nvme: only add a controller to dev_list after it's been fully initialized

Without this we can easily get bad derferences on nvmeq->d_db when the nvme
kthread tries to poll the CQs for controllers that are in half initialized
state.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NKeith Busch <keith.busch@intel.com>
Signed-off-by: NJens Axboe <axboe@fb.com>

drivers/nvme/host/pci.c

@@ -1994,6 +1994,30 @@ static void nvme_disable_io_queues(struct nvme_dev *dev)
 	kthread_stop(kworker_task);
 }
 
+static int nvme_dev_list_add(struct nvme_dev *dev)
+{
+	bool start_thread = false;
+
+	spin_lock(&dev_list_lock);
+	if (list_empty(&dev_list) && IS_ERR_OR_NULL(nvme_thread)) {
+		start_thread = true;
+		nvme_thread = NULL;
+	}
+	list_add(&dev->node, &dev_list);
+	spin_unlock(&dev_list_lock);
+
+	if (start_thread) {
+		nvme_thread = kthread_run(nvme_kthread, NULL, "nvme");
+		wake_up_all(&nvme_kthread_wait);
+	} else
+		wait_event_killable(nvme_kthread_wait, nvme_thread);
+
+	if (IS_ERR_OR_NULL(nvme_thread))
+		return nvme_thread ? PTR_ERR(nvme_thread) : -EINTR;
+
+	return 0;
+}
+
 /*
 * Remove the node from the device list and check
 * for whether or not we need to stop the nvme_thread.
@@ -2109,7 +2133,6 @@ static void nvme_pci_free_ctrl(struct nvme_ctrl *ctrl)
 static void nvme_probe_work(struct work_struct *work)
 {
 	struct nvme_dev *dev = container_of(work, struct nvme_dev, probe_work);
-	bool start_thread = false;
 	int result;
 
 	result = nvme_dev_map(dev);
@@ -2120,25 +2143,6 @@ static void nvme_probe_work(struct work_struct *work)
 	if (result)
 		goto unmap;
 
-	spin_lock(&dev_list_lock);
-	if (list_empty(&dev_list) && IS_ERR_OR_NULL(nvme_thread)) {
-		start_thread = true;
-		nvme_thread = NULL;
-	}
-	list_add(&dev->node, &dev_list);
-	spin_unlock(&dev_list_lock);
-
-	if (start_thread) {
-		nvme_thread = kthread_run(nvme_kthread, NULL, "nvme");
-		wake_up_all(&nvme_kthread_wait);
-	} else
-		wait_event_killable(nvme_kthread_wait, nvme_thread);
-
-	if (IS_ERR_OR_NULL(nvme_thread)) {
-		result = nvme_thread ? PTR_ERR(nvme_thread) : -EINTR;
-		goto disable;
-	}
-
 	nvme_init_queue(dev->queues[0], 0);
 	result = nvme_alloc_admin_tags(dev);
 	if (result)
@@ -2154,6 +2158,10 @@ static void nvme_probe_work(struct work_struct *work)
 
 	dev->ctrl.event_limit = 1;
 
+	result = nvme_dev_list_add(dev);
+	if (result)
+		goto remove;
+
 	/*
 	 * Keep the controller around but remove all namespaces if we don't have
 	 * any working I/O queue.
@@ -2168,6 +2176,8 @@ static void nvme_probe_work(struct work_struct *work)
 
 	return;
 
+ remove:
+	nvme_dev_list_remove(dev);
  free_tags:
 	nvme_dev_remove_admin(dev);
 	blk_put_queue(dev->ctrl.admin_q);
@@ -2175,7 +2185,6 @@ static void nvme_probe_work(struct work_struct *work)
 	dev->queues[0]->tags = NULL;
  disable:
 	nvme_disable_queue(dev, 0);
-	nvme_dev_list_remove(dev);
  unmap:
 	nvme_dev_unmap(dev);
  out: