New submission from Matt Christopher <hydr...@gmail.com>:
I've got a case where we mount a CIFS filesystem and then later the actual
backing filesystem is deleted (but the mount remains on the machine).
When running from a shell, this is the behavior which I see after the backing
CIFS filesystem has gone away:
root@1b20608623a246f1af69058acdfbfd30000006:/fsmounts# ll
ls: cannot access 'cifsmountpoint': Input/output error
total 8
drwxrwx--- 3 _user _grp 4096 Aug 15 15:46 ./
drwxrwx--- 8 _user _grp 4096 Aug 15 15:46 ../
d????????? ? ? ? ? ? cifsmountpoint/
root@1b20608623a246f1af69058acdfbfd30000006:/fsmounts# stat -c "%d"
cifsmountpoint
stat: cannot stat 'cifsmountpoint': Input/output error
Running mount -l shows this:
//<redacted>/c7e868cd-3047-4881-b05b-a1a1d087dbf5 on /fsmounts/cifsmountpoint
type cifs
(rw,relatime,vers=3.0,cache=strict,username=<redacted>,domain=,uid=0,noforceuid,gid=0,noforcegid,addr=52.239.160.104,file_mode=0777,dir_mode=0777,soft,persistenthandles,nounix,serverino,mapposix,rsize=1048576,wsize=1048576,echo_interval=60,actimeo=1)
In the Python code that I see posixpath.py has this snippet:
try:
s1 = os.lstat(path)
except (OSError, ValueError):
# It doesn't exist -- so not a mount point. :-)
return False
The problem is that the comment: "# It doesn't exist -- so not a mount point.
:-)" assumes a particular kind of OSError - in reality not every OS error means
that it doesn't exist. In this case we're getting OSError with errno == 5,
which is:
OSError: [Errno 5] Input/output error:
Now, I'm not entirely sure what (if anything) the ismount function is supposed
to be doing here... but returning false seems incorrect. This IS a mount, and
you can see so via mount -l.
I am aware that there are other libraries (i.e. psutil.disk_partitions) which
can help me to detect this situation but I was surprised that ismount was
saying false here. It seems like it should possibly just raise, or maybe
there's a fancy way to check mounts if lstat fails.
This looks kinda related to https://bugs.python.org/issue2466 (although this is
already fixed and not exactly the same problem it's a similar class of issue)
----------
messages: 349833
nosy: Matt Christopher
priority: normal
severity: normal
status: open
title: os.path.ismount returns false for disconnected CIFS mounts in Linux
type: behavior
versions: Python 3.6
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Python tracker <rep...@bugs.python.org>
<https://bugs.python.org/issue37870>
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