virtio/vhost-scsi: fix virtio-scsi/vhost-scsi child refcount in transports

object_initialize() leaves the object with a refcount of 1.
object_property_add_child() adds its own reference which is dropped
again when the property is deleted.

The upshot of this is that we always have a refcount >= 1.  Upon hot
unplug the virtio-scsi/vhost-scsi child is not finalized!

Drop our reference after the child property has been added to the
parent.
Signed-off-by: NGonglei <arei.gonglei@huawei.com>
Reviewed-by: NCornelia Huck <cornelia.huck@de.ibm.com>
Cc: qemu-stable@nongnu.org
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

hw/s390x/s390-virtio-bus.c

@@ -258,6 +258,7 @@ static void s390_virtio_scsi_instance_init(Object *obj)
     VirtIOSCSIS390 *dev = VIRTIO_SCSI_S390(obj);
     object_initialize(&dev->vdev, sizeof(dev->vdev), TYPE_VIRTIO_SCSI);
     object_property_add_child(obj, "virtio-backend", OBJECT(&dev->vdev), NULL);
+    object_unref(OBJECT(&dev->vdev));
     qdev_alias_all_properties(DEVICE(&dev->vdev), obj);
 }
 
@@ -280,6 +281,7 @@ static void s390_vhost_scsi_instance_init(Object *obj)
     VHostSCSIS390 *dev = VHOST_SCSI_S390(obj);
     object_initialize(&dev->vdev, sizeof(dev->vdev), TYPE_VHOST_SCSI);
     object_property_add_child(obj, "virtio-backend", OBJECT(&dev->vdev), NULL);
+    object_unref(OBJECT(&dev->vdev));
     qdev_alias_all_properties(DEVICE(&dev->vdev), obj);
 }
 #endif

hw/s390x/virtio-ccw.c

@@ -938,6 +938,7 @@ static void virtio_ccw_scsi_instance_init(Object *obj)
     VirtIOSCSICcw *dev = VIRTIO_SCSI_CCW(obj);
     object_initialize(&dev->vdev, sizeof(dev->vdev), TYPE_VIRTIO_SCSI);
     object_property_add_child(obj, "virtio-backend", OBJECT(&dev->vdev), NULL);
+    object_unref(OBJECT(&dev->vdev));
     qdev_alias_all_properties(DEVICE(&dev->vdev), obj);
 }
 
@@ -960,6 +961,7 @@ static void vhost_ccw_scsi_instance_init(Object *obj)
     VHostSCSICcw *dev = VHOST_SCSI_CCW(obj);
     object_initialize(&dev->vdev, sizeof(dev->vdev), TYPE_VHOST_SCSI);
     object_property_add_child(obj, "virtio-backend", OBJECT(&dev->vdev), NULL);
+    object_unref(OBJECT(&dev->vdev));
     qdev_alias_all_properties(DEVICE(&dev->vdev), obj);
 }
 #endif

hw/virtio/virtio-pci.c

@@ -1186,6 +1186,7 @@ static void virtio_scsi_pci_instance_init(Object *obj)
     VirtIOSCSIPCI *dev = VIRTIO_SCSI_PCI(obj);
     object_initialize(&dev->vdev, sizeof(dev->vdev), TYPE_VIRTIO_SCSI);
     object_property_add_child(obj, "virtio-backend", OBJECT(&dev->vdev), NULL);
+    object_unref(OBJECT(&dev->vdev));
     qdev_alias_all_properties(DEVICE(&dev->vdev), obj);
 }
 
@@ -1242,6 +1243,7 @@ static void vhost_scsi_pci_instance_init(Object *obj)
     VHostSCSIPCI *dev = VHOST_SCSI_PCI(obj);
     object_initialize(&dev->vdev, sizeof(dev->vdev), TYPE_VHOST_SCSI);
     object_property_add_child(obj, "virtio-backend", OBJECT(&dev->vdev), NULL);
+    object_unref(OBJECT(&dev->vdev));
     qdev_alias_all_properties(DEVICE(&dev->vdev), obj);
 }