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

On 10/19/2016 06:23 AM, Christoph Hellwig wrote:

quoted

+/**
+ * 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.

quoted

+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.

quoted

+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.