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Date: Mon, 6 Jan 2025 09:25:00 +0100
From: Christoph Hellwig <hch@lst.de>
To: Damien Le Moal <dlemoal@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>, linux-block@vger.kernel.org,
	linux-nvme@lists.infradead.org, Christoph Hellwig <hch@lst.de>,
	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 1/3] block: Fix sysfs queue freeze and limits lock order
Message-ID: <20250106082500.GA18408@lst.de>
References: <20250104132522.247376-1-dlemoal@kernel.org> <20250104132522.247376-2-dlemoal@kernel.org>
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In-Reply-To: <20250104132522.247376-2-dlemoal@kernel.org>
User-Agent: Mutt/1.5.17 (2007-11-01)

Did you find an exploit on my development laptop to find what I'm
working on? :)

I've got the same patch sitting here locally together with a few other
cleanups from before the holidays.  But the problem I rant into and
why I didn't finish it, is that is that the lock order doesn't work
for __blk_mq_update_nr_hw_queues which freezes at a very high level
and then does a queue limits update.  Now the whole changing of the
poll flag there look a bit questionable anyway and I was going to
look into how we could fix this, probably by retiring that flag either
just for blk-mq devices where the information can be derived from the
tagset or entirely.  I'll try to get to it ASAP.