Re: nfs subvolume access?

Ulli Horlacher
2021-03-11T07:47:46Z

On Wed 2021-03-10 (08:46), Ulli Horlacher wrote:
> When I try to access a btrfs filesystem via nfs, I get the error:
>
> root@tsmsrvi:~# mount tsmsrvj:/data/fex /nfs/tsmsrvj/fex
> root@tsmsrvi:~# time find /nfs/tsmsrvj/fex | wc -l
> find: File system loop detected; '/nfs/tsmsrvj/fex/spool' is part of the same file system loop as '/nfs/tsmsrvj/fex'.

It is even worse:

root@tsmsrvj:# grep localhost /etc/exports
/data/fex localhost(rw,async,no_subtree_check,no_root_squash)

root@tsmsrvj:# mount localhost:/data/fex /nfs/localhost/fex

root@tsmsrvj:# du -s /data/fex
64282240 /data/fex

root@tsmsrvj:# du -s /nfs/localhost/fex
du: WARNING: Circular directory structure.
This almost certainly means that you have a corrupted file system.
NOTIFY YOUR SYSTEM MANAGER.
The following directory is part of the cycle:
/nfs/localhost/fex/spool

0 /nfs/localhost/fex

root@tsmsrvj:# btrfs subvolume list /data
ID 257 gen 42 top level 5 path fex
ID 270 gen 42 top level 257 path fex/spool
ID 271 gen 21 top level 270 path fex/spool/.snapshot/2021-03-07_1453.test
ID 272 gen 23 top level 270 path fex/spool/.snapshot/2021-03-07_1531.test
ID 273 gen 25 top level 270 path fex/spool/.snapshot/2021-03-07_1532.test
ID 274 gen 27 top level 270 path fex/spool/.snapshot/2021-03-07_1718.test

root@tsmsrvj:# uname -a
Linux tsmsrvj 5.4.0-66-generic #74-Ubuntu SMP Wed Jan 27 22:54:38 UTC 2021 x86_64 x86_64 x86_64 GNU/Linux

root@tsmsrvj:# btrfs version
btrfs-progs v5.4.1

root@tsmsrvj:# dpkg -l | grep nfs-
ii nfs-common 1:1.3.4-2.5ubuntu3.3 amd64 NFS support files common to client and server
ii nfs-kernel-server 1:1.3.4-2.5ubuntu3.3 amd64 support for NFS kernel server

The same bug appears if nfs server and client are different hosts or the
client is an older Ubuntu 18.04 system.

--
Ullrich Horlacher Server und Virtualisierung
Rechenzentrum TIK
Universitaet Stuttgart E-Mail: horlacher@tik.uni-stuttgart.de
Allmandring 30a Tel: ++49-711-68565868
70569 Stuttgart (Germany) WWW: http://www.tik.uni-stuttgart.de/
REF:<20210310074620.GA2158@tik.uni-stuttgart.de>