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

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Message-ID: <20180426200923.4a13474e@bbrezillon>
Date:   Thu, 26 Apr 2018 20:09:23 +0200
From:   Boris Brezillon <boris.brezillon@...tlin.com>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Marek Vasut <marek.vasut@...il.com>,
        Boris Brezillon <boris.brezillon@...e-electrons.com>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Richard Weinberger <richard@....at>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>,
        MTD Maling List <linux-mtd@...ts.infradead.org>,
        Brian Norris <computersforpeace@...il.com>,
        David Woodhouse <dwmw2@...radead.org>
Subject: Re: [PATCH] mtd: partitions: Handle add_mtd_device() failures
 gracefully

On Thu, 26 Apr 2018 19:56:58 +0200
Geert Uytterhoeven <geert@...ux-m68k.org> wrote:

> Hi Boris,
> 
> On Thu, Apr 26, 2018 at 7:53 PM, Boris Brezillon
> <boris.brezillon@...tlin.com> wrote:
> > On Tue, 10 Apr 2018 15:26:20 +0200
> > Geert Uytterhoeven <geert@...ux-m68k.org> 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?".  
> >
> > 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?

I guess we can go for the "drop the invalid partitions and print a
warning" approach. Anyway, I'm sure people will notice really quickly
when one of their partition is missing, so it's not a big deal IMO.