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

[Romli, Khairul Anuar]

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@xxxxxxxxxx>
> Sent: Wednesday, 30 July, 2025 3:50 PM
> To: Romli, Khairul Anuar <khairul.anuar.romli@xxxxxxxxxx>; Tudor Ambarus
> <tudor.ambarus@xxxxxxxxxx>; Pratyush Yadav <pratyush@xxxxxxxxxx>; Miquel
> Raynal <miquel.raynal@xxxxxxxxxxx>; Richard Weinberger <richard@xxxxxx>;
> Vignesh Raghavendra <vigneshr@xxxxxx>; open list:SPI NOR SUBSYSTEM
> <linux-mtd@xxxxxxxxxxxxxxxxxxx>; open list <linux-kernel@xxxxxxxxxxxxxxx>;
> Gerlach, Matthew <matthew.gerlach@xxxxxxxxxx>
> 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@xxxxxxxxxx>
> > > >
> > > > 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