Commit 76cffccd authored Sep 19, 2020 by yangerkun Committed by Jens Axboe Sep 29, 2020

block-mq: fix comments in blk_mq_queue_tag_busy_iter



'f5bbbbe4 ("blk-mq: sync the update nr_hw_queues with
blk_mq_queue_tag_busy_iter")' introduce a bug what we may sleep between
rcu lock. Then '530ca2c9 ("blk-mq: Allow blocking queue tag iter
callbacks")' fix it by get request_queue's ref. And 'a9a80808 ("block:
Remove the synchronize_rcu() call from __blk_mq_update_nr_hw_queues()")'
remove the synchronize_rcu in __blk_mq_update_nr_hw_queues. We need
update the confused comments in blk_mq_queue_tag_busy_iter.

Signed-off-by: yangerkun <yangerkun@huawei.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

parent 8229cca8

block/blk-mq-tag.c

+1 −3

Original line number	Diff line number	Diff line
		@@ -416,9 +416,7 @@ void blk_mq_queue_tag_busy_iter(struct request_queue q, busy_iter_fn fn,
		/*
		* __blk_mq_update_nr_hw_queues() updates nr_hw_queues and queue_hw_ctx
		* while the queue is frozen. So we can use q_usage_counter to avoid
		* racing with it. __blk_mq_update_nr_hw_queues() uses
		* synchronize_rcu() to ensure this function left the critical section
		* below.
		* racing with it.
		*/
		if (!percpu_ref_tryget(&q->q_usage_counter))
		return;

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