Re: [RFC PATCH 3/7] blk-mq: stop to handle IO before hctx's all CPUs become offline

From: Minwoo Im <minwoo.im.dev@gmail.com>
To: Ming Lei <ming.lei@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>,
	linux-block@vger.kernel.org,
	"James E . J . Bottomley" <jejb@linux.ibm.com>,
	"Martin K . Petersen" <martin.petersen@oracle.com>,
	linux-scsi@vger.kernel.org, Bart Van Assche <bvanassche@acm.org>,
	Hannes Reinecke <hare@suse.com>, Christoph Hellwig <hch@lst.de>,
	Thomas Gleixner <tglx@linutronix.de>,
	Keith Busch <keith.busch@intel.com>,
	Minwoo Im <minwoo.im.dev@gmail.com>
Subject: Re: [RFC PATCH 3/7] blk-mq: stop to handle IO before hctx's all CPUs become offline
Date: Fri, 12 Jul 2019 18:03:50 +0900	[thread overview]
Message-ID: <20190712090350.GB31048@minwoo-desktop> (raw)
In-Reply-To: <20190712024726.1227-4-ming.lei@redhat.com>

On 19-07-12 10:47:22, Ming Lei wrote:
> diff --git a/block/blk-mq.c b/block/blk-mq.c
> index e5ef40c603ca..028c5d78e409 100644
> --- a/block/blk-mq.c
> +++ b/block/blk-mq.c
> @@ -2205,6 +2205,64 @@ int blk_mq_alloc_rqs(struct blk_mq_tag_set *set, struct blk_mq_tags *tags,
>  	return -ENOMEM;
>  }
>  
> +static bool blk_mq_count_inflight_rq(struct request *rq, void *data,
> +				     bool reserved)
> +{
> +	unsigned *count = data;
> +
> +	if ((blk_mq_rq_state(rq) == MQ_RQ_IN_FLIGHT))
> +		(*count)++;
> +
> +	return true;
> +}
> +
> +unsigned blk_mq_tags_inflight_rqs(struct blk_mq_tags *tags)
> +{
> +	unsigned count = 0;
> +
> +	blk_mq_all_tag_busy_iter(tags, blk_mq_count_inflight_rq, &count);
> +
> +	return count;
> +}

Ming,

Maybe it can be static?

> +
> +static void blk_mq_drain_inflight_rqs(struct blk_mq_hw_ctx *hctx)
> +{
> +	while (1) {
> +		if (!blk_mq_tags_inflight_rqs(hctx->tags))
> +			break;
> +		msleep(5);
> +	}
> +}