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block-mq: fix comments in blk_mq_queue_tag_busy_iter 

'f5bbbbe4d635 ("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 '530ca2c9bd69 ("blk-mq: Allow blocking queue tag iter
callbacks")' fix it by get request_queue's ref. And 'a9a808084d6a ("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>
zero-sugar-mainline-defconfig
yangerkun 2020-09-19 11:54:25 +08:00 committed by Jens Axboe
parent 8229cca8c3
commit 76cffccd60
1 changed files with 1 additions and 3 deletions
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4
block/blk-mq-tag.c
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@ -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;