linux-kernel - Re: [PATCH v4 6/8] nvme-fc: fix controller reset hang during traffic

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Message-ID: <a2049faa-888c-af80-9401-a8ba4defec53@oracle.com>
Date:   Mon, 2 Aug 2021 14:39:01 -0500
From:   Himanshu Madhani <himanshu.madhani@...cle.com>
To:     Daniel Wagner <dwagner@...e.de>, linux-nvme@...ts.infradead.org
Cc:     linux-kernel@...r.kernel.org,
        James Smart <james.smart@...adcom.com>,
        Keith Busch <kbusch@...nel.org>,
        Ming Lei <ming.lei@...hat.com>,
        Sagi Grimberg <sagi@...mberg.me>,
        Hannes Reinecke <hare@...e.de>,
        Wen Xiong <wenxiong@...ibm.com>,
        James Smart <jsmart2021@...il.com>
Subject: Re: [PATCH v4 6/8] nvme-fc: fix controller reset hang during traffic



On 8/2/21 6:26 AM, Daniel Wagner wrote:
> From: James Smart <jsmart2021@...il.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@...il.com>
> CC: Sagi Grimberg <sagi@...mberg.me>
> [dwagner: call nvme_unfreeze() unconditionally in
>            nvme_fc_recreate_io_queues() to match the nvme_start_freeze()]
> Tested-by: Daniel Wagner <dwagner@...e.de>
> Reviewed-by: Daniel Wagner <dwagner@...e.de>
> ---
>   drivers/nvme/host/fc.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/nvme/host/fc.c b/drivers/nvme/host/fc.c
> index 133b87db4f1d..b292af0fd655 100644
> --- a/drivers/nvme/host/fc.c
> +++ b/drivers/nvme/host/fc.c
> @@ -2486,6 +2486,7 @@ __nvme_fc_abort_outstanding_ios(struct nvme_fc_ctrl *ctrl, bool start_queues)
>   	 * (but with error status).
>   	 */
>   	if (ctrl->ctrl.queue_count > 1) {
> +		nvme_start_freeze(&ctrl->ctrl);
>   		nvme_stop_queues(&ctrl->ctrl);
>   		nvme_sync_io_queues(&ctrl->ctrl);
>   		blk_mq_tagset_busy_iter(&ctrl->tag_set,
> @@ -2966,8 +2967,8 @@ 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);
>   
>   	ret = nvme_fc_create_hw_io_queues(ctrl, ctrl->ctrl.sqsize + 1);
>   	if (ret)
> 

Reviewed-by: Himanshu Madhani <himanshu.madhani@...cle.com>

-- 
Himanshu Madhani                                Oracle Linux Engineering