[U-Boot] [PATCH v3 11/11] mtd: sf: Make sf_mtd.c more robust

[Jagan Teki <jagan@openedev.com>]

On 26/11/18 2:12 PM, Boris Brezillon wrote:
> Hi Jagan,
> 
> On Thu, 22 Nov 2018 09:40:56 +0100
> Boris Brezillon <boris.brezillon@bootlin.com> wrote:
> 
>>>> +       /*
>>>> +        * Setting mtd->priv to NULL is the best we can do. Thanks to that,
>>>> +        * the MTD layer can still call mtd hooks without risking a
>>>> +        * use-after-free bug. Still, things should be fixed to prevent the
>>>> +        * spi_flash object from being destroyed when del_mtd_device() fails.
>>>> +        */
>>>> +       sf_mtd_info.priv = NULL;
>>>> +       printf("Failed to unregister MTD %s and the spi_flash object is going away: you're in deep trouble!",
>>>> +              sf_mtd_info.name);
>>>
>>> Why do we need this print?
>>
>> Yes we do, just to keep the user informed that something bad happened
>> and its spi-flash is no longer usable (at least through the MTD layer).
>>
>>> can't we do the same thing in MTD core
>>> itself, so-that it can be generic for all flash objects.
>>
>> del_mtd_device() can fail, so it's the caller responsibility to decide
>> what to do when that happens. Some users will propagate the error to
>> the upper layer and maybe cancel the device removal (AFAICT,
>> driver->remove() can return an error, not sure what happens in this
>> case though). For others, like spi-flash, the device will go away, and
>> all subsequent accesses will fail.
> 
> I'm about to send a new version fixing the problem I mentioned in patch
> 3, but before doing that, I'd like to know if my answer convinced you or
> if you'd still prefer this message to go away (or be placed in
> mtdcore/mtdpart.c).


I'm thinking of having the message still in MTD by showing which 
interface it would belongs, along with the details.