common: make safe_umount retry a few times

on Fedora 18 on Gnome 3.0 something is making the first attempt at
unmounting return busy. Unfortunatly, the return code is 32 everytime
so we have to parse the output of umount :( :( :(

Change-Id: I7f94bf6c2059c7e7cb4fb173d9ffbabd59f2b24f

bin/cros_update_image.sh

@@ -66,10 +66,10 @@ if [[ ${PKGS/kernel/} != ${PKGS} ]]; then
    sudo dd if="./rootfs/boot/vmlinuz" of=part_2 bs=512 count=8192 conv=notrunc
 fi
 
-sudo umount rootfs/usr/local
-sudo umount rootfs/var
-sudo umount rootfs
-sudo umount stateful_part
+safe_umount rootfs/usr/local
+safe_umount rootfs/var
+safe_umount rootfs
+safe_umount stateful_part
 ./pack_partitions.sh ${IMAGE}
 
 cd -

build_library/disk_layout_util.sh

@@ -64,7 +64,7 @@ run_partition_script() {
   sudo mount -o loop "${root_fs_img}" "${root_fs_dir}"
   . "${root_fs_dir}/${PARTITION_SCRIPT_PATH}"
   write_partition_table "${outdev}" "${pmbr_img}"
-  sudo umount "${root_fs_dir}"
+  safe_umount "${root_fs_dir}"
 }
 
 get_fs_block_size() {

common.sh

@@ -705,7 +705,33 @@ safe_umount_tree() {
 
 # Run umount as root.
 safe_umount() {
-  $([[ ${UID:-$(id -u)} != 0 ]] && echo sudo) umount "$@"
+  local ret=0
+  local out=""
+  set +e
+  for i in $(seq 1 4); do
+    out=`$([[ ${UID:-$(id -u)} != 0 ]] && echo sudo) umount "$@" 2>&1`
+    ret=$?
+    if [[ $ret -eq 0 ]]; then
+      set -e
+      return 0
+    fi
+    # Mount is not found
+    if [[ `expr index "${out}" "not found"` -ne "0" ]]; then
+      set -e
+      return 0
+    fi
+    # Mount is not mounted.
+    if [[ `expr index "${out}" "not mounted"` -ne "0" ]]; then
+      set -e
+      return 0
+    fi
+    sleep 1
+    # Mount is actually busy.
+    if [[ `expr index "${out}" "busy"` -ne "0" ]]; then
+      continue
+    fi
+  done
+  return $ret
 }
 
 get_git_id() {