refactor get_mount_info and add tests

1) Refactor util.get_mount_info() to facilitate unit testing.
2) Add unit tests for /proc/$$/mountinfo parsing.

2 files changed, 149 insertions, 34 deletions

diff --git a/cloudinit/util.py b/cloudinit/util.py
index 709d5cca..a1f6e004 100644
--- a/cloudinit/util.py
+++ b/cloudinit/util.py
@@ -1576,44 +1576,29 @@ def expand_package_list(version_fmt, pkgs):
     return pkglist
 
 
-def get_mount_info(path, log=LOG):
-    # Use /proc/$$/mountinfo to find the device where path is mounted.
-    # This is done because with a btrfs filesystem using os.stat(path)
-    # does not return the ID of the device.
-    #
-    # Here, / has a device of 18 (decimal).
-    #
-    # $ stat /
-    #   File: '/'
-    #   Size: 234               Blocks: 0          IO Block: 4096   directory
-    # Device: 12h/18d   Inode: 256         Links: 1
-    # Access: (0755/drwxr-xr-x)  Uid: (    0/    root)   Gid: (    0/    root)
-    # Access: 2013-01-13 07:31:04.358011255 +0000
-    # Modify: 2013-01-13 18:48:25.930011255 +0000
-    # Change: 2013-01-13 18:48:25.930011255 +0000
-    #  Birth: -
-    #
-    # Find where / is mounted:
-    #
-    # $ mount | grep ' / '
-    # /dev/vda1 on / type btrfs (rw,subvol=@,compress=lzo)
-    #
-    # And the device ID for /dev/vda1 is not 18:
-    #
-    # $ ls -l /dev/vda1
-    # brw-rw---- 1 root disk 253, 1 Jan 13 08:29 /dev/vda1
-    #
-    # So use /proc/$$/mountinfo to find the device underlying the
-    # input path.
+def parse_mount_info(path, mountinfo_lines, log=LOG):
+    """Return the mount information for PATH given the lines from
+    /proc/$$/mountinfo."""
+
     path_elements = [e for e in path.split('/') if e]
     devpth = None
     fs_type = None
     match_mount_point = None
     match_mount_point_elements = None
-    mountinfo_path = '/proc/%s/mountinfo' % os.getpid()
-    for line in load_file(mountinfo_path).splitlines():
+    for i, line in enumerate(mountinfo_lines):
         parts = line.split()
 
+        # Completely fail if there is anything in any line that is
+        # unexpected, as continuing to parse past a bad line could
+        # cause an incorrect result to be returned, so it's better
+        # return nothing than an incorrect result.
+
+        # The minimum number of elements in a valid line is 10.
+        if len(parts) < 10:
+            log.debug("Line %d has two few columns (%d): %s",
+                      i + 1, len(parts), line)
+            return None
+
         mount_point = parts[4]
         mount_point_elements = [e for e in mount_point.split('/') if e]
 
@@ -1638,8 +1623,8 @@ def get_mount_info(path, log=LOG):
         try:
             i = parts.index('-')
         except ValueError:
-            log.debug("Did not find column named '-' in %s",
-                      mountinfo_path)
+            log.debug("Did not find column named '-' in line %d: %s",
+                      i + 1, line)
             return None
 
         # Get the path to the device.
@@ -1647,7 +1632,8 @@ def get_mount_info(path, log=LOG):
             fs_type = parts[i + 1]
             devpth = parts[i + 2]
         except IndexError:
-            log.debug("Too few columns in %s after '-' column", mountinfo_path)
+            log.debug("Too few columns after '-' column in line %d: %s",
+                      i + 1, line)
             return None
 
         match_mount_point = mount_point
@@ -1657,3 +1643,37 @@ def get_mount_info(path, log=LOG):
         return (devpth, fs_type, match_mount_point)
     else:
         return None
+
+
+def get_mount_info(path, log=LOG):
+    # Use /proc/$$/mountinfo to find the device where path is mounted.
+    # This is done because with a btrfs filesystem using os.stat(path)
+    # does not return the ID of the device.
+    #
+    # Here, / has a device of 18 (decimal).
+    #
+    # $ stat /
+    #   File: '/'
+    #   Size: 234               Blocks: 0          IO Block: 4096   directory
+    # Device: 12h/18d   Inode: 256         Links: 1
+    # Access: (0755/drwxr-xr-x)  Uid: (    0/    root)   Gid: (    0/    root)
+    # Access: 2013-01-13 07:31:04.358011255 +0000
+    # Modify: 2013-01-13 18:48:25.930011255 +0000
+    # Change: 2013-01-13 18:48:25.930011255 +0000
+    #  Birth: -
+    #
+    # Find where / is mounted:
+    #
+    # $ mount | grep ' / '
+    # /dev/vda1 on / type btrfs (rw,subvol=@,compress=lzo)
+    #
+    # And the device ID for /dev/vda1 is not 18:
+    #
+    # $ ls -l /dev/vda1
+    # brw-rw---- 1 root disk 253, 1 Jan 13 08:29 /dev/vda1
+    #
+    # So use /proc/$$/mountinfo to find the device underlying the
+    # input path.
+    mountinfo_path = '/proc/%s/mountinfo' % os.getpid()
+    lines = load_file(mountinfo_path).splitlines()
+    return parse_mount_info(path, lines, log)
diff --git a/tests/unittests/test_util.py b/tests/unittests/test_util.py
index 02611581..7ff9a57f 100644
--- a/tests/unittests/test_util.py
+++ b/tests/unittests/test_util.py
@@ -248,4 +248,99 @@ class TestLoadYaml(TestCase):
                          myobj)
 
 
+class TestMountinfoParsing(TestCase):
+    precise_ext4_mountinfo = \
+"""15 20 0:14 / /sys rw,nosuid,nodev,noexec,relatime - sysfs sysfs rw
+16 20 0:3 / /proc rw,nosuid,nodev,noexec,relatime - proc proc rw
+17 20 0:5 / /dev rw,relatime - devtmpfs udev rw,size=16422216k,nr_inodes=4105554,mode=755
+18 17 0:11 / /dev/pts rw,nosuid,noexec,relatime - devpts devpts rw,gid=5,mode=620,ptmxmode=000
+19 20 0:15 / /run rw,nosuid,relatime - tmpfs tmpfs rw,size=6572812k,mode=755
+20 1 252:1 / / rw,relatime - ext4 /dev/mapper/vg0-root rw,errors=remount-ro,data=ordered
+21 15 0:16 / /sys/fs/cgroup rw,relatime - tmpfs cgroup rw,mode=755
+22 15 0:17 / /sys/fs/fuse/connections rw,relatime - fusectl none rw
+23 15 0:6 / /sys/kernel/debug rw,relatime - debugfs none rw
+25 15 0:10 / /sys/kernel/security rw,relatime - securityfs none rw
+26 19 0:19 / /run/lock rw,nosuid,nodev,noexec,relatime - tmpfs none rw,size=5120k
+27 19 0:20 / /run/shm rw,nosuid,nodev,relatime - tmpfs none rw
+28 19 0:21 / /run/user rw,nosuid,nodev,noexec,relatime - tmpfs none rw,size=102400k,mode=755
+24 21 0:18 / /sys/fs/cgroup/cpuset rw,relatime - cgroup cgroup rw,cpuset
+29 21 0:22 / /sys/fs/cgroup/cpu rw,relatime - cgroup cgroup rw,cpu
+30 21 0:23 / /sys/fs/cgroup/cpuacct rw,relatime - cgroup cgroup rw,cpuacct
+31 21 0:24 / /sys/fs/cgroup/memory rw,relatime - cgroup cgroup rw,memory
+32 21 0:25 / /sys/fs/cgroup/devices rw,relatime - cgroup cgroup rw,devices
+33 21 0:26 / /sys/fs/cgroup/freezer rw,relatime - cgroup cgroup rw,freezer
+34 21 0:27 / /sys/fs/cgroup/blkio rw,relatime - cgroup cgroup rw,blkio
+35 21 0:28 / /sys/fs/cgroup/perf_event rw,relatime - cgroup cgroup rw,perf_event
+36 20 9:0 / /boot rw,relatime - ext4 /dev/md0 rw,data=ordered
+37 16 0:29 / /proc/sys/fs/binfmt_misc rw,nosuid,nodev,noexec,relatime - binfmt_misc binfmt_misc rw
+39 28 0:30 / /run/user/foobar/gvfs rw,nosuid,nodev,relatime - fuse.gvfsd-fuse gvfsd-fuse rw,user_id=1000,group_id=1000"""
+
+    raring_btrfs_mountinfo = \
+"""15 20 0:14 / /sys rw,nosuid,nodev,noexec,relatime - sysfs sysfs rw
+16 20 0:3 / /proc rw,nosuid,nodev,noexec,relatime - proc proc rw
+17 20 0:5 / /dev rw,relatime - devtmpfs udev rw,size=865556k,nr_inodes=216389,mode=755
+18 17 0:11 / /dev/pts rw,nosuid,noexec,relatime - devpts devpts rw,gid=5,mode=620,ptmxmode=000
+19 20 0:15 / /run rw,nosuid,relatime - tmpfs tmpfs rw,size=348196k,mode=755
+20 1 0:16 /@ / rw,relatime - btrfs /dev/vda1 rw,compress=lzo,space_cache
+21 15 0:19 / /sys/fs/fuse/connections rw,relatime - fusectl none rw
+22 15 0:6 / /sys/kernel/debug rw,relatime - debugfs none rw
+23 15 0:10 / /sys/kernel/security rw,relatime - securityfs none rw
+24 19 0:20 / /run/lock rw,nosuid,nodev,noexec,relatime - tmpfs none rw,size=5120k
+25 19 0:21 / /run/shm rw,nosuid,nodev,relatime - tmpfs none rw
+26 19 0:22 / /run/user rw,nosuid,nodev,noexec,relatime - tmpfs none rw,size=102400k,mode=755
+27 20 0:16 /@home /home rw,relatime - btrfs /dev/vda1 rw,compress=lzo,space_cache"""
+
+    def test_invalid_mountinfo(self):
+        line = "20 1 252:1 / / rw,relatime - ext4 /dev/mapper/vg0-root rw,errors=remount-ro,data=ordered"
+        elements = line.split()
+        for i in range(len(elements) + 1):
+            lines = [' '.join(elements[0:i])]
+            if i < 10:
+                expected = None
+            else:
+                expected = ('/dev/mapper/vg0-root', 'ext4', '/')
+            self.assertEqual(expected, util.parse_mount_info('/', lines))
+
+    def test_precise_ext4_root(self):
+        lines = TestMountinfoParsing.precise_ext4_mountinfo.splitlines()
+
+        expected = ('/dev/mapper/vg0-root', 'ext4', '/')
+        self.assertEqual(expected, util.parse_mount_info('/', lines))
+        self.assertEqual(expected, util.parse_mount_info('/usr', lines))
+        self.assertEqual(expected, util.parse_mount_info('/usr/bin', lines))
+
+        expected = ('/dev/md0', 'ext4', '/boot')
+        self.assertEqual(expected, util.parse_mount_info('/boot', lines))
+        self.assertEqual(expected, util.parse_mount_info('/boot/grub', lines))
+
+        expected = ('/dev/mapper/vg0-root', 'ext4', '/')
+        self.assertEqual(expected, util.parse_mount_info('/home', lines))
+        self.assertEqual(expected, util.parse_mount_info('/home/me', lines))
+
+        expected = ('tmpfs', 'tmpfs', '/run')
+        self.assertEqual(expected, util.parse_mount_info('/run', lines))
+
+        expected = ('none', 'tmpfs', '/run/lock')
+        self.assertEqual(expected, util.parse_mount_info('/run/lock', lines))
+
+    def test_raring_btrfs_root(self):
+        lines = TestMountinfoParsing.raring_btrfs_mountinfo.splitlines()
+
+        expected = ('/dev/vda1', 'btrfs', '/')
+        self.assertEqual(expected, util.parse_mount_info('/', lines))
+        self.assertEqual(expected, util.parse_mount_info('/usr', lines))
+        self.assertEqual(expected, util.parse_mount_info('/usr/bin', lines))
+        self.assertEqual(expected, util.parse_mount_info('/boot', lines))
+        self.assertEqual(expected, util.parse_mount_info('/boot/grub', lines))
+
+        expected = ('/dev/vda1', 'btrfs', '/home')
+        self.assertEqual(expected, util.parse_mount_info('/home', lines))
+        self.assertEqual(expected, util.parse_mount_info('/home/me', lines))
+
+        expected = ('tmpfs', 'tmpfs', '/run')
+        self.assertEqual(expected, util.parse_mount_info('/run', lines))
+
+        expected = ('none', 'tmpfs', '/run/lock')
+        self.assertEqual(expected, util.parse_mount_info('/run/lock', lines))
+
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