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: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Thomas 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: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Jens Axboe <axboe@fb.com>
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@ -2116,50 +2116,18 @@ static void blk_mq_queue_reinit(struct request_queue *q,
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blk_mq_sysfs_register(q);
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}
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static int blk_mq_queue_reinit_notify(struct notifier_block *nb,
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unsigned long action, void *hcpu)
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/*
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* New online cpumask which is going to be set in this hotplug event.
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* Declare this cpumasks as global as cpu-hotplug operation is invoked
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* one-by-one and dynamically allocating this could result in a failure.
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*/
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static struct cpumask cpuhp_online_new;
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static void blk_mq_queue_reinit_work(void)
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{
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struct request_queue *q;
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int cpu = (unsigned long)hcpu;
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/*
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* New online cpumask which is going to be set in this hotplug event.
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* Declare this cpumasks as global as cpu-hotplug operation is invoked
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* one-by-one and dynamically allocating this could result in a failure.
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*/
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static struct cpumask online_new;
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/*
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* Before hotadded cpu starts handling requests, new mappings must
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* be established. Otherwise, these requests in hw queue might
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* never be dispatched.
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*
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* For example, there is a single hw queue (hctx) and two CPU queues
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* (ctx0 for CPU0, and ctx1 for CPU1).
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*
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* Now CPU1 is just onlined and a request is inserted into
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* ctx1->rq_list and set bit0 in pending bitmap as ctx1->index_hw is
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* still zero.
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*
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* And then while running hw queue, flush_busy_ctxs() finds bit0 is
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* set in pending bitmap and tries to retrieve requests in
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* hctx->ctxs[0]->rq_list. But htx->ctxs[0] is a pointer to ctx0,
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* so the request in ctx1->rq_list is ignored.
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*/
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switch (action & ~CPU_TASKS_FROZEN) {
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case CPU_DEAD:
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case CPU_UP_CANCELED:
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cpumask_copy(&online_new, cpu_online_mask);
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break;
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case CPU_UP_PREPARE:
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cpumask_copy(&online_new, cpu_online_mask);
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cpumask_set_cpu(cpu, &online_new);
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break;
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default:
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return NOTIFY_OK;
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}
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mutex_lock(&all_q_mutex);
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/*
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* We need to freeze and reinit all existing queues. Freezing
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* involves synchronous wait for an RCU grace period and doing it
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@ -2180,13 +2148,43 @@ static int blk_mq_queue_reinit_notify(struct notifier_block *nb,
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}
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list_for_each_entry(q, &all_q_list, all_q_node)
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blk_mq_queue_reinit(q, &online_new);
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blk_mq_queue_reinit(q, &cpuhp_online_new);
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list_for_each_entry(q, &all_q_list, all_q_node)
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blk_mq_unfreeze_queue(q);
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mutex_unlock(&all_q_mutex);
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return NOTIFY_OK;
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}
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static int blk_mq_queue_reinit_dead(unsigned int cpu)
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{
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cpumask_clear_cpu(cpu, &cpuhp_online_new);
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blk_mq_queue_reinit_work();
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return 0;
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}
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/*
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* Before hotadded cpu starts handling requests, new mappings must be
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* established. Otherwise, these requests in hw queue might never be
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* dispatched.
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*
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* For example, there is a single hw queue (hctx) and two CPU queues (ctx0
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* for CPU0, and ctx1 for CPU1).
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*
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* Now CPU1 is just onlined and a request is inserted into ctx1->rq_list
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* and set bit0 in pending bitmap as ctx1->index_hw is still zero.
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*
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* And then while running hw queue, flush_busy_ctxs() finds bit0 is set in
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* pending bitmap and tries to retrieve requests in hctx->ctxs[0]->rq_list.
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* But htx->ctxs[0] is a pointer to ctx0, so the request in ctx1->rq_list
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* is ignored.
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*/
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static int blk_mq_queue_reinit_prepare(unsigned int cpu)
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{
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cpumask_copy(&cpuhp_online_new, cpu_online_mask);
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cpumask_set_cpu(cpu, &cpuhp_online_new);
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blk_mq_queue_reinit_work();
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return 0;
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}
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static int __blk_mq_alloc_rq_maps(struct blk_mq_tag_set *set)
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@ -2391,8 +2389,9 @@ static int __init blk_mq_init(void)
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cpuhp_setup_state_multi(CPUHP_BLK_MQ_DEAD, "block/mq:dead", NULL,
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blk_mq_hctx_notify_dead);
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hotcpu_notifier(blk_mq_queue_reinit_notify, 0);
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cpuhp_setup_state_nocalls(CPUHP_BLK_MQ_PREPARE, "block/mq:prepare",
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blk_mq_queue_reinit_prepare,
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blk_mq_queue_reinit_dead);
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return 0;
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}
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subsys_initcall(blk_mq_init);
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