Re: [PATCH V2 RESEND 3/5] blk-mq: stop to handle IO before hctx's all CPUs become offline

[John Garry <john.garry@huawei.com>]

On 06/10/2019 03:45, Ming Lei wrote:
> +	}
> +}
> +
> +static int blk_mq_hctx_notify_online(unsigned int cpu, struct hlist_node *node)
> +{
> +	struct blk_mq_hw_ctx *hctx = hlist_entry_safe(node,
> +			struct blk_mq_hw_ctx, cpuhp_online);
> +	unsigned prev_cpu = -1;
> +
> +	while (true) {
> +		unsigned next_cpu = cpumask_next_and(prev_cpu, hctx->cpumask,
> +				cpu_online_mask);
> +
> +		if (next_cpu >= nr_cpu_ids)
> +			break;
> +
> +		/* return if there is other online CPU on this hctx */
> +		if (next_cpu != cpu)
> +			return 0;
> +
> +		prev_cpu = next_cpu;
> +	}
> +
> +	set_bit(BLK_MQ_S_INTERNAL_STOPPED, &hctx->state);
> +	blk_mq_drain_inflight_rqs(hctx);
> +

Does this do the same:

{
	struct blk_mq_hw_ctx *hctx = hlist_entry_safe(node,
			struct blk_mq_hw_ctx, cpuhp_online);
	cpumask_var_t tmp;

	cpumask_and(tmp, hctx->cpumask, cpu_online_mask);

	/* test if there is any other cpu online in the hctx cpu mask */
	if (cpumask_any_but(tmp, cpu) < nr_cpu_ids)
		return 0;

	set_bit(BLK_MQ_S_INTERNAL_STOPPED, &hctx->state);
	blk_mq_drain_inflight_rqs(hctx);

	return 0;
}

If so, it's more readable and concise.

Thanks,
John


BTW, You could have added my Tested-by tags...

> +	return 0;
> +}
> +