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Date:   Wed, 20 Jul 2022 15:08:45 +0200
From:   Christoph Hellwig <hch@lst.de>
To:     Ming Lei <ming.lei@redhat.com>
Cc:     Christoph Hellwig <hch@lst.de>, axboe@kernel.dk,
        linux-block@vger.kernel.org
Subject: Re: [PATCH 2/2] Revert "ublk_drv: fix request queue leak"
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References: <20220718062928.335399-1-hch@lst.de> <20220718062928.335399-2-hch@lst.de> <YtalgzqC/q3JpYCR@T590> <20220720060705.GB6734@lst.de> <YtezD/apQ1dM0n33@T590> <20220720090040.GA18210@lst.de> <YtfXmlbhN9WAPK71@T590>
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On Wed, Jul 20, 2022 at 06:23:22PM +0800, Ming Lei wrote:
> Even though alloc_disk and add_disk is paired here, GD_OWNS_QUEUE still
> can't be set because request queue has to be workable for the new alloc/
> added disk, just like scsi.

How so?  dm has totally normall disk/request_queue lifetimes.  The only
caveat is that the blk-mq bits of the queue are added after the initial
non-mq disk allocation.  There is no newly added disk after the disk
and queue are torn down.