Re: [PATCH] mtd: partitions: Handle add_mtd_device() failures gracefully

From: Geert Uytterhoeven <geert@linux-m68k.org>
To: Boris Brezillon <boris.brezillon@bootlin.com>
Cc: Marek Vasut <marek.vasut@gmail.com>,
	Boris Brezillon <boris.brezillon@free-electrons.com>,
	Geert Uytterhoeven <geert+renesas@glider.be>,
	Richard Weinberger <richard@nod.at>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Linux-Renesas <linux-renesas-soc@vger.kernel.org>,
	MTD Maling List <linux-mtd@lists.infradead.org>,
	Brian Norris <computersforpeace@gmail.com>,
	David Woodhouse <dwmw2@infradead.org>
Subject: Re: [PATCH] mtd: partitions: Handle add_mtd_device() failures gracefully
Date: Thu, 26 Apr 2018 19:56:58 +0200	[thread overview]
Message-ID: <CAMuHMdWRyZYX+oKN-nxzKbCqZn1zojKwX8Gv6tGg=UZSa3k_LA@mail.gmail.com> (raw)
In-Reply-To: <20180426195303.1f08d2cd@bbrezillon>

Hi Boris,

On Thu, Apr 26, 2018 at 7:53 PM, Boris Brezillon
<boris.brezillon@bootlin.com> wrote:
> On Tue, 10 Apr 2018 15:26:20 +0200
> Geert Uytterhoeven <geert@linux-m68k.org> wrote:
>> On Mon, Apr 9, 2018 at 11:59 PM, Marek Vasut <marek.vasut@gmail.com> wrote:
>> > On 04/09/2018 02:25 PM, Geert Uytterhoeven wrote:
>> >> Currently add_mtd_device() failures are plainly ignored, which may lead
>> >> to kernel crashes later.
>>
>> >> Fix this by ignoring and freeing partitions that failed to add in
>> >> add_mtd_partitions().  The same issue is present in mtd_add_partition(),
>> >> so fix that as well.
>> >>
>> >> Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
>> >> ---
>> >> I don't know if it is worthwhile factoring out the common handling.
>> >>
>> >> Should allocate_partition() fail instead?  There's a comment saying
>> >> "let's register it anyway to preserve ordering".
>>
>> >> --- a/drivers/mtd/mtdpart.c
>> >> +++ b/drivers/mtd/mtdpart.c
>>
>> >> @@ -746,7 +753,15 @@ int add_mtd_partitions(struct mtd_info *master,
>> >>               list_add(&slave->list, &mtd_partitions);
>> >>               mutex_unlock(&mtd_partitions_mutex);
>> >>
>> >> -             add_mtd_device(&slave->mtd);
>> >> +             ret = add_mtd_device(&slave->mtd);
>> >> +             if (ret) {
>> >> +                     mutex_lock(&mtd_partitions_mutex);
>> >> +                     list_del(&slave->list);
>> >> +                     mutex_unlock(&mtd_partitions_mutex);
>> >> +                     free_partition(slave);
>> >> +                     continue;
>> >> +             }
>> >
>> > Why is the partition even in the list in the first place ? Can we avoid
>> > adding it rather than adding and removing it ?
>>
>> Hence my question "Should allocate_partition() fail instead?".
>
> I'd prefer this option too. Can you prepare a new version doing that?

OK, then I have another question ;-)

Should this be a special failure, so all other valid partitions on the
same FLASH
are still added, or should it be fatal, so no partitions are added at all?

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds