Always use new_size when extend

Always use new_size when extend.
Closes-Bug: #1909951

Change-Id: Ic5faa887448f363bb4d91bccfe8e035a06936454

manila/share/drivers/generic.py

@@ -667,7 +667,7 @@ class GenericShareDriver(driver.ExecuteMixin, driver.ShareDriver):
                 server_details['instance_id'],
                 volume)
 
-        self._resize_filesystem(server_details, volume)
+        self._resize_filesystem(server_details, volume, new_size=new_size)
         self._mount_device(share, server_details, volume)
         helper.restore_access_after_maintenance(server_details,
                                                 share['name'])

releasenotes/notes/bug-1909951-fix-extend-have-wrong-size-7938eaa6591bd2ad.yaml

@@ -0,0 +1,7 @@
+---
+fixes:
+  - |
+    Fixed a bug that if extend a volume after shrink it under generic
+    driver, it may have a wrong real size. Please see
+    `Launchpad bug <https://bugs.launchpad.net/manila/+bug/1909951>`_
+    for more details.