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

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Date:	Fri, 11 Dec 2015 11:21:55 -0600
From:	Dinh Nguyen <dinh.linux@...il.com>
To:	Boris Brezillon <boris.brezillon@...e-electrons.com>
Cc:	David Woodhouse <dwmw2@...radead.org>,
	Brian Norris <computersforpeace@...il.com>,
	linux-mtd@...ts.infradead.org, Andrew Lunn <andrew@...n.ch>,
	Krzysztof Kozlowski <k.kozlowski@...sung.com>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
	Tony Lindgren <tony@...mide.com>,
	Nicolas Ferre <nicolas.ferre@...el.com>,
	Stefan Agner <stefan@...er.ch>, linux-sunxi@...glegroups.com,
	Alexandre Belloni <alexandre.belloni@...e-electrons.com>,
	Robert Jarzmik <robert.jarzmik@...e.fr>,
	Alexander Clouter <alex@...riz.org.uk>,
	"devel@...verdev.osuosl.org" <devel@...verdev.osuosl.org>,
	Jesper Nilsson <jesper.nilsson@...s.com>,
	linux-samsung-soc@...r.kernel.org,
	Maxim Levitsky <maximlevitsky@...il.com>,
	Jonathan Corbet <corbet@....net>,
	Marek Vasut <marek.vasut@...il.com>,
	Chen-Yu Tsai <wens@...e.org>, Kukjin Kim <kgene@...nel.org>,
	Ezequiel Garcia <ezequiel.garcia@...e-electrons.com>,
	Jean-Christophe Plagniol-Villard <plagnioj@...osoft.com>,
	Dinh Nguyen <dinguyen@...era.com>,
	Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>,
	Jason Cooper <jason@...edaemon.net>,
	Wan ZongShun <mcuos.com@...il.com>,
	Steven Miao <realmz6@...il.com>,
	Haojian Zhuang <haojian.zhuang@...il.com>,
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	Krzysztof Halasa <khalasa@...p.pl>,
	Gregory CLEMENT <gregory.clement@...e-electrons.com>,
	linux-omap@...r.kernel.org,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
	Ryan Mallon <rmallon@...il.com>, linux-cris-kernel@...s.com,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
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	Sascha Hauer <kernel@...gutronix.de>,
	Maxime Ripard <maxime.ripard@...e-electrons.com>,
	Imre Kaloz <kaloz@...nwrt.org>,
	Shawn Guo <shawnguo@...nel.org>,
	Daniel Mack <daniel@...que.org>
Subject: Re: [PATCH v5 01/58] mtd: nand: denali: add missing nand_release()
 call in denali_remove()

On Fri, Dec 11, 2015 at 11:08 AM, Boris Brezillon
<boris.brezillon@...e-electrons.com> wrote:
> Hi Dinh,
>
> On Fri, 11 Dec 2015 10:50:21 -0600
> Dinh Nguyen <dinh.linux@...il.com> wrote:
>
>> Hi Boris,
>>
>> On Fri, Dec 11, 2015 at 9:10 AM, Boris Brezillon
>> <boris.brezillon@...e-electrons.com> wrote:
>> > + Dinh (who made commit 2a0a288ec258)
>> >
>> > Also added back the Fixes tag.
>> >
>> > On Fri, 11 Dec 2015 15:02:34 +0100
>> > Boris Brezillon <boris.brezillon@...e-electrons.com> 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 <boris.brezillon@...e-electrons.com>
>> >
>> > 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(&denali->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 <dinguyen@...nsource.altera.com>

Thanks,
Dinh
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