utils_libvirt/libvirt_disk: add function to discover new disk

As the disk names like /dev/sda /dev/vda are unstable between boots,
Detect new disks inside a VM (e.g. after a coldplug) as the ones
that are not used.

Signed-off-by: Sebastian Mitterle <[email protected]>

virttest/utils_libvirt/libvirt_disk.py

@@ -24,6 +24,37 @@
 LOG = logging.getLogger('avocado.' + __name__)
 
 
+def get_new_disk(session):
+    """
+    Identifies the single disk below /dev/
+    that's not mounted currently.
+
+    :param session: VM session
+    :param test: Test instance
+    :return path: absolute path of disk
+                  e.g. /dev/sda
+    """
+    cmd = "lsblk -n -p -l -o NAME,MOUNTPOINT"
+    s, o = utils_misc.cmd_status_output(cmd,
+                                        ignore_status=False,
+                                        shell=True,
+                                        verbose=True,
+                                        session=session)
+    if s:
+        raise exceptions.TestError("Couldn't determine the new disk: '%s'" % o)
+    current = None
+    lines = o.split("\n")
+    for line in lines:
+        if re.search(r'^/dev/[a-z]+\s+$', line):
+            current = line
+            if lines.index(line) == len(lines) - 1:
+                break
+        if current and current in line:
+            continue
+    logging.debug("Identified '%s' in '%s'", current.strip(), o)
+    return current.strip()
+
+
 def create_disk(disk_type, path=None, size="500M", disk_format="raw", extra='',
                 session=None):
     """