linux-kernel - Re: [PATCH v3] mtd: Verify written data in paranoid mode

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Message-ID: <87y0v1g7xz.fsf@bootlin.com>
Date: Mon, 12 May 2025 17:33:28 +0200
From: Miquel Raynal <miquel.raynal@...tlin.com>
To: Richard Weinberger <richard@....at>
Cc: Csókás Bence <csokas.bence@...lan.hu>,  linux-mtd
 <linux-mtd@...ts.infradead.org>,  linux-kernel
 <linux-kernel@...r.kernel.org>,  Vignesh Raghavendra <vigneshr@...com>
Subject: Re: [PATCH v3] mtd: Verify written data in paranoid mode

On 12/05/2025 at 17:23:16 +02, Richard Weinberger <richard@....at> wrote:

> ----- Ursprüngliche Mail -----
>> Von: "Miquel Raynal" <miquel.raynal@...tlin.com>
>>> The problem we _have_ though happens to be a bit different: here we are
>>> blursed with a system that corrupts data at a noticeable
>>> probability. But the model is the same: a stochastic process introducing
>>> bit errors on write. But I sincerely hope no one else has this problem,
>>> and this is *not* the primary aim of this patch; it just happens to
>>> solve our issue as well. But I intend it to be useful for the larger
>>> Linux community, thus the primary goal is to solve the first issue.
>> 
>> I don't have a strong opinion there but I don't dislike this idea
>> because it might also help troubleshooting errors sometimes. It is very
>> hard to understand issues which happen to be discovered way after they
>> have been generated (typically during a read, way later than a "faulty"
>> write). Having this paranoid option would give a more synchronous
>> approach which is easier to work with sometimes.
>
> UBI offers this already, there is a write self-check as part of the io
> checks that can be enabled
> via debugfs per UBI device.
> So for troubleshooting this should be good enough.
> There is room for improvement, though. Currently it uses vmalloc().

UBI is full of uncovered resources :-)