Re: [PATCH v2 10/14] nvme-tcp: Use CCR to recover controller that hits an error

[Hannes Reinecke <hare@suse.de>]

On 1/30/26 23:34, Mohamed Khalfella wrote:
> An alive nvme controller that hits an error now will move to FENCING
> state instead of RESETTING state. ctrl->fencing_work attempts CCR to
> terminate inflight IOs. If CCR succeeds, switch to FENCED -> RESETTING
> and continue error recovery as usual. If CCR fails, the behavior depends
> on whether the subsystem supports CQT or not. If CQT is not supported
> then reset the controller immediately as if CCR succeeded in order to
> maintain the current behavior. If CQT is supported switch to time-based
> recovery. Schedule ctrl->fenced_work resets the controller when time
> based recovery finishes.
> 
> Either ctrl->err_work or ctrl->reset_work can run after a controller is
> fenced. Flush fencing work when either work run.
> 
> Signed-off-by: Mohamed Khalfella <mkhalfella@purestorage.com>
> ---
>   drivers/nvme/host/tcp.c | 62 ++++++++++++++++++++++++++++++++++++++++-
>   1 file changed, 61 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/nvme/host/tcp.c b/drivers/nvme/host/tcp.c
> index 69cb04406b47..af8d3b36a4bb 100644
> --- a/drivers/nvme/host/tcp.c
> +++ b/drivers/nvme/host/tcp.c
> @@ -193,6 +193,8 @@ struct nvme_tcp_ctrl {
>   	struct sockaddr_storage src_addr;
>   	struct nvme_ctrl	ctrl;
>   
> +	struct work_struct	fencing_work;
> +	struct delayed_work	fenced_work;
>   	struct work_struct	err_work;
>   	struct delayed_work	connect_work;
>   	struct nvme_tcp_request async_req;
> @@ -611,6 +613,12 @@ static void nvme_tcp_init_recv_ctx(struct nvme_tcp_queue *queue)
>   
>   static void nvme_tcp_error_recovery(struct nvme_ctrl *ctrl)
>   {
> +	if (nvme_change_ctrl_state(ctrl, NVME_CTRL_FENCING)) {
> +		dev_warn(ctrl->device, "starting controller fencing\n");
> +		queue_work(nvme_wq, &to_tcp_ctrl(ctrl)->fencing_work);
> +		return;
> +	}
> +

Don't you need to flush any outstanding 'fenced_work' queue items here
before calling 'queue_work()'?

>   	if (!nvme_change_ctrl_state(ctrl, NVME_CTRL_RESETTING))
>   		return;
>   
> @@ -2470,12 +2478,59 @@ static void nvme_tcp_reconnect_ctrl_work(struct work_struct *work)
>   	nvme_tcp_reconnect_or_remove(ctrl, ret);
>   }
>   
> +static void nvme_tcp_fenced_work(struct work_struct *work)
> +{
> +	struct nvme_tcp_ctrl *tcp_ctrl = container_of(to_delayed_work(work),
> +					struct nvme_tcp_ctrl, fenced_work);
> +	struct nvme_ctrl *ctrl = &tcp_ctrl->ctrl;
> +
> +	nvme_change_ctrl_state(ctrl, NVME_CTRL_FENCED);
> +	if (nvme_change_ctrl_state(ctrl, NVME_CTRL_RESETTING))
> +		queue_work(nvme_reset_wq, &tcp_ctrl->err_work);
> +}
> +
> +static void nvme_tcp_fencing_work(struct work_struct *work)
> +{
> +	struct nvme_tcp_ctrl *tcp_ctrl = container_of(work,
> +			struct nvme_tcp_ctrl, fencing_work);
> +	struct nvme_ctrl *ctrl = &tcp_ctrl->ctrl;
> +	unsigned long rem;
> +
> +	rem = nvme_fence_ctrl(ctrl);
> +	if (!rem)
> +		goto done;
> +
> +	if (!ctrl->cqt) {
> +		dev_info(ctrl->device,
> +			 "CCR failed, CQT not supported, skip time-based recovery\n");
> +		goto done;
> +	}
> +

As mentioned, cqt handling should be part of another patchset.

> +	dev_info(ctrl->device,
> +		 "CCR failed, switch to time-based recovery, timeout = %ums\n",
> +		 jiffies_to_msecs(rem));
> +	queue_delayed_work(nvme_wq, &tcp_ctrl->fenced_work, rem);
> +	return;
> +

Why do you need the 'fenced' workqueue at all? All it does is queing yet 
another workqueue item, which certainly can be done from the 'fencing' 
workqueue directly, no?

> +done:
> +	nvme_change_ctrl_state(ctrl, NVME_CTRL_FENCED);
> +	if (nvme_change_ctrl_state(ctrl, NVME_CTRL_RESETTING))
> +		queue_work(nvme_reset_wq, &tcp_ctrl->err_work);
> +}
> +
> +static void nvme_tcp_flush_fencing_work(struct nvme_ctrl *ctrl)
> +{
> +	flush_work(&to_tcp_ctrl(ctrl)->fencing_work);
> +	flush_delayed_work(&to_tcp_ctrl(ctrl)->fenced_work);
> +}
> +
>   static void nvme_tcp_error_recovery_work(struct work_struct *work)
>   {
>   	struct nvme_tcp_ctrl *tcp_ctrl = container_of(work,
>   				struct nvme_tcp_ctrl, err_work);
>   	struct nvme_ctrl *ctrl = &tcp_ctrl->ctrl;
>   
> +	nvme_tcp_flush_fencing_work(ctrl);

Why not 'fenced_work' ?

>   	if (nvme_tcp_key_revoke_needed(ctrl))
>   		nvme_auth_revoke_tls_key(ctrl);
>   	nvme_stop_keep_alive(ctrl);
> @@ -2518,6 +2573,7 @@ static void nvme_reset_ctrl_work(struct work_struct *work)
>   		container_of(work, struct nvme_ctrl, reset_work);
>   	int ret;
>   
> +	nvme_tcp_flush_fencing_work(ctrl);

Same.

>   	if (nvme_tcp_key_revoke_needed(ctrl))
>   		nvme_auth_revoke_tls_key(ctrl);
>   	nvme_stop_ctrl(ctrl);
> @@ -2643,13 +2699,15 @@ static enum blk_eh_timer_return nvme_tcp_timeout(struct request *rq)
>   	struct nvme_tcp_cmd_pdu *pdu = nvme_tcp_req_cmd_pdu(req);
>   	struct nvme_command *cmd = &pdu->cmd;
>   	int qid = nvme_tcp_queue_id(req->queue);
> +	enum nvme_ctrl_state state;
>   
>   	dev_warn(ctrl->device,
>   		 "I/O tag %d (%04x) type %d opcode %#x (%s) QID %d timeout\n",
>   		 rq->tag, nvme_cid(rq), pdu->hdr.type, cmd->common.opcode,
>   		 nvme_fabrics_opcode_str(qid, cmd), qid);
>   
> -	if (nvme_ctrl_state(ctrl) != NVME_CTRL_LIVE) {
> +	state = nvme_ctrl_state(ctrl);
> +	if (state != NVME_CTRL_LIVE && state != NVME_CTRL_FENCING) {

'FENCED' too, presumably?

>   		/*
>   		 * If we are resetting, connecting or deleting we should
>   		 * complete immediately because we may block controller
> @@ -2904,6 +2962,8 @@ static struct nvme_tcp_ctrl *nvme_tcp_alloc_ctrl(struct device *dev,
>   
>   	INIT_DELAYED_WORK(&ctrl->connect_work,
>   			nvme_tcp_reconnect_ctrl_work);
> +	INIT_DELAYED_WORK(&ctrl->fenced_work, nvme_tcp_fenced_work);
> +	INIT_WORK(&ctrl->fencing_work, nvme_tcp_fencing_work);
>   	INIT_WORK(&ctrl->err_work, nvme_tcp_error_recovery_work);
>   	INIT_WORK(&ctrl->ctrl.reset_work, nvme_reset_ctrl_work);
>   

Here you are calling CCR whenever error recovery is triggered.
This will cause CCR to be send from a command timeout, which is
technically wrong (CCR should be send when the KATO timeout expires,
not when a command timout expires). Both could be vastly different.

So I'd prefer to have CCR send whenever KATO timeout triggers, and
lease to current command timeout mechanism in place.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                  Kernel Storage Architect
hare@suse.de                                +49 911 74053 688
SUSE Software Solutions GmbH, Frankenstr. 146, 90461 Nürnberg
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