freezing

[d-a-v]

Hi,

Here is a simple script that freezes the caller when accessing to the mounted directory.
It freezes on debian jessie (unionfs-0.24-2.2, fuse-2.9.3-15 (not 2.3.9)) and ubuntu xenial (unionfs-1.0-1, fuse-2.9.4-1).
Last time I checked, this used to work back in 2014 on debian wheezy. I'll try again on this version to check on fuse and unionfs versions.

#!/bin/sh
mkdir -p /test /testok

echo a > /test/a
echo b > /test/b

mkdir -p /tmp/rootbind
mount -o bind / /tmp/rootbind

mkdir -p /tmp/rw

#unionfs-fuse -o allow_other,use_ino,suid,dev,nonempty /tmp/rootbind/test=RO:/tmp/rw=RW /testok
unionfs-fuse -o allow_other,use_ino,suid,dev,nonempty /tmp/rootbind/test=RO:/tmp/rw=RW /test

[d-a-v]

It seems that the bugs comes from elsewhere. The script above works with :

• the current unionfs-fuse github source
• fuse version 2.8.1-1.1ubuntu3.1 (the one in ubuntu lucid 10.04)
• kernel 2.6.32 (ubuntu 10.04)
• the updated last line of the script (option cow, and =RW:=RO in this order):
  unionfs-fuse -o allow_other,use_ino,suid,dev,nonempty,cow /tmp/rw=RW:/tmp/rootbind/test=RO /test

I'll continue to dig ou the problem. Even if this seems not be a unionfs-fuse problem, I hope the issue can stay opened until the cause if found.

[d-a-v]

I ran more tests and I appears that bug comes with the kernel fuse driver api 7.23.
It becomes clear now that this is not specific to unionfs-fuse.
I presume I should go to fuse now.
Thanks to have read :)

[rpodgorny]

hi! no problem at all! feel free to open new tickets when unsure in the future...

[bsbernd]

Hi David, I will try to reproduce later on today or over the weekend. On a few glance this looks like a some kind of recursive access issue. If should get more information in the mean time, please let us know here (or on the mailing list).

Thanks,
Bernd

[d-a-v]

Yes this script mounts an existing directory above itself with modifcations pushed to another one.
This is working with linux kernel <=3, not with v4+.
I'm aware I'm (was) exploiting some sort of out-of-purpose side effect.