[PATCH v3 04/11] blk-mq: Introduce blk_mq_quiesce_queue()

[Bart Van Assche]

On 10/19/2016 06:23 AM, Christoph Hellwig wrote:
>> +/**
>> + * blk_mq_quiesce_queue() - wait until all ongoing queue_rq calls have finished
>> + *
>> + * Note: this function does not prevent that the struct request end_io()
>> + * callback function is invoked. Additionally, it is not prevented that
>> + * new queue_rq() calls occur unless the queue has been stopped first.
>> + */
>> +void blk_mq_quiesce_queue(struct request_queue *q)
>
> If this is intended to be a kerneldoc comment you need to document the 'q'
> parameter.  If not you should drop the magic "/**" marker.

Good catch. I will document the 'q' parameter.

>> +static void __blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx)
>> +{
>> +	int srcu_idx;
>> +
>> +	WARN_ON(!cpumask_test_cpu(raw_smp_processor_id(), hctx->cpumask) &&
>> +		cpu_online(hctx->next_cpu));
>> +
>> +	if (!(hctx->flags & BLK_MQ_F_BLOCKING)) {
>> +		rcu_read_lock();
>> +		blk_mq_process_rq_list(hctx);
>> +		rcu_read_unlock();
>> +	} else {
>> +		srcu_idx = srcu_read_lock(&hctx->queue_rq_srcu);
>> +		blk_mq_process_rq_list(hctx);
>> +		srcu_read_unlock(&hctx->queue_rq_srcu, srcu_idx);
>> +	}
>> +}
>
> Can you document these synchronization changes in detail in the changelog?

Sure, I will do that.

>> +static void blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
>> +				      struct request *rq, blk_qc_t *cookie)
>> +{
>> +	if (blk_mq_hctx_stopped(hctx) ||
>> +	    blk_mq_direct_issue_request(rq, cookie) != 0)
>> +		blk_mq_insert_request(rq, false, true, true);
>> +}
>
> Any reason not to merge this function with blk_mq_direct_issue_request?

That sounds like a good idea to me. I will make the proposed change.

Bart.