From 75a63613bcd76282e86b40fab2356a6e7b5a540b Mon Sep 17 00:00:00 2001
From: Marek Marczykowski <marmarek@invisiblethingslab.com>
Date: Sun, 28 Apr 2013 22:38:40 +0200
Subject: [PATCH] cleanup-image: smart image shrink using fstrim

Linux loop driver support TRIM operation for some time (from 3.1
kernel), which is mapped to hole punch operation in underlying
filesystem (which must support it - ext* and xfs have it).
This is much faster and less space consuming than previous cp --sparse
method.
---
 cleanup_image | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/cleanup_image b/cleanup_image
index 522d9d4..3716593 100755
--- a/cleanup_image
+++ b/cleanup_image
@@ -23,11 +23,7 @@ export INSTALLDIR=`pwd`/mnt/
 $SCRIPTSDIR/09_cleanup.sh
 
 echo "--> Compacting image file..."
-dd if=/dev/zero of=mnt/fillme bs=1M > /dev/null 2>&1 || true
-sync
-rm mnt/fillme
+fstrim mnt/
 umount mnt
-cp --sparse=always $IMG $IMG.new
-mv  $IMG.new $IMG
 ls -als $IMG