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Date: Fri, 31 Oct 2025 10:59:56 +0100
From: Christoph Hellwig <hch@lst.de>
To: Bart Van Assche <bvanassche@acm.org>
Cc: Jens Axboe <axboe@kernel.dk>, linux-block@vger.kernel.org,
	Christoph Hellwig <hch@lst.de>, Nilay Shroff <nilay@linux.ibm.com>,
	Martin Wilck <mwilck@suse.com>,
	Benjamin Marzinski <bmarzins@redhat.com>, stable@vger.kernel.org,
	Damien Le Moal <dlemoal@kernel.org>,
	Chaitanya Kulkarni <kch@nvidia.com>, Hannes Reinecke <hare@suse.de>
Subject: Re: [PATCH v3] block: Remove queue freezing from several sysfs
 store callbacks
Message-ID: <20251031095956.GB10293@lst.de>
References: <20251030172417.660949-1-bvanassche@acm.org>
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User-Agent: Mutt/1.5.17 (2007-11-01)

On Thu, Oct 30, 2025 at 10:24:17AM -0700, Bart Van Assche wrote:
> Freezing the request queue from inside sysfs store callbacks may cause a
> deadlock in combination with the dm-multipath driver and the
> queue_if_no_path option. Additionally, freezing the request queue slows
> down system boot on systems where sysfs attributes are set synchronously.
> 
> Fix this by removing the blk_mq_freeze_queue() / blk_mq_unfreeze_queue()
> calls from the store callbacks that do not strictly need these callbacks.
> This patch may cause a small delay in applying the new settings.

You'll also need data_race or READ_ONCE annotations to satisfy the
memory model.