Re: [PATCH 06/14] nvme: don't unquiesce the admin queue in nvme_kill_queues

From: Chaitanya Kulkarni <chaitanyak@nvidia.com>
To: Christoph Hellwig <hch@lst.de>, Jens Axboe <axboe@kernel.dk>,
	Keith Busch <kbusch@kernel.org>, Sagi Grimberg <sagi@grimberg.me>,
	Chao Leng <lengchao@huawei.com>
Cc: Ming Lei <ming.lei@redhat.com>,
	"linux-nvme@lists.infradead.org" <linux-nvme@lists.infradead.org>,
	"linux-block@vger.kernel.org" <linux-block@vger.kernel.org>
Subject: Re: [PATCH 06/14] nvme: don't unquiesce the admin queue in nvme_kill_queues
Date: Wed, 2 Nov 2022 01:24:10 +0000	[thread overview]
Message-ID: <b9226179-261c-b6f3-4b3c-91d2fbe02013@nvidia.com> (raw)
In-Reply-To: <20221101150050.3510-7-hch@lst.de>

On 11/1/22 08:00, Christoph Hellwig wrote:
> None of the callers of nvme_kill_queues needs it to unquiesce the
> admin queues, as all of them already do it themselves:
> 
>   1) nvme_reset_work explicit call nvme_start_admin_queue toward the
>      beginning of the function.  The extra call to nvme_start_admin_queue
>      in nvme_reset_work this won't do anything as
>      NVME_CTRL_ADMIN_Q_STOPPED will already be cleared.
>   2) nvme_remove calls nvme_dev_disable with shutdown flag set to true at
>      the very beginning of the function if the PCIe device was not present,
>      which is the precondition for the call to nvme_kill_queues.
>      nvme_dev_disable already calls nvme_start_admin_queue toward the
>      end of the function when the shutdown flag is set to true, so the
>      admin queue is already enabled at this point.
>   3) nvme_remove_dead_ctrl schedules a workqueue to unbind the driver,
>      which will end up in nvme_remove, which calls nvme_dev_disable with
>      the shutdown flag.  This case will call nvme_start_admin_queue a bit
>      later than before.
>   4) apple_nvme_remove uses the same sequence as nvme_remove_dead_ctrl
>      above.
>   5) nvme_remove_namespaces only calls nvme_kill_queues when the
>      controller is in the DEAD state.  That can only happen in the PCIe
>      driver, and only from nvme_remove. See item 2) above for the
>      conditions there.
> 
> So it is safe to just remove the call to nvme_start_admin_queue in
> nvme_kill_queues without replacement.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
> ---
>   drivers/nvme/host/core.c | 4 ----

Thanks a lot for detailed explanation..
Looks good.

Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>

-ck