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
>
>
Hi Greg

This commit belongs to a series of 3 commits that are intended to be
used together. Currently the stable branches have only the first
commit from the series and we get a UBI speed regression because an
extra NAND page read is always performed for each access to a UBI LEB.

3e5e4335cc0ffd668054564b113fb3c9c97badb8 ubi: fastmap: Detect EBA
mismatches on-the-fly
34653fd8c46e771585fce5975e4243f8fd401914 ubi: fastmap: Check each
mapping only once
781932375ffc6411713ee0926ccae8596ed0261c ubi: fastmap: Correctly
handle interrupted erasures in EBA

This will in turn require also this follow-up patch:
25677478474a91fa1b46f19a4a591a9848bca6fb ubi: Initialize Fastmap
checkmapping correctly


BR,
 Lars Persson