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Subject: Re: [PATCH v5 3/3] nvme-fc: fix controller reset hang during traffic
To:     Daniel Wagner <dwagner@suse.de>, linux-nvme@lists.infradead.org
Cc:     linux-kernel@vger.kernel.org,
        James Smart <james.smart@broadcom.com>,
        Keith Busch <kbusch@kernel.org>,
        Ming Lei <ming.lei@redhat.com>,
        Sagi Grimberg <sagi@grimberg.me>,
        Wen Xiong <wenxiong@us.ibm.com>,
        Himanshu Madhani <himanshu.madhani@oracle.com>,
        James Smart <jsmart2021@gmail.com>
References: <20210818120530.130501-1-dwagner@suse.de>
 <20210818120530.130501-4-dwagner@suse.de>
From:   Hannes Reinecke <hare@suse.de>
Message-ID: <ba6ebacb-6554-7683-7a7f-577241356bfa@suse.de>
Date:   Wed, 18 Aug 2021 14:21:51 +0200
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On 8/18/21 2:05 PM, Daniel Wagner wrote:
> From: James Smart <jsmart2021@gmail.com>
> 
> commit fe35ec58f0d3 ("block: update hctx map when use multiple maps")
> exposed an issue where we may hang trying to wait for queue freeze
> during I/O. We call blk_mq_update_nr_hw_queues which may attempt to freeze
> the queue. However we never started queue freeze when starting the
> reset, which means that we have inflight pending requests that entered the
> queue that we will not complete once the queue is quiesced.
> 
> So start a freeze before we quiesce the queue, and unfreeze the queue
> after we successfully connected the I/O queues (the unfreeze is already
> present in the code). blk_mq_update_nr_hw_queues will be called only
> after we are sure that the queue was already frozen.
> 
> This follows to how the pci driver handles resets.
> 
> This patch added logic introduced in commit 9f98772ba307 "nvme-rdma: fix
> controller reset hang during traffic".
> 
> Signed-off-by: James Smart <jsmart2021@gmail.com>
> CC: Sagi Grimberg <sagi@grimberg.me>
> Tested-by: Daniel Wagner <dwagner@suse.de>
> Reviewed-by: Daniel Wagner <dwagner@suse.de>
> ---
>  drivers/nvme/host/fc.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/nvme/host/fc.c b/drivers/nvme/host/fc.c
> index 3ff783a2e9f7..99dadab2724c 100644
> --- a/drivers/nvme/host/fc.c
> +++ b/drivers/nvme/host/fc.c
> @@ -2974,9 +2974,10 @@ nvme_fc_recreate_io_queues(struct nvme_fc_ctrl *ctrl)
>  			return -ENODEV;
>  		}
>  		blk_mq_update_nr_hw_queues(&ctrl->tag_set, nr_io_queues);
> -		nvme_unfreeze(&ctrl->ctrl);
>  	}
>  
> +	nvme_unfreeze(&ctrl->ctrl);
> +
>  	return 0;
>  
>  out_delete_hw_queues:
> @@ -3215,6 +3216,9 @@ nvme_fc_delete_association(struct nvme_fc_ctrl *ctrl)
>  	ctrl->iocnt = 0;
>  	spin_unlock_irqrestore(&ctrl->lock, flags);
>  
> +	if (ctrl->ctrl.queue_count > 1)
> +		nvme_start_freeze(&ctrl->ctrl);
> +
>  	__nvme_fc_abort_outstanding_ios(ctrl, false);
>  
>  	/* kill the aens as they are a separate path */
> 
Reviewed-by: Hannes Reinecke <hare@suse.de>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		           Kernel Storage Architect
hare@suse.de			                  +49 911 74053 688
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