blk-mq-debugfs: add missing debugfs_mutex in blk_mq_debugfs_register_hctxs()

In blk_mq_update_nr_hw_queues(), debugfs_mutex is not held while
creating debugfs entries for hctxs. Hence add debugfs_mutex there,
it's safe because queue is not frozen.

Signed-off-by: Yu Kuai <yukuai@fnnas.com>
Reviewed-by: Nilay Shroff <nilay@linux.ibm.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/blk-mq-debugfs.c b/block/blk-mq-debugfs.c
index 22c182b40bc3f6cf353b5063b02fd2782303708b..5c7cadf51a88f007dfc929da1105344f377ee67e 100644 (file)
--- a/block/blk-mq-debugfs.c
+++ b/block/blk-mq-debugfs.c
@@ -679,8 +679,10 @@ void blk_mq_debugfs_register_hctxs(struct request_queue *q)
        struct blk_mq_hw_ctx *hctx;
        unsigned long i;
 
+       mutex_lock(&q->debugfs_mutex);
        queue_for_each_hw_ctx(q, hctx, i)
                blk_mq_debugfs_register_hctx(q, hctx);
+       mutex_unlock(&q->debugfs_mutex);
 }
 
 void blk_mq_debugfs_unregister_hctxs(struct request_queue *q)