[PATCH 4/7] blk-mq: allow the driver to pass in an affinity mask

[Keith Busch]

On Mon, Aug 29, 2016 at 12:53:30PM +0200, Christoph Hellwig wrote:
> +static int blk_mq_create_mq_map(struct blk_mq_tag_set *set,
> +		const struct cpumask *affinity_mask)
> +{
> +	int queue = -1, cpu = 0;
> +
> +	set->mq_map = kzalloc_node(sizeof(*set->mq_map) * nr_cpu_ids,
> +			GFP_KERNEL, set->numa_node);
> +	if (!set->mq_map)
> +		return -ENOMEM;
> +
> +	if (!affinity_mask)
> +		return 0;	/* map all cpus to queue 0 */
> +
> +	/* If cpus are offline, map them to first hctx */
> +	for_each_online_cpu(cpu) {
> +		if (cpumask_test_cpu(cpu, affinity_mask))
> +			queue++;
> +		if (queue >= 0)
> +			set->mq_map[cpu] = queue;
> +	}

This can't be right. We have a single affinity mask for the entire
set, but what I think we want is an one affinity mask for each
nr_io_queues. The irq_create_affinity_mask should then create an array
of cpumasks based on nr_vecs..