1 files changed, 88 insertions, 0 deletions
diff --git a/charms/trusty/ceilometer/charmhelpers/contrib/storage/linux/loopback.py b/charms/trusty/ceilometer/charmhelpers/contrib/storage/linux/loopback.py
new file mode 100644
index 0000000..3a3f514
--- /dev/null
+++ b/charms/trusty/ceilometer/charmhelpers/contrib/storage/linux/loopback.py
@@ -0,0 +1,88 @@
+# Copyright 2014-2015 Canonical Limited.
+#
+# This file is part of charm-helpers.
+#
+# charm-helpers is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Lesser General Public License version 3 as
+# published by the Free Software Foundation.
+#
+# charm-helpers is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public License
+# along with charm-helpers.  If not, see <http://www.gnu.org/licenses/>.
+
+import os
+import re
+from subprocess import (
+    check_call,
+    check_output,
+)
+
+import six
+
+
+##################################################
+# loopback device helpers.
+##################################################
+def loopback_devices():
+    '''
+    Parse through 'losetup -a' output to determine currently mapped
+    loopback devices. Output is expected to look like:
+
+        /dev/loop0: [0807]:961814 (/tmp/my.img)
+
+    :returns: dict: a dict mapping {loopback_dev: backing_file}
+    '''
+    loopbacks = {}
+    cmd = ['losetup', '-a']
+    devs = [d.strip().split(' ') for d in
+            check_output(cmd).splitlines() if d != '']
+    for dev, _, f in devs:
+        loopbacks[dev.replace(':', '')] = re.search('\((\S+)\)', f).groups()[0]
+    return loopbacks
+
+
+def create_loopback(file_path):
+    '''
+    Create a loopback device for a given backing file.
+
+    :returns: str: Full path to new loopback device (eg, /dev/loop0)
+    '''
+    file_path = os.path.abspath(file_path)
+    check_call(['losetup', '--find', file_path])
+    for d, f in six.iteritems(loopback_devices()):
+        if f == file_path:
+            return d
+
+
+def ensure_loopback_device(path, size):
+    '''
+    Ensure a loopback device exists for a given backing file path and size.
+    If it a loopback device is not mapped to file, a new one will be created.
+
+    TODO: Confirm size of found loopback device.
+
+    :returns: str: Full path to the ensured loopback device (eg, /dev/loop0)
+    '''
+    for d, f in six.iteritems(loopback_devices()):
+        if f == path:
+            return d
+
+    if not os.path.exists(path):
+        cmd = ['truncate', '--size', size, path]
+        check_call(cmd)
+
+    return create_loopback(path)
+
+
+def is_mapped_loopback_device(device):
+    """
+    Checks if a given device name is an existing/mapped loopback device.
+    :param device: str: Full path to the device (eg, /dev/loop1).
+    :returns: str: Path to the backing file if is a loopback device
+    empty string otherwise
+    """
+    return loopback_devices().get(device, "")