Re: [PATCH v2] null_blk: fix null-ptr-dereference while configuring 'power' and 'submit_queues'

[Markus Elfring]

…
> Fix this problem by resuing the global mutex to protect
> nullb_device_power_store() and nullb_update_nr_hw_queues() from configfs.
>
> Fixes: 45919fbfe1c4 ("null_blk: Enable modifying 'submit_queues' after an instance has been configured")
…
> +++ b/drivers/block/null_blk/main.c
> @@ -413,13 +413,25 @@ static int nullb_update_nr_hw_queues(struct nullb_device *dev,
>  static int nullb_apply_submit_queues(struct nullb_device *dev,
>  				     unsigned int submit_queues)
>  {
> -	return nullb_update_nr_hw_queues(dev, submit_queues, dev->poll_queues);
> +	int ret;
> +
> +	mutex_lock(&lock);
> +	ret = nullb_update_nr_hw_queues(dev, submit_queues, dev->poll_queues);
> +	mutex_unlock(&lock);
> +
> +	return ret;
>  }
…

How do you think about to increase the application of scope-based resource management here?
https://elixir.bootlin.com/linux/v6.9.1/source/include/linux/cleanup.h#L124

Will development interests grow for the usage of a statement like “guard(mutex)(&lock);”?

Regards,
Markus