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Date: Mon, 6 Jan 2025 11:00:02 +0100
From: Christoph Hellwig <hch@lst.de>
To: Damien Le Moal <dlemoal@kernel.org>
Cc: Christoph Hellwig <hch@lst.de>, Jens Axboe <axboe@kernel.dk>,
	linux-block@vger.kernel.org, linux-nvme@lists.infradead.org,
	Keith Busch <kbusch@kernel.org>, Sagi Grimberg <sagi@grimberg.me>,
	Ming Lei <ming.lei@redhat.com>, Nilay Shroff <nilay@linux.ibm.com>
Subject: Re: [PATCH 2/3] block: Fix __blk_mq_update_nr_hw_queues() queue
 freeze and limits lock order
Message-ID: <20250106100002.GA20647@lst.de>
References: <20250104132522.247376-1-dlemoal@kernel.org> <20250104132522.247376-3-dlemoal@kernel.org> <20250106083014.GD18408@lst.de> <30064337-9fe1-47c7-b4ec-c999b06a1b47@kernel.org>
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On Mon, Jan 06, 2025 at 06:58:00PM +0900, Damien Le Moal wrote:
> Ah, yes, that would potentially be an issue... Hmmm... Maybe a better solution
> would be to move the start update out of the main loop and do it first, before
> the freeze. What I do not fully understand with the code of this function is
> that it does freeze and limit update for each tag list of the tag set, but
> there is only a single request queue for all of them. So I am confused. Why
> does the blk_mq_freeze_queue and poll limit setting have to be done in the loop
> multiple times for each tag list ? I do not see it... If we can move these out
> of the tag list loops, then correcting the ordering becomes easy.

I've come up with a version that simply never updates the flag. About
to send it out.