linux-kernel - Re: [PATCH] mtd: partitions: Handle add_mtd

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Date:   Tue, 10 Apr 2018 15:26:20 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Marek Vasut <marek.vasut@...il.com>
Cc:     Geert Uytterhoeven <geert+renesas@...der.be>,
        David Woodhouse <dwmw2@...radead.org>,
        Brian Norris <computersforpeace@...il.com>,
        Boris Brezillon <boris.brezillon@...e-electrons.com>,
        Richard Weinberger <richard@....at>,
        MTD Maling List <linux-mtd@...ts.infradead.org>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mtd: partitions: Handle add_mtd_device() failures gracefully

Hi Marek,

On Mon, Apr 9, 2018 at 11:59 PM, Marek Vasut <marek.vasut@...il.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@...der.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?".
Note that if we go that route, it should be a "soft" failure, as we
probably don't
want to drop all other partitions on the device.

>>               mtd_add_partition_attrs(slave);
>>               if (parts[i].types)
>>                       mtd_parse_part(slave, parts[i].types);
>>

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-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