linux-kernel - [PATCH 1/2] blk-mq: handle single queue case in blk_mq_hctx_next

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Date:	Mon,  3 Nov 2014 09:23:27 +0100
From:	Christoph Hellwig <hch@....de>
To:	Jens Axboe <axboe@...com>
Cc:	Richard Weinberger <richard@....at>,
	Ming Lei <tom.leiming@...il.com>, ceph-devel@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH 1/2] blk-mq: handle single queue case in blk_mq_hctx_next_cpu

Don't duplicate the code to handle the not cpu bounce case in the
caller, do it inside blk_mq_hctx_next_cpu instead.

Signed-off-by: Christoph Hellwig <hch@....de>
---
 block/blk-mq.c | 34 +++++++++++++---------------------
 1 file changed, 13 insertions(+), 21 deletions(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index b355b59..22e50a5 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -780,10 +780,11 @@ static void __blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx)
  */
 static int blk_mq_hctx_next_cpu(struct blk_mq_hw_ctx *hctx)
 {
-	int cpu = hctx->next_cpu;
+	if (hctx->queue->nr_hw_queues == 1)
+		return WORK_CPU_UNBOUND;
 
 	if (--hctx->next_cpu_batch <= 0) {
-		int next_cpu;
+		int cpu = hctx->next_cpu, next_cpu;
 
 		next_cpu = cpumask_next(hctx->next_cpu, hctx->cpumask);
 		if (next_cpu >= nr_cpu_ids)
@@ -791,9 +792,11 @@ static int blk_mq_hctx_next_cpu(struct blk_mq_hw_ctx *hctx)
 
 		hctx->next_cpu = next_cpu;
 		hctx->next_cpu_batch = BLK_MQ_CPU_WORK_BATCH;
+	
+		return cpu;
 	}
 
-	return cpu;
+	return hctx->next_cpu;
 }
 
 void blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx, bool async)
@@ -801,16 +804,13 @@ void blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx, bool async)
 	if (unlikely(test_bit(BLK_MQ_S_STOPPED, &hctx->state)))
 		return;
 
-	if (!async && cpumask_test_cpu(smp_processor_id(), hctx->cpumask))
+	if (!async && cpumask_test_cpu(smp_processor_id(), hctx->cpumask)) {
 		__blk_mq_run_hw_queue(hctx);
-	else if (hctx->queue->nr_hw_queues == 1)
-		kblockd_schedule_delayed_work(&hctx->run_work, 0);
-	else {
-		unsigned int cpu;
-
-		cpu = blk_mq_hctx_next_cpu(hctx);
-		kblockd_schedule_delayed_work_on(cpu, &hctx->run_work, 0);
+		return;
 	}
+
+	kblockd_schedule_delayed_work_on(blk_mq_hctx_next_cpu(hctx),
+			&hctx->run_work, 0);
 }
 
 void blk_mq_run_queues(struct request_queue *q, bool async)
@@ -908,16 +908,8 @@ static void blk_mq_delay_work_fn(struct work_struct *work)
 
 void blk_mq_delay_queue(struct blk_mq_hw_ctx *hctx, unsigned long msecs)
 {
-	unsigned long tmo = msecs_to_jiffies(msecs);
-
-	if (hctx->queue->nr_hw_queues == 1)
-		kblockd_schedule_delayed_work(&hctx->delay_work, tmo);
-	else {
-		unsigned int cpu;
-
-		cpu = blk_mq_hctx_next_cpu(hctx);
-		kblockd_schedule_delayed_work_on(cpu, &hctx->delay_work, tmo);
-	}
+	kblockd_schedule_delayed_work_on(blk_mq_hctx_next_cpu(hctx),
+			&hctx->delay_work, msecs_to_jiffies(msecs));
 }
 EXPORT_SYMBOL(blk_mq_delay_queue);
 
-- 
1.9.1

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