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

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Message-ID: <CAMuHMdWm96dPSx8bms0esFaDhCri9daon0UT4x=qEqeK2XFnTA@mail.gmail.com>
Date:   Tue, 10 Apr 2018 16:47:02 +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 Tue, Apr 10, 2018 at 4:37 PM, Marek Vasut <marek.vasut@...il.com> wrote:
> On 04/10/2018 03:26 PM, Geert Uytterhoeven wrote:
>> 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.
> Is the number of partitions ie. in /proc/mtdparts an ABI ?

I don't know.

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