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-rw-r--r--cloudinit/util.py83
1 files changed, 83 insertions, 0 deletions
diff --git a/cloudinit/util.py b/cloudinit/util.py
index ffe844b2..1e9ca5d9 100644
--- a/cloudinit/util.py
+++ b/cloudinit/util.py
@@ -1586,3 +1586,86 @@ def expand_package_list(version_fmt, pkgs):
raise RuntimeError("Invalid package type.")
return pkglist
+
+
+def get_mount_info(path, 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.
+ 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():
+ parts = line.split()
+
+ mount_point = parts[4]
+ mount_point_elements = [e for e in mount_point.split('/') if e]
+
+ # Ignore mounts deeper than the path in question.
+ if len(mount_point_elements) > len(path_elements):
+ continue
+
+ # Ignore mounts where the common path is not the same.
+ l = min(len(mount_point_elements), len(path_elements))
+ if mount_point_elements[0:l] != path_elements[0:l]:
+ continue
+
+ # Ignore mount points higher than an already seen mount
+ # point.
+ if (match_mount_point_elements is not None and
+ len(match_mount_point_elements) > len(mount_point_elements)):
+ continue
+
+ # Find the '-' which terminates a list of optional columns to
+ # find the filesystem type and the path to the device. See
+ # man 5 proc for the format of this file.
+ try:
+ i = parts.index('-')
+ except ValueError:
+ log.debug("Did not find column named '-' in %s",
+ mountinfo_path)
+ return None
+
+ # Get the path to the device.
+ try:
+ fs_type = parts[i + 1]
+ devpth = parts[i + 2]
+ except IndexError:
+ log.debug("Too few columns in %s after '-' column", mountinfo_path)
+ return None
+
+ match_mount_point = mount_point
+ match_mount_point_elements = mount_point_elements
+
+ if devpth and fs_type and match_mount_point:
+ return (devpth, fs_type, match_mount_point)
+ else:
+ return None