blk-mq: factor out a blk_mq_complete_need_ipi helper

Add a helper to decide if we can complete locally or need an IPI.
Reviewed-by: Daniel Wagner <dwagner@suse.de>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block/blk-mq.c

@@ -654,6 +654,24 @@ static void __blk_mq_complete_request_remote(void *data)
 	__blk_mq_complete_request(data);
 }
 
+static inline bool blk_mq_complete_need_ipi(struct request *rq)
+{
+	int cpu = raw_smp_processor_id();
+
+	if (!IS_ENABLED(CONFIG_SMP) ||
+	    !test_bit(QUEUE_FLAG_SAME_COMP, &rq->q->queue_flags))
+		return false;
+
+	/* same CPU or cache domain?  Complete locally */
+	if (cpu == rq->mq_ctx->cpu ||
+	    (!test_bit(QUEUE_FLAG_SAME_FORCE, &rq->q->queue_flags) &&
+	     cpus_share_cache(cpu, rq->mq_ctx->cpu)))
+		return false;
+
+	/* don't try to IPI to an offline CPU */
+	return cpu_online(rq->mq_ctx->cpu);
+}
+
 /**
  * blk_mq_complete_request - end I/O on a request
  * @rq:		the request being processed
@@ -663,11 +681,6 @@ static void __blk_mq_complete_request_remote(void *data)
  **/
 void blk_mq_complete_request(struct request *rq)
 {
-	struct blk_mq_ctx *ctx = rq->mq_ctx;
-	struct request_queue *q = rq->q;
-	bool shared = false;
-	int cpu;
-
 	WRITE_ONCE(rq->state, MQ_RQ_COMPLETE);
 
 	/*
@@ -675,25 +688,15 @@ void blk_mq_complete_request(struct request *rq)
 	 * to redirect the completion.
 	 */
 	if (rq->cmd_flags & REQ_HIPRI) {
-		q->mq_ops->complete(rq);
-		return;
-	}
-
-	if (!IS_ENABLED(CONFIG_SMP) ||
-	    !test_bit(QUEUE_FLAG_SAME_COMP, &q->queue_flags)) {
-		__blk_mq_complete_request(rq);
+		rq->q->mq_ops->complete(rq);
 		return;
 	}
 
-	cpu = raw_smp_processor_id();
-	if (!test_bit(QUEUE_FLAG_SAME_FORCE, &q->queue_flags))
-		shared = cpus_share_cache(cpu, ctx->cpu);
-
-	if (cpu != ctx->cpu && !shared && cpu_online(ctx->cpu)) {
+	if (blk_mq_complete_need_ipi(rq)) {
 		rq->csd.func = __blk_mq_complete_request_remote;
 		rq->csd.info = rq;
 		rq->csd.flags = 0;
-		smp_call_function_single_async(ctx->cpu, &rq->csd);
+		smp_call_function_single_async(rq->mq_ctx->cpu, &rq->csd);
 	} else {
 		__blk_mq_complete_request(rq);
 	}