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Date: Fri, 25 Apr 2025 20:38:01 +0200
From: Christoph Hellwig <hch@lst.de>
To: Ming Lei <ming.lei@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>, linux-block@vger.kernel.org,
	Nilay Shroff <nilay@linux.ibm.com>,
	Shinichiro Kawasaki <shinichiro.kawasaki@wdc.com>,
	Thomas =?iso-8859-1?Q?Hellstr=F6m?= <thomas.hellstrom@linux.intel.com>,
	Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH V3 17/20] block: move debugfs/sysfs register out of
 freezing queue
Message-ID: <20250425183801.GC26393@lst.de>
References: <20250424152148.1066220-1-ming.lei@redhat.com> <20250424152148.1066220-18-ming.lei@redhat.com>
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In-Reply-To: <20250424152148.1066220-18-ming.lei@redhat.com>
User-Agent: Mutt/1.5.17 (2007-11-01)

On Thu, Apr 24, 2025 at 11:21:40PM +0800, Ming Lei wrote:
> Move debugfs/sysfs register out of freezing queue in
> __blk_mq_update_nr_hw_queues(), so that the following lockdep dependency
> can be killed:
> 
> 	#2 (&q->q_usage_counter(io)#16){++++}-{0:0}:
> 	#1 (fs_reclaim){+.+.}-{0:0}:
> 	#0 (&sb->s_type->i_mutex_key#3){+.+.}-{4:4}: //debugfs
> 
> And registering/un-registering debugfs/sysfs does not require queue to be
> frozen.

Please explain the why it's not required.  And talking about lockdep
dependencies is not very useful - it either is an actual lock ordering
issue or a fale positive, but lockdep is just the messenger.