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>

diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
index aacf10d..9c92053 100644 (file)
--- a/block/blk-mq-tag.c
+++ b/block/blk-mq-tag.c
@@ -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;