linux-kernel - Re: [PATCH 4.4 15/47] ubi: fastmap: Correctly handle interrupted erasures in EBA

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Message-ID: <1532571174.21552.47.camel@codethink.co.uk>
Date:   Thu, 26 Jul 2018 10:12:54 +0800
From:   Ben Hutchings <ben.hutchings@...ethink.co.uk>
To:     martin bayern <Martinbayern@...look.com>,
        Richard Weinberger <richard@....at>
Cc:     stable@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 4.4 15/47] ubi: fastmap: Correctly handle interrupted
 erasures in EBA

On Tue, 2018-07-10 at 20:24 +0200, Greg Kroah-Hartman wrote:
> 4.4-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.
[...]

Isn't there a risk here, that a read error leads to erasing data that
might be recoverable if the read is retried?

Ben.

-- 
Ben Hutchings, Software Developer                         Codethink Ltd
https://www.codethink.co.uk/                 Dale House, 35 Dale Street
                                     Manchester, M1 2HF, United Kingdom