Re: [PATCH v5 01/58] mtd: nand: denali: add missing nand_release() call in denali_remove()

[Dinh Nguyen]

Hi Boris,

On Fri, Dec 11, 2015 at 9:10 AM, Boris Brezillon
 wrote:
> + Dinh (who made commit 2a0a288ec258)
>
> Also added back the Fixes tag.
>
> On Fri, 11 Dec 2015 15:02:34 +0100
> Boris Brezillon  wrote:
>
>> Unregister the NAND device from the NAND subsystem when removing a denali
>> NAND controller, otherwise the MTD attached to the NAND device is still
>> exposed by the MTD layer, and accesses to this device will likely crash
>> the system.
>>
>> Signed-off-by: Boris Brezillon 
>
> Fixes: 2a0a288ec258 ("mtd: denali: split the generic driver and PCI layer")
>
>> ---
>> Changes since v4:
>> - remove Cc stable and fixes tags
>> - calculate the dma buffer size before calling nand_release()
>>
>>  drivers/mtd/nand/denali.c | 6 --
>>  1 file changed, 4 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/mtd/nand/denali.c b/drivers/mtd/nand/denali.c
>> index 67eb2be..fdfea05 100644
>> --- a/drivers/mtd/nand/denali.c
>> +++ b/drivers/mtd/nand/denali.c
>> @@ -1622,9 +1622,11 @@ EXPORT_SYMBOL(denali_init);
>>  /* driver exit point */
>>  void denali_remove(struct denali_nand_info *denali)
>>  {
>> + int bufsize = denali->mtd.writesize + denali->mtd.oobsize;
>> +
>> + nand_release(>mtd);
>>   denali_irq_cleanup(denali->irq, denali);
>> - dma_unmap_single(denali->dev, denali->buf.dma_buf,
>> -  denali->mtd.writesize + denali->mtd.oobsize,
>> + dma_unmap_single(denali->dev, denali->buf.dma_buf, bufsize,
>>DMA_BIDIRECTIONAL);

Not sure what is the need to add bufsize here, but the commit message
doesn't reflect the change.

Dinh
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Re: [PATCH v5 01/58] mtd: nand: denali: add missing nand_release() call in denali_remove()

[Boris Brezillon]

Hi Dinh,

On Fri, 11 Dec 2015 10:50:21 -0600
Dinh Nguyen  wrote:

> Hi Boris,
> 
> On Fri, Dec 11, 2015 at 9:10 AM, Boris Brezillon
>  wrote:
> > + Dinh (who made commit 2a0a288ec258)
> >
> > Also added back the Fixes tag.
> >
> > On Fri, 11 Dec 2015 15:02:34 +0100
> > Boris Brezillon  wrote:
> >
> >> Unregister the NAND device from the NAND subsystem when removing a denali
> >> NAND controller, otherwise the MTD attached to the NAND device is still
> >> exposed by the MTD layer, and accesses to this device will likely crash
> >> the system.
> >>
> >> Signed-off-by: Boris Brezillon 
> >
> > Fixes: 2a0a288ec258 ("mtd: denali: split the generic driver and PCI layer")
> >
> >> ---
> >> Changes since v4:
> >> - remove Cc stable and fixes tags
> >> - calculate the dma buffer size before calling nand_release()
> >>
> >>  drivers/mtd/nand/denali.c | 6 --
> >>  1 file changed, 4 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/drivers/mtd/nand/denali.c b/drivers/mtd/nand/denali.c
> >> index 67eb2be..fdfea05 100644
> >> --- a/drivers/mtd/nand/denali.c
> >> +++ b/drivers/mtd/nand/denali.c
> >> @@ -1622,9 +1622,11 @@ EXPORT_SYMBOL(denali_init);
> >>  /* driver exit point */
> >>  void denali_remove(struct denali_nand_info *denali)
> >>  {
> >> + int bufsize = denali->mtd.writesize + denali->mtd.oobsize;
> >> +
> >> + nand_release(>mtd);
> >>   denali_irq_cleanup(denali->irq, denali);
> >> - dma_unmap_single(denali->dev, denali->buf.dma_buf,
> >> -  denali->mtd.writesize + denali->mtd.oobsize,
> >> + dma_unmap_single(denali->dev, denali->buf.dma_buf, bufsize,
> >>DMA_BIDIRECTIONAL);
> 
> Not sure what is the need to add bufsize here, but the commit message
> doesn't reflect the change.

You were not in Cc of the first version (my fault), but Brian pointed
that the mtd fields could be in an unknown state after the
nand_release() call (this is currently not the case, but it change in
the future). The idea is to pre-compute the DMA buffer size before
releasing the mtd/nand device to prevent any future issues.

I don't think it is worth mentioning this in the commit message,
because these are just implementation details, but I can add the
following comment before the bufsize declaration:

/*
 * Pre-compute DMA buffer size to avoid any problems in case
 * nand_release() ever changes in a way that mtd->writesize and
 * mtd->oobsize are not reliable after this call.
 */

What do you think?

Best Regards,

Boris

> 
> Dinh



-- 
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Embedded Linux and Kernel engineering
http://free-electrons.com
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Re: [PATCH v5 01/58] mtd: nand: denali: add missing nand_release() call in denali_remove()

[Boris Brezillon]

+ Dinh (who made commit 2a0a288ec258)

Also added back the Fixes tag.

On Fri, 11 Dec 2015 15:02:34 +0100
Boris Brezillon  wrote:

> Unregister the NAND device from the NAND subsystem when removing a denali
> NAND controller, otherwise the MTD attached to the NAND device is still
> exposed by the MTD layer, and accesses to this device will likely crash
> the system.
> 
> Signed-off-by: Boris Brezillon 

Fixes: 2a0a288ec258 ("mtd: denali: split the generic driver and PCI layer")

> ---
> Changes since v4:
> - remove Cc stable and fixes tags
> - calculate the dma buffer size before calling nand_release()
> 
>  drivers/mtd/nand/denali.c | 6 --
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/mtd/nand/denali.c b/drivers/mtd/nand/denali.c
> index 67eb2be..fdfea05 100644
> --- a/drivers/mtd/nand/denali.c
> +++ b/drivers/mtd/nand/denali.c
> @@ -1622,9 +1622,11 @@ EXPORT_SYMBOL(denali_init);
>  /* driver exit point */
>  void denali_remove(struct denali_nand_info *denali)
>  {
> + int bufsize = denali->mtd.writesize + denali->mtd.oobsize;
> +
> + nand_release(>mtd);
>   denali_irq_cleanup(denali->irq, denali);
> - dma_unmap_single(denali->dev, denali->buf.dma_buf,
> -  denali->mtd.writesize + denali->mtd.oobsize,
> + dma_unmap_single(denali->dev, denali->buf.dma_buf, bufsize,
>DMA_BIDIRECTIONAL);
>  }
>  EXPORT_SYMBOL(denali_remove);



-- 
Boris Brezillon, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com
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Re: [PATCH v5 01/58] mtd: nand: denali: add missing nand_release() call in denali_remove()

[Dinh Nguyen]

On Fri, Dec 11, 2015 at 11:08 AM, Boris Brezillon
 wrote:
> Hi Dinh,
>
> On Fri, 11 Dec 2015 10:50:21 -0600
> Dinh Nguyen  wrote:
>
>> Hi Boris,
>>
>> On Fri, Dec 11, 2015 at 9:10 AM, Boris Brezillon
>>  wrote:
>> > + Dinh (who made commit 2a0a288ec258)
>> >
>> > Also added back the Fixes tag.
>> >
>> > On Fri, 11 Dec 2015 15:02:34 +0100
>> > Boris Brezillon  wrote:
>> >
>> >> Unregister the NAND device from the NAND subsystem when removing a denali
>> >> NAND controller, otherwise the MTD attached to the NAND device is still
>> >> exposed by the MTD layer, and accesses to this device will likely crash
>> >> the system.
>> >>
>> >> Signed-off-by: Boris Brezillon 
>> >
>> > Fixes: 2a0a288ec258 ("mtd: denali: split the generic driver and PCI layer")
>> >
>> >> ---
>> >> Changes since v4:
>> >> - remove Cc stable and fixes tags
>> >> - calculate the dma buffer size before calling nand_release()
>> >>
>> >>  drivers/mtd/nand/denali.c | 6 --
>> >>  1 file changed, 4 insertions(+), 2 deletions(-)
>> >>
>> >> diff --git a/drivers/mtd/nand/denali.c b/drivers/mtd/nand/denali.c
>> >> index 67eb2be..fdfea05 100644
>> >> --- a/drivers/mtd/nand/denali.c
>> >> +++ b/drivers/mtd/nand/denali.c
>> >> @@ -1622,9 +1622,11 @@ EXPORT_SYMBOL(denali_init);
>> >>  /* driver exit point */
>> >>  void denali_remove(struct denali_nand_info *denali)
>> >>  {
>> >> + int bufsize = denali->mtd.writesize + denali->mtd.oobsize;
>> >> +
>> >> + nand_release(>mtd);
>> >>   denali_irq_cleanup(denali->irq, denali);
>> >> - dma_unmap_single(denali->dev, denali->buf.dma_buf,
>> >> -  denali->mtd.writesize + denali->mtd.oobsize,
>> >> + dma_unmap_single(denali->dev, denali->buf.dma_buf, bufsize,
>> >>DMA_BIDIRECTIONAL);
>>
>> Not sure what is the need to add bufsize here, but the commit message
>> doesn't reflect the change.
>
> You were not in Cc of the first version (my fault), but Brian pointed
> that the mtd fields could be in an unknown state after the
> nand_release() call (this is currently not the case, but it change in
> the future). The idea is to pre-compute the DMA buffer size before
> releasing the mtd/nand device to prevent any future issues.
>
> I don't think it is worth mentioning this in the commit message,
> because these are just implementation details, but I can add the
> following comment before the bufsize declaration:
>
> /*
>  * Pre-compute DMA buffer size to avoid any problems in case
>  * nand_release() ever changes in a way that mtd->writesize and
>  * mtd->oobsize are not reliable after this call.
>  */
>
> What do you think?
>

Ah, perfect! With the updated comment,

Acked-by: Dinh Nguyen 

Thanks,
Dinh
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