linux-kernel - Re: [PATCH 1/2] nvmet: introduce transport layer keep-alive

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Message-ID: <bbbb8d0e-22a3-0e94-9a0a-b7ce1792a1ae@grimberg.me>
Date:   Wed, 28 Oct 2020 00:15:06 -0700
From:   Sagi Grimberg <sagi@...mberg.me>
To:     zhenwei pi <pizhenwei@...edance.com>, hch@....de,
        chaitanya.kulkarni@....com
Cc:     linux-nvme@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] nvmet: introduce transport layer keep-alive


On 10/27/20 5:15 AM, zhenwei pi wrote:
> In the zero KATO scenario, if initiator crashes without transport
> layer disconnection, target side would never reclaim resources.
> 
> A target could start transport layer keep-alive to detect dead
> connection for the admin queue.

Not sure why we should worry about kato=0, it's really
more for debug purposes. I'd rather that we block this
option from the host altogether.

> 
> Signed-off-by: zhenwei pi <pizhenwei@...edance.com>
> ---
>   drivers/nvme/target/admin-cmd.c |  2 +-
>   drivers/nvme/target/core.c      | 14 +++++++++++---
>   drivers/nvme/target/nvmet.h     |  3 ++-
>   3 files changed, 14 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/nvme/target/admin-cmd.c b/drivers/nvme/target/admin-cmd.c
> index dca34489a1dc..53fbd5c193a1 100644
> --- a/drivers/nvme/target/admin-cmd.c
> +++ b/drivers/nvme/target/admin-cmd.c
> @@ -729,7 +729,7 @@ u16 nvmet_set_feat_kato(struct nvmet_req *req)
>   
>   	nvmet_stop_keep_alive_timer(req->sq->ctrl);
>   	req->sq->ctrl->kato = DIV_ROUND_UP(val32, 1000);
> -	nvmet_start_keep_alive_timer(req->sq->ctrl);
> +	nvmet_start_keep_alive_timer(req->sq->ctrl, req);
>   
>   	nvmet_set_result(req, req->sq->ctrl->kato);
>   
> diff --git a/drivers/nvme/target/core.c b/drivers/nvme/target/core.c
> index 957b39a82431..451192f7ad6a 100644
> --- a/drivers/nvme/target/core.c
> +++ b/drivers/nvme/target/core.c
> @@ -395,10 +395,18 @@ static void nvmet_keep_alive_timer(struct work_struct *work)
>   	nvmet_ctrl_fatal_error(ctrl);
>   }
>   
> -void nvmet_start_keep_alive_timer(struct nvmet_ctrl *ctrl)
> +void nvmet_start_keep_alive_timer(struct nvmet_ctrl *ctrl, struct nvmet_req *req)
>   {
> -	if (unlikely(ctrl->kato == 0))
> +	if (unlikely(ctrl->kato == 0)) {
> +		if (req->ops->keep_alive)
> +			pr_info("ctrl %d starts with transport keep-alive %s\n", ctrl->cntlid,
> +				req->ops->keep_alive(req) ? "failed" : "succeed");
> +		else
> +			pr_info("ctrl %d starts without both NVMeOF and transport keep-alive",
> +				ctrl->cntlid);
> +
>   		return;
> +	}
>   
>   	pr_debug("ctrl %d start keep-alive timer for %d secs\n",
>   		ctrl->cntlid, ctrl->kato);
> @@ -1383,7 +1391,7 @@ u16 nvmet_alloc_ctrl(const char *subsysnqn, const char *hostnqn,
>   	ctrl->err_counter = 0;
>   	spin_lock_init(&ctrl->error_lock);
>   
> -	nvmet_start_keep_alive_timer(ctrl);
> +	nvmet_start_keep_alive_timer(ctrl, req);
>   
>   	mutex_lock(&subsys->lock);
>   	list_add_tail(&ctrl->subsys_entry, &subsys->ctrls);
> diff --git a/drivers/nvme/target/nvmet.h b/drivers/nvme/target/nvmet.h
> index 559a15ccc322..de1785ce9fcd 100644
> --- a/drivers/nvme/target/nvmet.h
> +++ b/drivers/nvme/target/nvmet.h
> @@ -305,6 +305,7 @@ struct nvmet_fabrics_ops {
>   	u16 (*install_queue)(struct nvmet_sq *nvme_sq);
>   	void (*discovery_chg)(struct nvmet_port *port);
>   	u8 (*get_mdts)(const struct nvmet_ctrl *ctrl);
> +	int (*keep_alive)(struct nvmet_req *req);
>   };
>   
>   #define NVMET_MAX_INLINE_BIOVEC	8
> @@ -395,7 +396,7 @@ void nvmet_get_feat_async_event(struct nvmet_req *req);
>   u16 nvmet_set_feat_kato(struct nvmet_req *req);
>   u16 nvmet_set_feat_async_event(struct nvmet_req *req, u32 mask);
>   void nvmet_execute_async_event(struct nvmet_req *req);
> -void nvmet_start_keep_alive_timer(struct nvmet_ctrl *ctrl);
> +void nvmet_start_keep_alive_timer(struct nvmet_ctrl *ctrl, struct nvmet_req *req);
>   void nvmet_stop_keep_alive_timer(struct nvmet_ctrl *ctrl);
>   
>   u16 nvmet_parse_connect_cmd(struct nvmet_req *req);
>