[PATCH 4/4] mtd: warn when registering the same master many times

[Richard Weinberger]

Am 02.06.2015 um 01:17 schrieb Brian Norris:
> When CONFIG_MTD_PARTITIONED_MASTER=y, it is fatal to call
> mtd_device_parse_register() twice on the same MTD, as we try to register
> the same device/kobject multipile times.
> 
> When CONFIG_MTD_PARTITIONED_MASTER=n, calling
> mtd_device_parse_register() is more of just a nuisance, as we can mostly
> navigate around any conflicting actions.
> 
> But anyway, doing so is a Bad Thing (TM), and we should complain loudly
> for any drivers that try to do this.
> 
> Signed-off-by: Brian Norris <computersforpeace at gmail.com>
> ---
>  drivers/mtd/mtdcore.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/drivers/mtd/mtdcore.c b/drivers/mtd/mtdcore.c
> index 03eec42dc715..f0e157e0be89 100644
> --- a/drivers/mtd/mtdcore.c
> +++ b/drivers/mtd/mtdcore.c
> @@ -387,6 +387,14 @@ int add_mtd_device(struct mtd_info *mtd)
>  	struct mtd_notifier *not;
>  	int i, error;
>  
> +	/*
> +	 * May occur, for instance, on buggy drivers which call
> +	 * mtd_device_parse_register() multiple times on the same master MTD,
> +	 * especially with CONFIG_MTD_PARTITIONED_MASTER=y.
> +	 */
> +	if (WARN(mtd->backing_dev_info, "MTD already registered\n"))
> +		return -EEXIST;
> +
>  	mtd->backing_dev_info = &mtd_bdi;
>  
>  	BUG_ON(mtd->writesize == 0);
> @@ -597,6 +605,7 @@ int mtd_device_parse_register(struct mtd_info *mtd, const char * const *types,
>  	 * does cause problems with parse_mtd_partitions() above (e.g.,
>  	 * cmdlineparts will register partitions more than once).
>  	 */
> +	WARN(mtd->reboot_notifier.notifier_call, "MTD already registered\n");
>  	if (mtd->_reboot && !mtd->reboot_notifier.notifier_call) {
>  		mtd->reboot_notifier.notifier_call = mtd_reboot_notifier;
>  		register_reboot_notifier(&mtd->reboot_notifier);

One minor nit, IMHO WARN_ONCE() would make more sense.

Beside of that:
Reviewed-by: Richard Weinberger <richard at nod.at>

Thanks,
//richard