linux-kernel - RE: [PATCH v3 1/1] mtd: spi-nor: core: Prevent oops during driver removal with active read or write operations

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Message-ID:
 <MN2PR03MB4927D29E06586CCE7D0547FEC632A@MN2PR03MB4927.namprd03.prod.outlook.com>
Date: Thu, 21 Aug 2025 00:32:45 +0000
From: "Romli, Khairul Anuar" <khairul.anuar.romli@...era.com>
To: Michael Walle <mwalle@...nel.org>, Tudor Ambarus
	<tudor.ambarus@...aro.org>, Pratyush Yadav <pratyush@...nel.org>, Miquel
 Raynal <miquel.raynal@...tlin.com>, Richard Weinberger <richard@....at>,
	Vignesh Raghavendra <vigneshr@...com>, "open list:SPI NOR SUBSYSTEM"
	<linux-mtd@...ts.infradead.org>, open list <linux-kernel@...r.kernel.org>,
	"Gerlach, Matthew" <matthew.gerlach@...era.com>
Subject: RE: [PATCH v3 1/1] mtd: spi-nor: core: Prevent oops during driver
 removal with active read or write operations

Hi Michael,

Sorry for taking very long time to reply. Could you advise me what kind of analysis do you want me to provide?

Thanks.

Regards,
Khairul

> -----Original Message-----
> From: Michael Walle <mwalle@...nel.org>
> Sent: Wednesday, 30 July, 2025 3:50 PM
> To: Romli, Khairul Anuar <khairul.anuar.romli@...era.com>; Tudor Ambarus
> <tudor.ambarus@...aro.org>; Pratyush Yadav <pratyush@...nel.org>; Miquel
> Raynal <miquel.raynal@...tlin.com>; Richard Weinberger <richard@....at>;
> Vignesh Raghavendra <vigneshr@...com>; open list:SPI NOR SUBSYSTEM
> <linux-mtd@...ts.infradead.org>; open list <linux-kernel@...r.kernel.org>;
> Gerlach, Matthew <matthew.gerlach@...era.com>
> Subject: Re: [PATCH v3 1/1] mtd: spi-nor: core: Prevent oops during driver
> removal with active read or write operations
> 
> Hi,
> 
> > > On Wed Jul 30, 2025 at 3:39 AM CEST, Khairul Anuar Romli wrote:
> > > > From: kromli <khairul.anuar.romli@...era.com>
> > > >
> > > > Ensure that the pointer passed to module_put() in
> > > > spi_nor_put_device() is not NULL before use. This change adds a
> > > > guard clause to return early, preventing the kernel crash below
> > > > when the cadence-qspi driver is removed during a dd operation:
> > >
> > > As already asked in v2. This needs a (more detailed) description
> > > what is going on and what is going wrong.
> > >
> > > -michael
> >
> > Hi,
> >
> > We just run the following test we observe the crash.
> >
> > time dd if=/dev/mtd1 of=out.img bs=1MB count=1000 & echo spi0.0 >
> > /sys/bus/spi/drivers/spi-nor/unbind
> > echo spi0.0 > /sys/bus/spi/drivers/spi-nor/bind
> >
> > From the observation, the dd is not entirely terminated when the unbind
> took place.
> > Maybe there is other changes require to ensure the dd operation gets
> > terminated when driver unbind/remove.
> 
> I'd expect an analysis what's going wrong in the kernel to judge the correctness
> of the patch.
> 
> Thanks,
> -michael