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Date: Tue, 10 Feb 2026 16:41:50 +0100
From: Christoph Hellwig <hch@lst.de>
To: Keith Busch <kbusch@kernel.org>
Cc: Bart Van Assche <bvanassche@acm.org>, Yu Kuai <yukuai@fnnas.com>,
	axboe@kernel.dk, hch@lst.de, sagi@grimberg.me, sven@kernel.org,
	j@jannau.net, linux-block@vger.kernel.org,
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	ming.lei@redhat.com, neal@gompa.dev, asahi@lists.linux.dev,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 4/4] blk-mq: use blk_queue_enter/exit to protect
 debugfs file creation
Message-ID: <20260210154150.GA2844@lst.de>
References: <20260209082953.3053721-1-yukuai@fnnas.com> <20260209082953.3053721-5-yukuai@fnnas.com> <6b18e0bc-efa7-4bd5-b12b-a313941d2ba1@acm.org> <aYoaWwI-sl5hK6s_@kbusch-mbp>
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On Mon, Feb 09, 2026 at 10:33:15AM -0700, Keith Busch wrote:
> > This is not clear to me. Why are concurrent queue freezes not allowed
> > while debugfs attributes are created? I don't see any code in debugfs
> > that calls back into the block layer while creating debugfs attributes?
> > Did I perhaps overlook something?
> 
> I had to look up the original commit that introduced the WARN,
> 65d466b629847. The commit message says "Creating new debugfs entries can
> trigger fs reclaim", so that must be the path that enters back into the
> blaock layer request_queue.

Another way to solves this would be to scope all the debugs action
as NOIO context.