services/fuse/arvados_fuse/unmount.py

   1 import collections
   2 import errno
   3 import os
   4 import subprocess
   5 import time
   6
   7
   8 MountInfo = collections.namedtuple(
   9     'MountInfo', ['is_fuse', 'major', 'minor', 'mnttype', 'path'])
  10
  11
  12 def mountinfo():
  13     mi = []
  14     with open('/proc/self/mountinfo') as f:
  15         for m in f.readlines():
  16             mntid, pmntid, dev, root, path, extra = m.split(" ", 5)
  17             mnttype = extra.split(" - ")[1].split(" ", 1)[0]
  18             major, minor = dev.split(":")
  19             mi.append(MountInfo(
  20                 is_fuse=(mnttype == "fuse" or mnttype.startswith("fuse.")),
  21                 major=major,
  22                 minor=minor,
  23                 mnttype=mnttype,
  24                 path=path,
  25             ))
  26     return mi
  27
  28
  29 def unmount(path, timeout=10, recursive=False):
  30     """Unmount the fuse mount at path.
  31
  32     Unmounting is done by writing 1 to the "abort" control file in
  33     sysfs to kill the fuse driver process, then executing "fusermount
  34     -u -z" to detach the mount point, and repeating these steps until
  35     the mount is no longer listed in /proc/self/mountinfo.
  36
  37     This procedure should enable a non-root user to reliably unmount
  38     their own fuse filesystem without risk of deadlock.
  39
  40     Returns True if unmounting was successful, False if it wasn't a
  41     fuse mount at all. Raises an exception if it cannot be unmounted.
  42     """
  43
  44     path = os.path.realpath(path)
  45
  46     if recursive:
  47         paths = []
  48         for m in mountinfo():
  49             if m.path == path or m.path.startswith(path+"/"):
  50                 paths.append(m.path)
  51                 if not m.is_fuse:
  52                     raise Exception(
  53                         "cannot unmount {}: non-fuse mountpoint {}".format(
  54                             path, m))
  55         for path in sorted(paths, key=len, reverse=True):
  56             unmount(path, timeout=timeout, recursive=False)
  57         return len(paths) > 0
  58
  59     was_mounted = False
  60     attempted = False
  61     if timeout is None:
  62         deadline = None
  63     else:
  64         deadline = time.time() + timeout
  65
  66     while True:
  67         mounted = False
  68         for m in mountinfo():
  69             if m.is_fuse:
  70                 try:
  71                     if os.path.realpath(m.path) == path:
  72                         was_mounted = True
  73                         mounted = True
  74                         break
  75                 except OSError:
  76                     continue
  77         if not mounted:
  78             return was_mounted
  79
  80         if attempted:
  81             delay = 1
  82             if deadline:
  83                 delay = min(delay, deadline - time.time())
  84                 if delay <= 0:
  85                     raise Exception("timed out")
  86             time.sleep(delay)
  87
  88         try:
  89             with open('/sys/fs/fuse/connections/{}/abort'.format(m.minor),
  90                       'w') as f:
  91                 f.write("1")
  92         except OSError as e:
  93             if e.errno != errno.ENOENT:
  94                 raise
  95
  96         attempted = True
  97         try:
  98             subprocess.check_call(["fusermount", "-u", "-z", path])
  99         except subprocess.CalledProcessError:
 100             pass