linux-kernel - Re: [PATCH 2/2] nvme-fc: Wait with a timeout for queue to freeze

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Message-ID: <YNp50pmlzN6M0kNX@T590>
Date:   Tue, 29 Jun 2021 09:39:30 +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,
        James Smart <james.smart@...adcom.com>,
        Keith Busch <kbusch@...nel.org>, Jens Axboe <axboe@...com>,
        Sagi Grimberg <sagi@...mberg.me>
Subject: Re: [PATCH 2/2] nvme-fc: Wait with a timeout for queue to freeze

On Fri, Jun 25, 2021 at 12:16:49PM +0200, Daniel Wagner wrote:
> Do not wait indifinitly for all queues to freeze. Instead use a
> timeout and abort the operation if we get stuck.
> 
> Signed-off-by: Daniel Wagner <dwagner@...e.de>
> ---
>  drivers/nvme/host/fc.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/nvme/host/fc.c b/drivers/nvme/host/fc.c
> index a9645cd89eca..d8db85aa5417 100644
> --- a/drivers/nvme/host/fc.c
> +++ b/drivers/nvme/host/fc.c
> @@ -2955,7 +2955,14 @@ 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);
> +		if (!nvme_wait_freeze_timeout(&ctrl->ctrl, NVME_IO_TIMEOUT)) {
> +			/*
> +			 * If we timed out waiting for freeze we are likely to
> +			 * be stuck.  Fail the controller initialization just
> +			 * to be safe.
> +			 */
> +			return -ENODEV;
> +		}
>  		blk_mq_update_nr_hw_queues(&ctrl->tag_set, nr_io_queues);
>  		nvme_unfreeze(&ctrl->ctrl);

Can you investigate a bit on why there is the hang? FC shouldn't use
managed IRQ, so the interrupt won't be shutdown.

blk-mq debugfs may help to dump the requests after the hang is triggered,
or you still can add debug code in nvme_wait_freeze_timeout() to dump
all requests if blk-mq debugfs doesn't work.


Thanks,
Ming