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Commit 65d5291e authored by Sebastian Andrzej Siewior's avatar Sebastian Andrzej Siewior Committed by Jens Axboe
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blk-mq: Convert to new hotplug state machine 



Install the callbacks via the state machine so we can phase out the cpu
hotplug notifiers mess.

Signed-off-by: default avatarSebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: linux-block@vger.kernel.org
Cc: rt@linutronix.de
Cc: Christoph Hellwing <hch@lst.de>
Link: http://lkml.kernel.org/r/20160919212601.180033814@linutronix.de


Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarJens Axboe <axboe@fb.com>
parent 9467f859

block/blk-mq.c

+43 −44
Original line number Original line Diff line number Diff line
@@ -2116,50 +2116,18 @@ static void blk_mq_queue_reinit(struct request_queue *q, 
	blk_mq_sysfs_register(q);

	blk_mq_sysfs_register(q);

}

}





static int blk_mq_queue_reinit_notify(struct notifier_block *nb,

				      unsigned long action, void *hcpu)

{

	struct request_queue *q;

	int cpu = (unsigned long)hcpu;

/*

/*

 * New online cpumask which is going to be set in this hotplug event.

 * New online cpumask which is going to be set in this hotplug event.

 * Declare this cpumasks as global as cpu-hotplug operation is invoked

 * Declare this cpumasks as global as cpu-hotplug operation is invoked

 * one-by-one and dynamically allocating this could result in a failure.

 * one-by-one and dynamically allocating this could result in a failure.

 */

 */

	static struct cpumask online_new;

static struct cpumask cpuhp_online_new;





	/*

static void blk_mq_queue_reinit_work(void)

	 * Before hotadded cpu starts handling requests, new mappings must

{

	 * be established.  Otherwise, these requests in hw queue might

	struct request_queue *q;

	 * never be dispatched.

	 *

	 * For example, there is a single hw queue (hctx) and two CPU queues

	 * (ctx0 for CPU0, and ctx1 for CPU1).

	 *

	 * Now CPU1 is just onlined and a request is inserted into

	 * ctx1->rq_list and set bit0 in pending bitmap as ctx1->index_hw is

	 * still zero.

	 *

	 * And then while running hw queue, flush_busy_ctxs() finds bit0 is

	 * set in pending bitmap and tries to retrieve requests in

	 * hctx->ctxs[0]->rq_list.  But htx->ctxs[0] is a pointer to ctx0,

	 * so the request in ctx1->rq_list is ignored.

	 */

	switch (action & ~CPU_TASKS_FROZEN) {

	case CPU_DEAD:

	case CPU_UP_CANCELED:

		cpumask_copy(&online_new, cpu_online_mask);

		break;

	case CPU_UP_PREPARE:

		cpumask_copy(&online_new, cpu_online_mask);

		cpumask_set_cpu(cpu, &online_new);

		break;

	default:

		return NOTIFY_OK;

	}





	mutex_lock(&all_q_mutex);

	mutex_lock(&all_q_mutex);



	/*

	/*

	 * We need to freeze and reinit all existing queues.  Freezing

	 * We need to freeze and reinit all existing queues.  Freezing

	 * involves synchronous wait for an RCU grace period and doing it

	 * involves synchronous wait for an RCU grace period and doing it
@@ -2180,13 +2148,43 @@ static int blk_mq_queue_reinit_notify(struct notifier_block *nb, 
	}

	}





	list_for_each_entry(q, &all_q_list, all_q_node)

	list_for_each_entry(q, &all_q_list, all_q_node)

		blk_mq_queue_reinit(q, &online_new);

		blk_mq_queue_reinit(q, &cpuhp_online_new);





	list_for_each_entry(q, &all_q_list, all_q_node)

	list_for_each_entry(q, &all_q_list, all_q_node)

		blk_mq_unfreeze_queue(q);

		blk_mq_unfreeze_queue(q);





	mutex_unlock(&all_q_mutex);

	mutex_unlock(&all_q_mutex);

	return NOTIFY_OK;

}



static int blk_mq_queue_reinit_dead(unsigned int cpu)

{

	cpumask_clear_cpu(cpu, &cpuhp_online_new);

	blk_mq_queue_reinit_work();

	return 0;

}



/*

 * Before hotadded cpu starts handling requests, new mappings must be

 * established.  Otherwise, these requests in hw queue might never be

 * dispatched.

 *

 * For example, there is a single hw queue (hctx) and two CPU queues (ctx0

 * for CPU0, and ctx1 for CPU1).

 *

 * Now CPU1 is just onlined and a request is inserted into ctx1->rq_list

 * and set bit0 in pending bitmap as ctx1->index_hw is still zero.

 *

 * And then while running hw queue, flush_busy_ctxs() finds bit0 is set in

 * pending bitmap and tries to retrieve requests in hctx->ctxs[0]->rq_list.

 * But htx->ctxs[0] is a pointer to ctx0, so the request in ctx1->rq_list

 * is ignored.

 */

static int blk_mq_queue_reinit_prepare(unsigned int cpu)

{

	cpumask_copy(&cpuhp_online_new, cpu_online_mask);

	cpumask_set_cpu(cpu, &cpuhp_online_new);

	blk_mq_queue_reinit_work();

	return 0;

}

}





static int __blk_mq_alloc_rq_maps(struct blk_mq_tag_set *set)

static int __blk_mq_alloc_rq_maps(struct blk_mq_tag_set *set)
@@ -2391,8 +2389,9 @@ static int __init blk_mq_init(void) 
	cpuhp_setup_state_multi(CPUHP_BLK_MQ_DEAD, "block/mq:dead", NULL,

	cpuhp_setup_state_multi(CPUHP_BLK_MQ_DEAD, "block/mq:dead", NULL,

				blk_mq_hctx_notify_dead);

				blk_mq_hctx_notify_dead);





	hotcpu_notifier(blk_mq_queue_reinit_notify, 0);

	cpuhp_setup_state_nocalls(CPUHP_BLK_MQ_PREPARE, "block/mq:prepare",



				  blk_mq_queue_reinit_prepare,

				  blk_mq_queue_reinit_dead);

	return 0;

	return 0;

}

}

subsys_initcall(blk_mq_init);
 
subsys_initcall(blk_mq_init);