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Tejun Heo authored
q->mq_usage_counter is a percpu_ref which is killed and drained when the queue is frozen. On a CPU hotplug event, blk_mq_queue_reinit() which involves freezing the queue is invoked on all existing queues. Because percpu_ref killing and draining involve a RCU grace period, doing the above on one queue after another may take a long time if there are many queues on the system. This patch splits out initiation of freezing and waiting for its completion, and updates blk_mq_queue_reinit_notify() so that the queues are frozen in parallel instead of one after another. Note that freezing and unfreezing are moved from blk_mq_queue_reinit() to blk_mq_queue_reinit_notify(). Signed-off-by:
Tejun Heo <tj@kernel.org> Reported-by:
Christian Borntraeger <borntraeger@de.ibm.com> Tested-by:
Christian Borntraeger <borntraeger@de.ibm.com> Signed-off-by:
Jens Axboe <axboe@fb.com>
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