mount with fsc : an incorrect mount option was specified

(it's my firt use of serverfault and english is not my first langage, so be cool with me).

I want to use FSC cache on a NFS Share. It's a zpool on a OVH Server. I have 3 servers using this NFS share on Debian 11 (got the same issue in Debian 10, i upgrade it to test). but mount is not working :

mount.nfs: mount(2): Invalid argument
mount.nfs: an incorrect mount option was specified

it's a 4.19.0-14-amd64 kernel :

Linux nsXXX 4.19.0-14-amd64 #1 SMP Debian 4.19.171-2 (2021-01-30) x86_64 GNU/Linux

~~

The cachefilesd configuration :

daemon :

root@www:~# !sys
systemctl status cachefilesd.service
● cachefilesd.service - LSB: CacheFiles daemon
   Loaded: loaded (/etc/init.d/cachefilesd; generated)
   Active: active (running) since Sun 2021-10-10 20:45:06 CEST; 1 day 18h ago
     Docs: man:systemd-sysv-generator(8)
    Tasks: 1 (limit: 4915)
   Memory: 2.6M
   CGroup: /system.slice/cachefilesd.service
           └─2020 /sbin/cachefilesd

Oct 10 20:45:06 www.xxx.com systemd[1]: Starting LSB: CacheFiles daemon...
Oct 10 20:45:06 www.xxx.com cachefilesd[2016]: About to bind cache
Oct 10 20:45:06 www.xxx.com cachefilesd[2016]: Bound cache
Oct 10 20:45:06 www.xxx.com cachefilesd[2020]: Daemon Started
Oct 10 20:45:06 www.xxx.com cachefilesd[1988]: Starting FilesCache daemon : cachefilesd.
Oct 10 20:45:06 www.xxx.com systemd[1]: Started LSB: CacheFiles daemon.

cachefilesd configuration file :

# Defaults for cachefilesd initscript
# sourced by /etc/init.d/cachefilesd

# You must uncomment the run=yes line below for cachefilesd to start.
# Before doing so, please read /usr/share/doc/cachefilesd/howto.txt.gz as
# extended user attributes need to be enabled on the cache filesystem.
RUN=yes

# Additional options that are passed to the Daemon.
DAEMON_OPTS=""`

The last line is still commented because, uncomment is not working on Debian AppArmor .
The deamon is not starting.

**cachefiles.conf :**

`root@www:~# cat /etc/cachefilesd.conf
###############################################################################
#
# Copyright (C) 2006,2010 Red Hat, Inc. All Rights Reserved.
# Written by David Howells ([email protected])
#
# This program is free software; you can redistribute it and/or
# modify it under the terms of the GNU General Public License
# as published by the Free Software Foundation; either version
# 2 of the License, or (at your option) any later version.
#
###############################################################################

dir /var/cache/fscache
tag mycache
brun 10%
bcull 7%
bstop 3%
frun 10%
fcull 7%
fstop 3%

# Assuming you're using SELinux with the default security policy included in
# this package
#secctx system_u:system_r:cachefiles_kernel_t:s0

Volumes is not using FSC :

root@www:~# cat /proc/fs/nfsfs/volumes
NV SERVER   PORT DEV          FSID                              FSC
v3 0a184758  801 0:46         10800010019:0                     no
v4 36262d92  801 0:48         75f88f2900b390a8:0                no`

The mount configuration :
`root@www:~# nfsstat  -m
/data from 10.XXXX:/zpool-XXXXX/data
 Flags: rw,noatime,vers=3,rsize=1048576,wsize=1048576,namlen=255,hard,proto=tcp,timeo=600,retrans=2,sec=sys,mountaddr=10.XXXX,mountvers=3,mountport=48614,mountproto=udp,local_lock=none,addr=10.XXXX

I try a lot of thing :

• reducing rize from fsc option is ignored when trying to use cachefilesd on ubuntu 18.04
• trying to change the proto to udp
• change nfs.mount (sorry i lose the link)

Any idea to get it working or how to get information/log to figure out what is happening ?

Thanks you !