Re: [PATCH v5 08/16] nvme: Implement cross-controller reset recovery

On 7/12/26 4:23 AM, Mohamed Khalfella wrote:
> A host that has more than one path connecting to an nvme subsystem
> typically has an nvme controller associated with every path. This is
> mostly applicable to nvmeof. If one path goes down, inflight IOs on that
> path should not be retried immediately on another path because this
> could lead to data corruption as described in TP4129. TP8028 defines
> cross-controller reset mechanism that can be used by host to terminate
> IOs on the failed path using one of the remaining healthy paths. Only
> after IOs are terminated, or long enough time passes as defined by
> TP4129, inflight IOs should be retried on another path. Implement core
> cross-controller reset shared logic to be used by the transports.
> 
> Signed-off-by: Mohamed Khalfella <[email protected]>
> ---
>   drivers/nvme/host/constants.c |   1 +
>   drivers/nvme/host/core.c      | 152 ++++++++++++++++++++++++++++++++++
>   drivers/nvme/host/nvme.h      |  10 +++
>   3 files changed, 163 insertions(+)
> 
> diff --git a/drivers/nvme/host/constants.c b/drivers/nvme/host/constants.c
> index dc90df9e13a2..f679efd5110e 100644
> --- a/drivers/nvme/host/constants.c
> +++ b/drivers/nvme/host/constants.c
> @@ -46,6 +46,7 @@ static const char * const nvme_admin_ops[] = {
>   	[nvme_admin_virtual_mgmt] = "Virtual Management",
>   	[nvme_admin_nvme_mi_send] = "NVMe Send MI",
>   	[nvme_admin_nvme_mi_recv] = "NVMe Receive MI",
> +	[nvme_admin_cross_ctrl_reset] = "Cross Controller Reset",
>   	[nvme_admin_dbbuf] = "Doorbell Buffer Config",
>   	[nvme_admin_format_nvm] = "Format NVM",
>   	[nvme_admin_security_send] = "Security Send",
> diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
> index 1ef4dc38f755..a1deffc3cc00 100644
> --- a/drivers/nvme/host/core.c
> +++ b/drivers/nvme/host/core.c
> @@ -571,6 +571,157 @@ void nvme_cancel_admin_tagset(struct nvme_ctrl *ctrl)
>   }
>   EXPORT_SYMBOL_GPL(nvme_cancel_admin_tagset);
>   
> +static struct nvme_ctrl *nvme_find_ctrl_ccr(struct nvme_ctrl *ictrl,
> +					    u32 min_cntlid)
> +{
> +	struct nvme_subsystem *subsys = ictrl->subsys;
> +	struct nvme_ctrl *ctrl, *sctrl = NULL;
> +	unsigned long flags;
> +	int ccr_used;
> +
> +	mutex_lock(&nvme_subsystems_lock);
> +	list_for_each_entry(ctrl, &subsys->ctrls, subsys_entry) {
> +		if (ctrl->cntlid < min_cntlid)
> +			continue;
> +
> +		spin_lock_irqsave(&ctrl->lock, flags);
> +		if (nvme_ctrl_state(ctrl) != NVME_CTRL_LIVE) {
> +			spin_unlock_irqrestore(&ctrl->lock, flags);
> +			continue;
> +		}
> +
> +		ccr_used = atomic_inc_return(&ctrl->ccr_used);
> +		if (ccr_used > ctrl->ccrl) {
> +			atomic_dec(&ctrl->ccr_used);
> +			spin_unlock_irqrestore(&ctrl->lock, flags);
> +			continue;
> +		}
> +
> +		/*
> +		 * We got a good candidate source controller that is locked and
> +		 * LIVE. However, no guarantee ctrl will not be deleted after
> +		 * ctrl->lock is released. Get a ref of both ctrl and admin_q
> +		 * so they do not disappear until we are done with them.
> +		 */
> +		WARN_ON_ONCE(!blk_get_queue(ctrl->admin_q));
> +		nvme_get_ctrl(ctrl);
> +		spin_unlock_irqrestore(&ctrl->lock, flags);
> +		sctrl = ctrl;
> +		break;
> +	}
> +	mutex_unlock(&nvme_subsystems_lock);
> +	return sctrl;
> +}
> +
> +static void nvme_put_ctrl_ccr(struct nvme_ctrl *sctrl)
> +{
> +	atomic_dec(&sctrl->ccr_used);
> +	blk_put_queue(sctrl->admin_q);
> +	nvme_put_ctrl(sctrl);
> +}
> +
> +static int nvme_issue_wait_ccr(struct nvme_ctrl *sctrl, struct nvme_ctrl *ictrl,
> +			       unsigned long deadline)
> +{
> +	struct nvme_ccr_entry ccr = { };
> +	union nvme_result res = { 0 };
> +	struct nvme_command c = { };
> +	unsigned long flags, now, tmo = 0;
> +	bool completed = false;
> +	int ret = 0;
> +	u32 result;
> +
> +	init_completion(&ccr.complete);
> +	ccr.ictrl = ictrl;
> +
> +	spin_lock_irqsave(&sctrl->lock, flags);
> +	list_add_tail(&ccr.list, &sctrl->ccr_list);
> +	spin_unlock_irqrestore(&sctrl->lock, flags);
> +
> +	c.ccr.opcode = nvme_admin_cross_ctrl_reset;
> +	c.ccr.ciu = ictrl->ciu;
> +	c.ccr.icid = cpu_to_le16(ictrl->cntlid);
> +	c.ccr.cirn = cpu_to_le64(ictrl->cirn);
> +	ret = __nvme_submit_sync_cmd(sctrl->admin_q, &c, &res,
> +				     NULL, 0, NVME_QID_ANY, 0);
> +	if (ret) {
> +		ret = -EIO;
> +		goto out;
> +	}
> +
> +	result = le32_to_cpu(res.u32);
> +	if (result & 0x01) /* Immediate Reset Successful */
> +		goto out;
> +
Do we care about any other values of 'result' ?

> +	now = jiffies;
> +	if (time_before(now, deadline))
> +		tmo = min_t(unsigned long,
> +			    secs_to_jiffies(ictrl->kato), deadline - now);
> +

Ideally we would check the request timeout for the CCR to not
exceed 'deadline'.
But as __nvme_submit_sync_cmd() doesn't allow to specify the timeout
I guess it'll be good enough for now.
(And if all goes to plan the CCR command should've been aborted in that
case anyway).

> +	if (!wait_for_completion_timeout(&ccr.complete, tmo)) {
> +		ret = -ETIMEDOUT;
> +		goto out;
> +	}
> +
> +	completed = true;
> +
> +out:
> +	spin_lock_irqsave(&sctrl->lock, flags);
> +	list_del(&ccr.list);
> +	spin_unlock_irqrestore(&sctrl->lock, flags);
> +	if (completed) {
> +		if (ccr.ccrs == NVME_CCR_STATUS_SUCCESS)
> +			return 0;
> +		return -EREMOTEIO;
> +	}
> +	return ret;
> +}
> +
> +unsigned long nvme_fence_ctrl(struct nvme_ctrl *ictrl)
> +{
> +	unsigned long now, deadline, timeout;
> +	struct nvme_ctrl *sctrl;
> +	u32 min_cntlid = 0;
> +	int ret;
> +
> +	timeout = nvme_fence_timeout_ms(ictrl);
> +	dev_info(ictrl->device, "attempting CCR, timeout %lums\n", timeout);
> +
> +	now = jiffies;
> +	deadline = jiffies + msecs_to_jiffies(timeout);
> +	while (time_before(now, deadline)) {
> +		sctrl = nvme_find_ctrl_ccr(ictrl, min_cntlid);
> +		if (!sctrl) {
> +			dev_dbg(ictrl->device,
> +				"failed to find source controller\n");
> +			return deadline - now;
> +		}
> +
> +		ret = nvme_issue_wait_ccr(sctrl, ictrl, deadline);
> +		if (!ret) {
> +			dev_info(ictrl->device, "CCR succeeded using %s\n",
> +				 dev_name(sctrl->device));
> +			nvme_put_ctrl_ccr(sctrl);
> +			return 0;
> +		}
> +
> +		/*
> +		 * CCR command or CCR operation failed on this path.
> +		 * Try another path as long as we have time.
> +		 */
> +		dev_err(ictrl->device, "CCR failed using %s, ret = %d\n",
> +			dev_name(sctrl->device), ret);
> +		min_cntlid = sctrl->cntlid + 1;
> +		nvme_put_ctrl_ccr(sctrl);
> +		now = jiffies;
> +	}
> +
> +	/* Fencing timed out call it done */
> +	dev_info(ictrl->device, "fencing timeout\n");
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(nvme_fence_ctrl);
> +
>   bool nvme_change_ctrl_state(struct nvme_ctrl *ctrl,
>   		enum nvme_ctrl_state new_state)
>   {
> @@ -5205,6 +5356,7 @@ int nvme_init_ctrl(struct nvme_ctrl *ctrl, struct device *dev,
>   
>   	mutex_init(&ctrl->scan_lock);
>   	INIT_LIST_HEAD(&ctrl->namespaces);
> +	INIT_LIST_HEAD(&ctrl->ccr_list);
>   	xa_init(&ctrl->cels);
>   	ctrl->dev = dev;
>   	ctrl->ops = ops;
> diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h
> index e558a19781bd..90b989302e21 100644
> --- a/drivers/nvme/host/nvme.h
> +++ b/drivers/nvme/host/nvme.h
> @@ -333,6 +333,13 @@ enum nvme_ctrl_flags {
>   	NVME_CTRL_FROZEN		= 6,
>   };
>   
> +struct nvme_ccr_entry {
> +	struct list_head list;
> +	struct completion complete;
> +	struct nvme_ctrl *ictrl;
> +	u8 ccrs;
> +};
> +
>   struct nvme_ctrl {
>   	bool comp_seen;
>   	bool identified;
> @@ -350,6 +357,7 @@ struct nvme_ctrl {
>   	struct blk_mq_tag_set *tagset;
>   	struct blk_mq_tag_set *admin_tagset;
>   	struct list_head namespaces;
> +	struct list_head ccr_list;
>   	struct mutex namespaces_lock;
>   	struct srcu_struct srcu;
>   	struct device ctrl_device;
> @@ -393,6 +401,7 @@ struct nvme_ctrl {
>   	u16 sqsize;
>   	u32 max_namespaces;
>   	atomic_t abort_limit;
> +	atomic_t ccr_used;
>   	u8 ccrl;
>   	u8 vwc;
>   	u32 vs;
> @@ -887,6 +896,7 @@ blk_status_t nvme_host_path_error(struct request *req);
>   bool nvme_cancel_request(struct request *req, void *data);
>   void nvme_cancel_tagset(struct nvme_ctrl *ctrl);
>   void nvme_cancel_admin_tagset(struct nvme_ctrl *ctrl);
> +unsigned long nvme_fence_ctrl(struct nvme_ctrl *ctrl);
>   bool nvme_change_ctrl_state(struct nvme_ctrl *ctrl,
>   		enum nvme_ctrl_state new_state);
>   int nvme_disable_ctrl(struct nvme_ctrl *ctrl, bool shutdown);

Otherwise looks good.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                  Kernel Storage Architect
[email protected]                                +49 911 74053 688
SUSE Software Solutions GmbH, Frankenstr. 146, 90461 Nürnberg
HRB 36809 (AG Nürnberg), GF: I. Totev, A. McDonald, W. Knoblich