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

hailan94 · axboe · commit 9d20fd6ce1ba · 2026-02-02T07:05:19.000-07:00
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 &lt;yukuai@fnnas.com&gt;
Reviewed-by: Nilay Shroff &lt;nilay@linux.ibm.com&gt;
Reviewed-by: Ming Lei &lt;ming.lei@redhat.com&gt;
Reviewed-by: Hannes Reinecke &lt;hare@suse.de&gt;
Signed-off-by: Jens Axboe &lt;axboe@kernel.dk&gt;
diff --git 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)

Original file line number	Diff line number	Diff line change
`@@ -679,8 +679,10 @@ void blk_mq_debugfs_register_hctxs(struct request_queue *q)`
`679`	`679`	`struct blk_mq_hw_ctx *hctx;`
`680`	`680`	`unsigned long i;`
`681`	`681`
	`682`	`+ mutex_lock(&q->debugfs_mutex);`
`682`	`683`	`queue_for_each_hw_ctx(q, hctx, i)`
`683`	`684`	`blk_mq_debugfs_register_hctx(q, hctx);`
	`685`	`+ mutex_unlock(&q->debugfs_mutex);`
`684`	`686`	`}`
`685`	`687`
`686`	`688`	`void blk_mq_debugfs_unregister_hctxs(struct request_queue *q)`