installer: fix the "umount: XXX not mounted" error message during postinst

chromeos-setimage

 #!/bin/sh -u
 # Copyright (c) 2010 The Chromium OS Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 #
 # A script to display or change the preferred image
 
 # Load functions and constants for chromeos-install.
 . "$(dirname "$0")/chromeos-common.sh" || exit 1
 if [ -e /usr/lib/shflags ]; then
@@ skipping 95 matching lines @@
   echo "Error: Unable to find block device: $FLAGS_dst"
   exit 1
 fi
 
 # Setup loop devices so that we don't get burned by the kernel not knowing
 # about updated partition changes.
 ESP_LOOP=
 ROOT_LOOP=
 KERN_LOOP=
 
+# Cleans up a device and unmount if required.
 cleanup_loop() {
   local dev="$1"
-  if [ -z "$dev" ]; then
+  local need_umount="$2"
+  if [ -z "${dev}" ]; then
     return 0
   fi
-  (sudo umount "$dev" || true)
-  (sudo losetup -d "$dev" || true)
+  if [ ${need_umount} -eq ${FLAGS_TRUE} ]; then
+    sudo umount -d "${dev}" || true
+  elif [ ${need_umount} -eq ${FLAGS_FALSE} ]; then
+    sudo losetup -d "${dev}" || true
+  else
+    echo "INTERNAL ERROR: unknown parameter for cleanup_loop: ${need_umount}" >&2
+  fi
 }
 
 cleanup() {
-  cleanup_loop "${ESP_LOOP}"
+  # Currently only ESP may be mounted. KERN and ROOT are never mounted.
+  cleanup_loop "${ESP_LOOP}" "${FLAGS_TRUE}"
   ESP_LOOP=
-  cleanup_loop "${KERN_LOOP}"
+  cleanup_loop "${KERN_LOOP}" "${FLAGS_FALSE}"
   KERN_LOOP=
-  cleanup_loop "${ROOT_LOOP}"
+  cleanup_loop "${ROOT_LOOP}" "${FLAGS_FALSE}"
   ROOT_LOOP=
 
   # Failing to clean this up isn't the worst.
   if [ -n "${ESP_TMP_DIR}" ]; then
     rmdir "${ESP_TMP_DIR}" || true
   fi
 
   rm -f ${tempfile} || true
 }
 
@@ skipping 211 matching lines @@
 grep -qs '^set default=3' ${mountpoint}/efi/boot/grub.cfg && echo "B (verified)"
 
 echo "Current legacy boot default is:"
 # Print the [new] default choice
 grep -qs 's-hd\.A$' ${mountpoint}/syslinux/default.cfg && echo "A"
 grep -qs 's-hd\.B$' ${mountpoint}/syslinux/default.cfg && echo "B"
 grep -qs 'vhd\.A$' ${mountpoint}/syslinux/default.cfg && echo "A (verified)"
 grep -qs 'vhd\.B$' ${mountpoint}/syslinux/default.cfg && echo "B (verified)"
 
 exit $EXIT_CODE