linux-kernel - Re: [PATCH v7 3/3] nvme-fc: Remove freeze/unfreeze around update_nr_hw

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Message-ID: <YUE5i77P7JF2zjpT@T590>
Date:   Wed, 15 Sep 2021 08:08:43 +0800
From:   Ming Lei <ming.lei@...hat.com>
To:     Daniel Wagner <dwagner@...e.de>
Cc:     linux-nvme@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Hannes Reinecke <hare@...e.de>,
        Sagi Grimberg <sagi@...mberg.me>,
        Keith Busch <kbusch@...nel.org>,
        Wen Xiong <wenxiong@...ibm.com>,
        Himanshu Madhani <himanshu.madhani@...cle.com>,
        James Smart <jsmart2021@...il.com>
Subject: Re: [PATCH v7 3/3] nvme-fc: Remove freeze/unfreeze around
 update_nr_hw_queues

On Tue, Sep 14, 2021 at 11:20:08AM +0200, Daniel Wagner wrote:
> From: James Smart <jsmart2021@...il.com>
> 
> Remove the freeze/unfreeze around changes to the number of hardware
> queues. Study and retest has indicated there are no ios that can be
> active at this point so there is nothing to freeze.
> 
> nvme-fc is draining the queues in the shutdown and error recovery path
> in __nvme_fc_abort_outstanding_ios.
> 
> This patch primarily reverts 88e837ed0f1f "nvme-fc: wait for queues to
> freeze before calling update_hr_hw_queues". It's not an exact revert as
> it leaves the adjusting of hw queues only if the count changes.
> 
> Signed-off-by: James Smart <jsmart2021@...il.com>
> [dwagner: added explanation why no IO is pending]
> Signed-off-by: Daniel Wagner <dwagner@...e.de>
> ---
>  drivers/nvme/host/fc.c | 2 --
>  1 file changed, 2 deletions(-)
> 
> diff --git a/drivers/nvme/host/fc.c b/drivers/nvme/host/fc.c
> index 6ebe68396712..aa14ad963d91 100644
> --- a/drivers/nvme/host/fc.c
> +++ b/drivers/nvme/host/fc.c
> @@ -2957,9 +2957,7 @@ nvme_fc_recreate_io_queues(struct nvme_fc_ctrl *ctrl)
>  		dev_info(ctrl->ctrl.device,
>  			"reconnect: revising io queue count from %d to %d\n",
>  			prior_ioq_cnt, nr_io_queues);
> -		nvme_wait_freeze(&ctrl->ctrl);
>  		blk_mq_update_nr_hw_queues(&ctrl->tag_set, nr_io_queues);
> -		nvme_unfreeze(&ctrl->ctrl);
>  	}

Both connect queue and ns queues are added to this tag_set, so blk_mq_update_nr_hw_queues()
will freeze them all before updating nr_hw_queues.

Reviewed-by: Ming Lei <ming.lei@...hat.com>

-- 
Ming