vduse: Tie vduse mgmtdev and its device

[ Upstream commit 0e0348ac3f ]

vduse devices are not backed by any real devices such as PCI. Hence it
doesn't have any parent device linked to it.

Kernel driver model in [1] suggests to avoid an empty device
release callback.

Hence tie the mgmtdevice object's life cycle to an allocate dummy struct
device instead of static one.

[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/core-api/kobject.rst?h=v5.18-rc7#n284

Signed-off-by: Parav Pandit <parav@nvidia.com>
Message-Id: <20220613195223.473966-1-parav@nvidia.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Xie Yongji <xieyongji@bytedance.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

drivers/vdpa/vdpa_user/vduse_dev.c

@@ -1466,16 +1466,12 @@ static char *vduse_devnode(struct device *dev, umode_t *mode)
 	return kasprintf(GFP_KERNEL, "vduse/%s", dev_name(dev));
 }
 
-static void vduse_mgmtdev_release(struct device *dev)
-{
-}
-
-static struct device vduse_mgmtdev = {
-	.init_name = "vduse",
-	.release = vduse_mgmtdev_release,
+struct vduse_mgmt_dev {
+	struct vdpa_mgmt_dev mgmt_dev;
+	struct device dev;
 };
 
-static struct vdpa_mgmt_dev mgmt_dev;
+static struct vduse_mgmt_dev *vduse_mgmt;
 
 static int vduse_dev_init_vdpa(struct vduse_dev *dev, const char *name)
 {
@@ -1500,7 +1496,7 @@ static int vduse_dev_init_vdpa(struct vduse_dev *dev, const char *name)
 	}
 	set_dma_ops(&vdev->vdpa.dev, &vduse_dev_dma_ops);
 	vdev->vdpa.dma_dev = &vdev->vdpa.dev;
-	vdev->vdpa.mdev = &mgmt_dev;
+	vdev->vdpa.mdev = &vduse_mgmt->mgmt_dev;
 
 	return 0;
 }
@@ -1545,34 +1541,52 @@ static struct virtio_device_id id_table[] = {
 	{ 0 },
 };
 
-static struct vdpa_mgmt_dev mgmt_dev = {
-	.device = &vduse_mgmtdev,
-	.id_table = id_table,
-	.ops = &vdpa_dev_mgmtdev_ops,
-};
+static void vduse_mgmtdev_release(struct device *dev)
+{
+	struct vduse_mgmt_dev *mgmt_dev;
+
+	mgmt_dev = container_of(dev, struct vduse_mgmt_dev, dev);
+	kfree(mgmt_dev);
+}
 
 static int vduse_mgmtdev_init(void)
 {
 	int ret;
 
-	ret = device_register(&vduse_mgmtdev);
-	if (ret)
+	vduse_mgmt = kzalloc(sizeof(*vduse_mgmt), GFP_KERNEL);
+	if (!vduse_mgmt)
+		return -ENOMEM;
+
+	ret = dev_set_name(&vduse_mgmt->dev, "vduse");
+	if (ret) {
+		kfree(vduse_mgmt);
 		return ret;
+	}
 
-	ret = vdpa_mgmtdev_register(&mgmt_dev);
+	vduse_mgmt->dev.release = vduse_mgmtdev_release;
+
+	ret = device_register(&vduse_mgmt->dev);
 	if (ret)
-		goto err;
+		goto dev_reg_err;
 
-	return 0;
-err:
-	device_unregister(&vduse_mgmtdev);
+	vduse_mgmt->mgmt_dev.id_table = id_table;
+	vduse_mgmt->mgmt_dev.ops = &vdpa_dev_mgmtdev_ops;
+	vduse_mgmt->mgmt_dev.device = &vduse_mgmt->dev;
+	ret = vdpa_mgmtdev_register(&vduse_mgmt->mgmt_dev);
+	if (ret)
+		device_unregister(&vduse_mgmt->dev);
+
+	return ret;
+
+dev_reg_err:
+	put_device(&vduse_mgmt->dev);
 	return ret;
 }
 
 static void vduse_mgmtdev_exit(void)
 {
-	vdpa_mgmtdev_unregister(&mgmt_dev);
-	device_unregister(&vduse_mgmtdev);
+	vdpa_mgmtdev_unregister(&vduse_mgmt->mgmt_dev);
+	device_unregister(&vduse_mgmt->dev);
 }
 
 static int vduse_init(void)