Abstract cleanups in a CLEANUP array

Rather than just having two cleanups for the whole script (namely the
umounting and removal of the temp directory) we can change cleanups with
an array structure, which is then executed in reverse order. This will
be used to add more operations that need their own cleanup, in a
structured way.

Reviewed-by: iustinp

diff --git a/create.in b/create.in
index e34c719..7840789 100755 (executable)
--- a/create.in
+++ b/create.in
@@ -19,6 +19,20 @@
 
 set -e
 
+CLEANUP=( )
+
+cleanup() {
+  if [ ${#CLEANUP[*]} -gt 0 ]; then
+    LAST_ELEMENT=$((${#CLEANUP[*]}-1))
+    REVERSE_INDEXES=$(seq ${LAST_ELEMENT} -1 0)
+    for i in $REVERSE_INDEXES; do
+      ${CLEANUP[$i]}
+    done
+  fi
+}
+
+trap cleanup EXIT
+
 DEFAULT_FILE="@sysconfdir@/default/ganeti-instance-debootstrap"
 if [ -f "$DEFAULT_FILE" ]; then
     . "$DEFAULT_FILE"
@@ -56,7 +70,7 @@ if [ -n "$swapdev" ]; then
 fi
 
 TMPDIR=`mktemp -d` || exit 1
-trap "umount $TMPDIR; rmdir $TMPDIR" EXIT
+CLEANUP+=("rmdir $TMPDIR")
 
 # If it's not a block device try to mount it via loopback device.
 # This is needed for file disks.
@@ -65,6 +79,7 @@ if [ ! -b $blockdev ]; then
   MOUNT_OPTIONS="$MOUNT_OPTIONS -o loop"
 fi
 mount $MOUNT_OPTIONS $blockdev $TMPDIR
+CLEANUP+=("umount $TMPDIR")
 
 # remove the cache file if it's old (> 2 weeks) and writable by the owner (the
 # default due to the standard umask)
@@ -135,8 +150,8 @@ elif [ -e $TMPDIR/etc/event.d/tty1 ]; then
   rm $TMPDIR/etc/event.d/tty1
 fi
 
-umount $TMPDIR
-rmdir $TMPDIR
+# execute cleanups
+cleanup
 trap - EXIT
 
 exit 0