NVMe: Short-cut removal on surprise hot-unplug

This patch adds a new state that when set has the core automatically
kill request queues prior to removing namespaces.

If PCI device is not present at the time the nvme driver's remove is
called, we can kill all IO queues immediately instead of waiting for
the watchdog thread to do that at its polling interval. This improves
scenarios where multiple hot plug events occur at the same time since
it doesn't block the pci enumeration for as long.

Signed-off-by: Keith Busch <keith.busch@intel.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@fb.com>

drivers/nvme/host/core.c

@@ -95,6 +95,15 @@ bool nvme_change_ctrl_state(struct nvme_ctrl *ctrl,
 			break;
 		}
 		break;
+	case NVME_CTRL_DEAD:
+		switch (old_state) {
+		case NVME_CTRL_DELETING:
+			changed = true;
+			/* FALLTHRU */
+		default:
+			break;
+		}
+		break;
 	default:
 		break;
 	}
@@ -1595,6 +1604,15 @@ void nvme_remove_namespaces(struct nvme_ctrl *ctrl)
 {
 	struct nvme_ns *ns, *next;
 
+	/*
+	 * The dead states indicates the controller was not gracefully
+	 * disconnected. In that case, we won't be able to flush any data while
+	 * removing the namespaces' disks; fail all the queues now to avoid
+	 * potentially having to clean up the failed sync later.
+	 */
+	if (ctrl->state == NVME_CTRL_DEAD)
+		nvme_kill_queues(ctrl);
+
 	mutex_lock(&ctrl->namespaces_mutex);
 	list_for_each_entry_safe(ns, next, &ctrl->namespaces, list)
 		nvme_ns_remove(ns);

drivers/nvme/host/nvme.h

@@ -72,6 +72,7 @@ enum nvme_ctrl_state {
 	NVME_CTRL_LIVE,
 	NVME_CTRL_RESETTING,
 	NVME_CTRL_DELETING,
+	NVME_CTRL_DEAD,
 };
 
 struct nvme_ctrl {

drivers/nvme/host/pci.c

@@ -2017,6 +2017,10 @@ static void nvme_remove(struct pci_dev *pdev)
 	nvme_change_ctrl_state(&dev->ctrl, NVME_CTRL_DELETING);
 
 	pci_set_drvdata(pdev, NULL);
+
+	if (!pci_device_is_present(pdev))
+		nvme_change_ctrl_state(&dev->ctrl, NVME_CTRL_DEAD);
+
 	flush_work(&dev->reset_work);
 	nvme_uninit_ctrl(&dev->ctrl);
 	nvme_dev_disable(dev, true);