btrfs: fix the allocated size

build_library/build_image_util.sh

@@ -806,6 +806,8 @@ EOF
     sudo fstrim "${root_fs_dir}/usr" || true
   fi
 
+  "${BUILD_LIBRARY_DIR}/disk_util" --disk_layout="${disk_layout}" btrfsresetallocation \
+      "${root_fs_dir}/usr"
   # Make the filesystem un-mountable as read-write and setup verity.
   if [[ ${disable_read_write} -eq ${FLAGS_TRUE} ]]; then
     # Unmount /usr partition

build_library/disk_util

@@ -768,6 +768,25 @@ def Tune(options):
   if not action_done:
     raise Exception("No options specified!")
 
+def SudoOutputToConsole(cmd):
+  print(SudoOutput(cmd).decode())
+
+def LogBtrfsUsage(mount_point, section=None):
+  print('Btrfs usage for mount point `%s` %s' % (mount_point, section))
+  try:
+      SudoOutputToConsole(['btrfs', 'fi', 'usage', mount_point])
+  except Exception as ex:
+      print('Btrfs usage could not be retrieved for mount point `%s` %s' % (mount_point, section))
+      print(ex)
+
+def BtrfsResetAllocation(options):
+
+    LogBtrfsUsage(options.disk_image, 'before disk resize')
+    try:
+        Sudo(['btrfs', 'fi', 'resize', '-500m', options.disk_image])
+    except Exception as ex:
+        print(ex)
+    LogBtrfsUsage(options.disk_image, 'after disk resize')
 
 def Verity(options):
   """Hash verity protected filesystems.
@@ -1119,6 +1138,10 @@ def main(argv):
   a = actions.add_parser('parseonly', help='validate config')
   a.set_defaults(func=DoParseOnly)
 
+  a = actions.add_parser('btrfsresetallocation', help='btrfs reset allocation')
+  a.add_argument('disk_image', help='path to disk image file')
+  a.set_defaults(func=BtrfsResetAllocation)
+
   options = parser.parse_args(argv[1:])
   options.func(options)