linux-kernel - Re: [PATCH] spi-nor: Verify written data in paranoid mode

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Message-ID: <81225127.297167214.1744828878236.JavaMail.zimbra@nod.at>
Date: Wed, 16 Apr 2025 20:41:18 +0200 (CEST)
From: Richard Weinberger <richard@....at>
To: Csókás Bence <csokas.bence@...lan.hu>
Cc: Michael Walle <mwalle@...nel.org>, linux-mtd <linux-mtd@...ts.infradead.org>, 
	linux-kernel <linux-kernel@...r.kernel.org>, 
	Tamás Szentendrei <szentendrei.tamas@...lan.hu>, 
	Tudor Ambarus <tudor.ambarus@...aro.org>, 
	pratyush <pratyush@...nel.org>, 
	Miquel Raynal <miquel.raynal@...tlin.com>, 
	Vignesh Raghavendra <vigneshr@...com>
Subject: Re: [PATCH] spi-nor: Verify written data in paranoid mode

----- Ursprüngliche Mail -----
> Von: "Csókás Bence" <csokas.bence@...lan.hu>
>> I'm not so sure whether it makes sense at all.
>> In it's current form, there is no recovery. So anything non-trivial
>> on top of the MTD will just see an -EIO and has to give up.
>> E.g. a filesystem will remount read-only.
> 
> In our case, we use UBIFS on top of UBI, which in this case chooses
> another eraseblock to hold the data instead, then re-tests (erase+write
> cycles) the one which gave -EIO. Since the bus error is only transient,
> it goes away by this time, and thus UBIFS will recover from this cleanly.

Are you sure about that?

I'd expect UBI to go into RO mode via a call path like:
ubi_eba_write_leb() -> ubi_io_write() -> mtd_write()
If mtd_write() returns an EIO, UBI will go into RO mode immediately.

(I'm assuming, your SPI-NOR has no bad block support, so ubi->bad_allowed
is false).

Thanks,
//richard