image_copy: support compressed images

This patch adds support for compressed images in the image_copy test.
This reduces the time for the image copy from around three minutes to
less than one minute (over Gigabit Ethernet).

gzip and xz are supported.  xz produces smaller images but needs more
cpu time for decompressing.  In my setup gzip is limited by network
bandwidth whereas xz is limited by cpu speed.  In the end both are
almost on par speed-wise, with gzip being a little bit faster.
Signed-off-by: NGerd Hoffmann <kraxel@redhat.com>

tests/image_copy.py

@@ -31,15 +31,22 @@ def run_image_copy(test, params, env):
                        params['image_format'])
     src_path = os.path.join(mount_dest_dir, image)
     dst_path = '%s/%s.%s' % (data_dir.get_data_dir(), params['image_name'], params['image_format'])
-    cmd = 'cp %s %s' % (src_path, dst_path)
 
     if not utils_misc.mount(src, mount_dest_dir, 'nfs', 'ro'):
         raise error.TestError('Could not mount NFS share %s to %s' %
                               (src, mount_dest_dir))
 
     # Check the existence of source image
-    if not os.path.exists(src_path):
+    if os.path.exists("%s.xz" % src_path):
+        logging.debug('Copying image %s (from xz) ...', image)
+        cmd = "xz -cd %s.xz > %s" % (src_path, dst_path)
+    elif os.path.exists("%s.gz" % src_path):
+        logging.debug('Copying image %s (from gzip) ...', image)
+        cmd = "gzip -cd %s.gz > %s" % (src_path, dst_path)
+    elif os.path.exists(src_path):
+        logging.debug('Copying image %s (uncompressed) ...', image)
+        cmd = 'cp %s %s' % (src_path, dst_path)
+    else:
         raise error.TestError('Could not find %s in NFS share' % src_path)
 
-    logging.debug('Copying image %s...', image)
     utils.system(cmd)