> +/*
> + * Find and return io_wq with given id and grab a reference to it.
> + */
> +struct io_wq *io_wq_create_id(unsigned bounded, struct io_wq_data *data,
> +			      unsigned int id)
> +{
> +	struct io_wq *wq, *ret = NULL;
> +
> +	mutex_lock(&wq_lock);
> +	list_for_each_entry(wq, &wq_list, wq_list) {
> +		if (id != wq->id)
> +			continue;
> +		if (data->creds != wq->creds || data->user != wq->user)
> +			continue;
> +		if (data->get_work != wq->get_work ||
> +		    data->put_work != wq->put_work)
> +			continue;
> +		if (!refcount_inc_not_zero(&wq->use_refs))
> +			continue;
> +		ret = wq;
> +		break;
> +	}
> +	mutex_unlock(&wq_lock);

Isn't there a more efficient ida_find function in order to avoid
the loop, which won't really scale in the long run.

metze