mount parse: Fix matching non-existent directories (#4222)

This puts `util.mount_parse()` now on-par with
`util.mount_parse_info()`.
Fix two now failing tests to clarify the new behaviour.

Fixes GH-4193

Sponsored by: The FreeBSD Foundation

cloudinit/util.py

@@ -2677,6 +2677,8 @@ def get_device_info_from_zpool(zpool):
 
 
 def parse_mount(path, get_mnt_opts=False):
+    """Return the mount information for PATH given the lines ``mount(1)``
+    This function is compatible with ``util.parse_mount_info()``"""
     (mountoutput, _err) = subp.subp(["mount"])
 
     # there are 2 types of mount outputs we have to parse therefore
@@ -2738,21 +2740,27 @@ def parse_mount(path, get_mnt_opts=False):
         # continue finding the real device like '/dev/da0'.
         # this is only valid for non zfs file systems as a zpool
         # can have gpt labels as disk.
+        # It also doesn't really make sense for NFS.
         devm = re.search("^(/dev/.+)[sp]([0-9])$", devpth)
         if not devm and is_FreeBSD() and fs_type not in ["zfs", "nfs"]:
-            devpth = get_freebsd_devpth(path)
+            # don't duplicate the effort of finding the mountpoint in
+            # ``get_freebsd_devpth()`` by passing it the ``path``
+            # instead only resolve the ``devpth``
+            devpth = get_freebsd_devpth(devpth)
+        match_devpth = devpth
 
         if match_mount_point == path:
             break
 
-    if mount_point and path in mount_point:
-        if get_mnt_opts:
-            if devpth and fs_type and match_mount_point and mount_options:
-                return (devpth, fs_type, match_mount_point, mount_options)
-        else:
-            if devpth and fs_type and match_mount_point:
-                return (devpth, fs_type, match_mount_point)
-    return None
+    if not match_mount_point or match_mount_point not in path:
+        # return early here, so we can actually read what's happening below
+        return None
+    if get_mnt_opts:
+        if match_devpth and fs_type and match_mount_point and mount_options:
+            return (match_devpth, fs_type, match_mount_point, mount_options)
+    else:
+        if match_devpth and fs_type and match_mount_point:
+            return (match_devpth, fs_type, match_mount_point)
 
 
 def get_mount_info(path, log=LOG, get_mnt_opts=False):

tests/unittests/test_util.py

@@ -2201,9 +2201,9 @@ def test_parse_mount_with_ext(self, mount_out):
         # this one exists in mount_parse_ext.txt
         ret = util.parse_mount("/sys/kernel/debug")
         self.assertEqual(("none", "debugfs", "/sys/kernel/debug"), ret)
-        # this one does not even exist in mount_parse_ext.txt
-        ret = util.parse_mount("/not/existing/mount")
-        self.assertIsNone(ret)
+        # this one does not exist in mount_parse_ext.txt
+        ret = util.parse_mount("/var/tmp/cloud-init")
+        self.assertEqual(("/dev/mapper/vg00-lv_var", "ext4", "/var"), ret)
 
     @mock.patch("cloudinit.subp.subp")
     def test_parse_mount_with_zfs(self, mount_out):
@@ -2217,9 +2217,9 @@ def test_parse_mount_with_zfs(self, mount_out):
         # this one is the root, valid and also exists in mount_parse_zfs.txt
         ret = util.parse_mount("/")
         self.assertEqual(("vmzroot/ROOT/freebsd", "zfs", "/"), ret)
-        # this one does not even exist in mount_parse_ext.txt
-        ret = util.parse_mount("/not/existing/mount")
-        self.assertIsNone(ret)
+        # this one does not exist in mount_parse_ext.txt
+        ret = util.parse_mount("/var/tmp/cloud-init")
+        self.assertEqual(("vmzroot/var/tmp", "zfs", "/var/tmp"), ret)
 
 
 class TestIsX86(helpers.CiTestCase):