linux-kernel - [patch]blk-mq: suppress a warning

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Message-ID: <20140704112623.GA17435@kernel.org>
Date:	Fri, 4 Jul 2014 19:26:23 +0800
From:	Shaohua Li <shli@...nel.org>
To:	linux-kernel@...r.kernel.org
Cc:	axboe@...com
Subject: [patch]blk-mq: suppress a warning

The warning is hit when cpu hotplug is running. After scheduler puts a cpu
online and before blk-mq mapping reinit, a task can queue a request and run the
queue. At that time the cpu isn't in hctx->cpumask, but the cpu is mapped into
hctx 0. When the race happens, hctx->cpumask doesn't set the cpu and
ctx->index_hw/hctx->nr_ctx isn't correct, but it doesn't cause any problem. So
just suppress the warning here.

Signed-off-by: Shaohua Li <shli@...ionio.com>

diff --git a/block/blk-mq.c b/block/blk-mq.c
index ad69ef6..22f314e 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -724,7 +724,7 @@ static void __blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx)
 	LIST_HEAD(rq_list);
 	int queued;

-	WARN_ON(!cpumask_test_cpu(raw_smp_processor_id(), hctx->cpumask));
+	WARN_ON(q->mq_ops->map_queue(q, raw_smp_processor_id()) != hctx);

 	if (unlikely(test_bit(BLK_MQ_S_STOPPED, &hctx->state)))
 		return;
--
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