linux-kernel - [PATCH 5.15 208/779] blk-mq: dont create hctx debugfs dir until q->debugfs

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Date:   Mon, 15 Aug 2022 19:57:32 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Yi Zhang <yi.zhang@...hat.com>,
        Ming Lei <ming.lei@...hat.com>, Christoph Hellwig <hch@....de>,
        Jens Axboe <axboe@...nel.dk>, Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.15 208/779] blk-mq: dont create hctx debugfs dir until q->debugfs_dir is created

From: Ming Lei <ming.lei@...hat.com>

[ Upstream commit f3ec5d11554778c24ac8915e847223ed71d104fc ]

blk_mq_debugfs_register_hctx() can be called by blk_mq_update_nr_hw_queues
when gendisk isn't added yet, such as nvme tcp.

Fixes the warning of 'debugfs: Directory 'hctx0' with parent '/' already present!'
which can be observed reliably when running blktests nvme/005.

Fixes: 6cfc0081b046 ("blk-mq: no need to check return value of debugfs_create functions")
Reported-by: Yi Zhang <yi.zhang@...hat.com>
Signed-off-by: Ming Lei <ming.lei@...hat.com>
Tested-by: Yi Zhang <yi.zhang@...hat.com>
Reviewed-by: Christoph Hellwig <hch@....de>
Link: https://lore.kernel.org/r/20220711090808.259682-1-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 block/blk-mq-debugfs.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/block/blk-mq-debugfs.c b/block/blk-mq-debugfs.c
index 3b38d15723de..7023257a133d 100644
--- a/block/blk-mq-debugfs.c
+++ b/block/blk-mq-debugfs.c
@@ -879,6 +879,9 @@ void blk_mq_debugfs_register_hctx(struct request_queue *q,
 	char name[20];
 	int i;
 
+	if (!q->debugfs_dir)
+		return;
+
 	snprintf(name, sizeof(name), "hctx%u", hctx->queue_num);
 	hctx->debugfs_dir = debugfs_create_dir(name, q->debugfs_dir);
 
-- 
2.35.1