Re: [PATCH v4 09/15] nvme: Implement cross-controller reset completion

[Mohamed Khalfella]

On Tue 2026-04-07 07:48:50 +0200, Hannes Reinecke wrote:
> On 3/31/26 18:55, Mohamed Khalfella wrote:
> > On Mon 2026-03-30 12:53:07 +0200, Hannes Reinecke wrote:
> >> On 3/28/26 01:43, Mohamed Khalfella wrote:
> >>> An nvme source controller that issues CCR command expects to receive an
> >>> NVME_AER_NOTICE_CCR_COMPLETED when pending CCR succeeds or fails. Add
> >>> sctrl->ccr_work to read NVME_LOG_CCR logpage and wakeup any thread
> >>> waiting on CCR completion.
> >>>
> >>> Signed-off-by: Mohamed Khalfella <mkhalfella@xxxxxxxxxxxxxxx>
> >>> ---
> >>>    drivers/nvme/host/core.c | 49 +++++++++++++++++++++++++++++++++++++++-
> >>>    drivers/nvme/host/nvme.h |  1 +
> >>>    2 files changed, 49 insertions(+), 1 deletion(-)
> >>>
> >>> diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
> >>> index 5603ae36444f..793f203bfc38 100644
> >>> --- a/drivers/nvme/host/core.c
> >>> +++ b/drivers/nvme/host/core.c
> >>> @@ -1920,7 +1920,8 @@ EXPORT_SYMBOL_GPL(nvme_set_queue_count);
> >>>    
> >>>    #define NVME_AEN_SUPPORTED \
> >>>    	(NVME_AEN_CFG_NS_ATTR | NVME_AEN_CFG_FW_ACT | \
> >>> -	 NVME_AEN_CFG_ANA_CHANGE | NVME_AEN_CFG_DISC_CHANGE)
> >>> +	 NVME_AEN_CFG_ANA_CHANGE | NVME_AEN_CFG_CCR_COMPLETE | \
> >>> +	 NVME_AEN_CFG_DISC_CHANGE)
> >>>    
> >>>    static void nvme_enable_aen(struct nvme_ctrl *ctrl)
> >>>    {
> >>> @@ -4873,6 +4874,47 @@ static void nvme_get_fw_slot_info(struct nvme_ctrl *ctrl)
> >>>    	kfree(log);
> >>>    }
> >>>    
> >>> +static void nvme_ccr_work(struct work_struct *work)
> >>> +{
> >>> +	struct nvme_ctrl *ctrl = container_of(work, struct nvme_ctrl, ccr_work);
> >>> +	struct nvme_ccr_entry *ccr;
> >>> +	struct nvme_ccr_log_entry *entry;
> >>> +	struct nvme_ccr_log *log;
> >>> +	unsigned long flags;
> >>> +	int ret, i;
> >>> +
> >>> +	log = kmalloc(sizeof(*log), GFP_KERNEL);
> >>> +	if (!log)
> >>> +		return;
> >>> +
> >>> +	ret = nvme_get_log(ctrl, 0, NVME_LOG_CCR, 0x01,
> >>> +			   0x00, log, sizeof(*log), 0);
> >>> +	if (ret)
> >>> +		goto out;
> >>> +
> >>> +	spin_lock_irqsave(&ctrl->lock, flags);
> >>> +	for (i = 0; i < le16_to_cpu(log->ne); i++) {
> >>> +		entry = &log->entries[i];
> >>> +		if (entry->ccrs == NVME_CCR_STATUS_IN_PROGRESS)
> >>> +			continue;
> >>> +
> >>> +		list_for_each_entry(ccr, &ctrl->ccr_list, list) {
> >>> +			struct nvme_ctrl *ictrl = ccr->ictrl;
> >>> +
> >>> +			if (ictrl->cntlid != le16_to_cpu(entry->icid) ||
> >>> +			    ictrl->ciu != entry->ciu)
> >>> +				continue;
> >>> +
> >>> +			/* Complete matching entry */
> >>> +			ccr->ccrs = entry->ccrs;
> >>> +			complete(&ccr->complete);
> >>> +		}
> >>> +	}
> >>> +	spin_unlock_irqrestore(&ctrl->lock, flags);
> >>> +out:
> >>> +	kfree(log);
> >>> +}
> >>> +
> >>>    static void nvme_fw_act_work(struct work_struct *work)
> >>>    {
> >>>    	struct nvme_ctrl *ctrl = container_of(work,
> >>> @@ -4949,6 +4991,9 @@ static bool nvme_handle_aen_notice(struct nvme_ctrl *ctrl, u32 result)
> >>>    	case NVME_AER_NOTICE_DISC_CHANGED:
> >>>    		ctrl->aen_result = result;
> >>>    		break;
> >>> +	case NVME_AER_NOTICE_CCR_COMPLETED:
> >>> +		queue_work(nvme_wq, &ctrl->ccr_work);
> >>> +		break;
> >>>    	default:
> >>>    		dev_warn(ctrl->device, "async event result %08x\n", result);
> >>>    	}
> >>> @@ -5144,6 +5189,7 @@ void nvme_stop_ctrl(struct nvme_ctrl *ctrl)
> >>>    	nvme_stop_failfast_work(ctrl);
> >>>    	flush_work(&ctrl->async_event_work);
> >>>    	cancel_work_sync(&ctrl->fw_act_work);
> >>> +	cancel_work_sync(&ctrl->ccr_work);
> >>>    	if (ctrl->ops->stop_ctrl)
> >>>    		ctrl->ops->stop_ctrl(ctrl);
> >>>    }
> >>> @@ -5267,6 +5313,7 @@ int nvme_init_ctrl(struct nvme_ctrl *ctrl, struct device *dev,
> >>>    	ctrl->quirks = quirks;
> >>>    	ctrl->numa_node = NUMA_NO_NODE;
> >>>    	INIT_WORK(&ctrl->scan_work, nvme_scan_work);
> >>> +	INIT_WORK(&ctrl->ccr_work, nvme_ccr_work);
> >>>    	INIT_WORK(&ctrl->async_event_work, nvme_async_event_work);
> >>>    	INIT_WORK(&ctrl->fw_act_work, nvme_fw_act_work);
> >>>    	INIT_WORK(&ctrl->delete_work, nvme_delete_ctrl_work);
> >>> diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h
> >>> index f2bcff9ccd25..776ee8aa5a93 100644
> >>> --- a/drivers/nvme/host/nvme.h
> >>> +++ b/drivers/nvme/host/nvme.h
> >>> @@ -419,6 +419,7 @@ struct nvme_ctrl {
> >>>    	struct nvme_effects_log *effects;
> >>>    	struct xarray cels;
> >>>    	struct work_struct scan_work;
> >>> +	struct work_struct ccr_work;
> >>>    	struct work_struct async_event_work;
> >>>    	struct delayed_work ka_work;
> >>>    	struct delayed_work failfast_work;
> >>
> >> Hmm. The 'nvme_fence_ctrl' operation introduced in the previous patch
> >> is synchronous, yet in this patch we're looking a a log page to figure
> >> out if the cross-controller reset is complete.
> >> Which is slightly irritating.
> >> Wouldn't it be better to make the 'nvme_fence_ctrl' operation
> >> asynchronous, and then have a separate function to wait for the fence
> >> operation to complete (which then could look at log pages etc)?
> > 
> > True nvme_fence_ctrl() is synchronous, but it runs in from ctrl->fencing_work.
> > What is it that you find irritating about nvme_fence_ctrl()?
> > 
> 
> Thins is, in order to make nvme_fence_ctrl() synchronous we have to
> wait for the operation itself (which is asynchronous) to complete.
> And that wait in itself is implemented by a wait queue.
> So we're having a wait queue calling nvme_fence_ctrl(), which calls
> another wait queue waiting for a completion.
> And then (if the IRS bit is not set) calling another waitqueue for
> checking the log page.

There is no point of checking the CCR logpage before getting AEN. Sure
we can implement some sort of polling, but I do not think this is the
right approach.

> 
> I think we could simplify this by simply making nvme_fence_ctrl() 
> asynchronous, which could do away with all the workqueue handling.

I am not sure I understand exactly how nvme_fence_ctrl() can be make
asynchronous. Can you provide example code?