Commit a9a80808 authored Oct 25, 2019 by Bart Van Assche Committed by Jens Axboe Oct 25, 2019

block: Remove the synchronize_rcu() call from __blk_mq_update_nr_hw_queues()



Since the blk_mq_{,un}freeze_queue() calls in __blk_mq_update_nr_hw_queues()
already serialize __blk_mq_update_nr_hw_queues() against
blk_mq_queue_tag_busy_iter(), the synchronize_rcu() call in
__blk_mq_update_nr_hw_queues() is not necessary. Hence remove it.

Note: the synchronize_rcu() call in __blk_mq_update_nr_hw_queues() was
introduced by commit f5bbbbe4 ("blk-mq: sync the update nr_hw_queues with
blk_mq_queue_tag_busy_iter"). Commit 530ca2c9 ("blk-mq: Allow blocking
queue tag iter callbacks") removed the rcu_read_{,un}lock() calls that
correspond to the synchronize_rcu() call in __blk_mq_update_nr_hw_queues().

Reviewed-by: Ming Lei <ming.lei@redhat.com>
Cc: Jianchao Wang <jianchao.w.wang@oracle.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Hannes Reinecke <hare@suse.com>
Cc: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

parent 48d9b0d4

block/blk-mq.c

+0 −4

Original line number	Diff line number	Diff line
		@@ -3242,10 +3242,6 @@ static void __blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set,

		list_for_each_entry(q, &set->tag_list, tag_set_list)
		blk_mq_freeze_queue(q);
		/*
		* Sync with blk_mq_queue_tag_busy_iter.
		*/
		synchronize_rcu();
		/*
		* Switch IO scheduler to 'none', cleaning up the data associated
		* with the previous scheduler. We will switch back once we are done

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