Re: [PATCH 5/9] nvme: track subsystems

[Sagi Grimberg]

@@ -2230,7 +2315,7 @@ static ssize_t nvme_sysfs_show_subsysnqn(struct device 
*dev,
  {
        struct nvme_ctrl *ctrl = dev_get_drvdata(dev);

- return snprintf(buf, PAGE_SIZE, "%s\n", ctrl->subnqn);

+       return snprintf(buf, PAGE_SIZE, "%s\n", ctrl->subsys->subnqn);
  }
  static DEVICE_ATTR(subsysnqn, S_IRUGO, nvme_sysfs_show_subsysnqn, NULL);

@@ -2770,12 +2855,22 @@ EXPORT_SYMBOL_GPL(nvme_uninit_ctrl);

  static void nvme_free_ctrl(struct kref *kref)
  {
        struct nvme_ctrl *ctrl = container_of(kref, struct nvme_ctrl, kref);
+       struct nvme_subsystem *subsys = ctrl->subsys;

put_device(ctrl->device);

        nvme_release_instance(ctrl);
        ida_destroy(&ctrl->ns_ida);

+ if (subsys) {

+               mutex_lock(&subsys->lock);
+               list_del(&ctrl->subsys_entry);
+               mutex_unlock(&subsys->lock);
+       }
+

When can this happen? can a controller not have a subsys?