Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Tue, 15 Feb 2022 19:47:04 +0100
From:   Christoph Hellwig <hch@lst.de>
To:     Keith Busch <kbusch@kernel.org>
Cc:     Markus =?iso-8859-1?Q?Bl=F6chl?= <markus.bloechl@ipetronik.com>,
        Jens Axboe <axboe@kernel.dk>, Christoph Hellwig <hch@lst.de>,
        Sagi Grimberg <sagi@grimberg.me>,
        linux-nvme@lists.infradead.org, linux-block@vger.kernel.org,
        linux-kernel@vger.kernel.org, Stefan Roese <sr@denx.de>
Subject: Re: [RFC PATCH] nvme: prevent hang on surprise removal of NVMe disk
Message-ID: <20220215184704.GB24543@lst.de>
References: <20220214095107.3t5en5a3tosaeoo6@ipetronik.com> <20220215152240.GB1663897@dhcp-10-100-145-180.wdc.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20220215152240.GB1663897@dhcp-10-100-145-180.wdc.com>
User-Agent: Mutt/1.5.17 (2007-11-01)
Precedence: bulk

On Tue, Feb 15, 2022 at 07:22:40AM -0800, Keith Busch wrote:
> I can't actually tell if not checking the DYING flag check was
> intentional or not, since the comments in blk_queue_start_drain() say
> otherwise.
> 
> Christoph, do you know the intention here? Should __bio_queue_enter()
> check the queue DYING flag, or do you prefer drivers explicity set the
> disk state like this? It looks to me the queue flags should be checked
> since that's already tied to the freeze wait_queue_head_t.

It was intentional but maybe not fully thought out.  Do you remember why
we're doing the manual setting of the dying flag instead of just calling
del_gendisk early on in nvme?  Because calling del_gendisk is supposed
to be all that a tree needs to do.