blk-mq-debugfs: fix device sched directory for default scheduler

In blk_mq_debugfs_register(), I remembered to set up the per-hctx sched
directories if a default scheduler was already configured by
blk_mq_sched_init() from blk_mq_init_allocated_queue(), but I didn't do
the same for the device-wide sched directory. Fix it.

Fixes: d332ce09 ("blk-mq-debugfs: allow schedulers to register debugfs attributes")
Signed-off-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block/blk-mq-debugfs.c

@@ -815,10 +815,14 @@ int blk_mq_debugfs_register(struct request_queue *q)
 		goto err;
 
 	/*
-	 * blk_mq_init_hctx() attempted to do this already, but q->debugfs_dir
+	 * blk_mq_init_sched() attempted to do this already, but q->debugfs_dir
 	 * didn't exist yet (because we don't know what to name the directory
 	 * until the queue is registered to a gendisk).
 	 */
+	if (q->elevator && !q->sched_debugfs_dir)
+		blk_mq_debugfs_register_sched(q);
+
+	/* Similarly, blk_mq_init_hctx() couldn't do this previously. */
 	queue_for_each_hw_ctx(q, hctx, i) {
 		if (!hctx->debugfs_dir && blk_mq_debugfs_register_hctx(q, hctx))
 			goto err;