nvme-hwmon: rework to avoid devm allocation

The original design to use device-managed resource allocation
doesn't really work as the NVMe controller has a vastly different
lifetime than the hwmon sysfs attributes, causing warning about
duplicate sysfs entries upon reconnection.
This patch reworks the hwmon allocation to avoid device-managed
resource allocation, and uses the NVMe controller as parent for
the sysfs attributes.

Cc: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Hannes Reinecke <hare@suse.de>
Tested-by: Enzo Matsumiya <ematsumiya@suse.de>
Tested-by: Daniel Wagner <dwagner@suse.de>
Signed-off-by: Christoph Hellwig <hch@lst.de>

drivers/nvme/host/core.c

@@ -4471,6 +4471,7 @@ EXPORT_SYMBOL_GPL(nvme_start_ctrl);
 
 void nvme_uninit_ctrl(struct nvme_ctrl *ctrl)
 {
+	nvme_hwmon_exit(ctrl);
 	nvme_fault_inject_fini(&ctrl->fault_inject);
 	dev_pm_qos_hide_latency_tolerance(ctrl->device);
 	cdev_device_del(&ctrl->cdev, ctrl->device);

drivers/nvme/host/hwmon.c

@@ -223,12 +223,12 @@ static const struct hwmon_chip_info nvme_hwmon_chip_info = {
 
 int nvme_hwmon_init(struct nvme_ctrl *ctrl)
 {
-	struct device *dev = ctrl->dev;
+	struct device *dev = ctrl->device;
 	struct nvme_hwmon_data *data;
 	struct device *hwmon;
 	int err;
 
-	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
+	data = kzalloc(sizeof(*data), GFP_KERNEL);
 	if (!data)
 		return 0;
 
@@ -237,19 +237,30 @@ int nvme_hwmon_init(struct nvme_ctrl *ctrl)
 
 	err = nvme_hwmon_get_smart_log(data);
 	if (err) {
-		dev_warn(ctrl->device,
-			"Failed to read smart log (error %d)\n", err);
-		devm_kfree(dev, data);
+		dev_warn(dev, "Failed to read smart log (error %d)\n", err);
+		kfree(data);
 		return err;
 	}
 
-	hwmon = devm_hwmon_device_register_with_info(dev, "nvme", data,
-						     &nvme_hwmon_chip_info,
-						     NULL);
+	hwmon = hwmon_device_register_with_info(dev, "nvme",
+						data, &nvme_hwmon_chip_info,
+						NULL);
 	if (IS_ERR(hwmon)) {
 		dev_warn(dev, "Failed to instantiate hwmon device\n");
-		devm_kfree(dev, data);
+		kfree(data);
 	}
-
+	ctrl->hwmon_device = hwmon;
 	return 0;
 }
+
+void nvme_hwmon_exit(struct nvme_ctrl *ctrl)
+{
+	if (ctrl->hwmon_device) {
+		struct nvme_hwmon_data *data =
+			dev_get_drvdata(ctrl->hwmon_device);
+
+		hwmon_device_unregister(ctrl->hwmon_device);
+		ctrl->hwmon_device = NULL;
+		kfree(data);
+	}
+}

drivers/nvme/host/nvme.h

@@ -246,6 +246,9 @@ struct nvme_ctrl {
 	struct rw_semaphore namespaces_rwsem;
 	struct device ctrl_device;
 	struct device *device;	/* char device */
+#ifdef CONFIG_NVME_HWMON
+	struct device *hwmon_device;
+#endif
 	struct cdev cdev;
 	struct work_struct reset_work;
 	struct work_struct delete_work;
@@ -812,11 +815,16 @@ static inline struct nvme_ns *nvme_get_ns_from_dev(struct device *dev)
 
 #ifdef CONFIG_NVME_HWMON
 int nvme_hwmon_init(struct nvme_ctrl *ctrl);
+void nvme_hwmon_exit(struct nvme_ctrl *ctrl);
 #else
 static inline int nvme_hwmon_init(struct nvme_ctrl *ctrl)
 {
 	return 0;
 }
+
+static inline void nvme_hwmon_exit(struct nvme_ctrl *ctrl)
+{
+}
 #endif
 
 u32 nvme_command_effects(struct nvme_ctrl *ctrl, struct nvme_ns *ns,