samba - Aug 2012 - shadow_copy2 is not working for me on samba 3.6.7 and btrfs volume

Hi,

I'm running samba 3.6.7 on a linux server:

root at SRVUBUNTU:/btrfs/samba/.btrfs# smbd -V
Version 3.6.7
root at SRVUBUNTU:/btrfs/samba/.btrfs# uname -a
Linux SRVUBUNTU 3.5.2 #1 SMP Fri Aug 17 15:26:57 CEST 2012 x86_64 x86_64
x86_64 GNU/Linux

I have a base dir to share with samba on /btrfs/samba

root at SRVUBUNTU:/btrfs/samba# ls -l
total 0
-rw-r--r-- 1 root root 0 Aug 24 13:07 a
-rw-r--r-- 1 root root 0 Aug 24 13:07 b

My snapshots are stored inside this basedir in the folder .btrfs

root at SRVUBUNTU:/btrfs/samba/.btrfs# ls -l
total 0
drwxr-xr-x 1 root root 12 Aug 24 13:15 @GMT-2012.08.24-15.15.25
drwxr-xr-x 1 root root 16 Aug 24 13:07 @GMT-2012.08.24-15.26.40

This is my smb.conf
-------------------
[data]
   vfs objects = shadow_copy2
   shadow:snapdir = /btrfs/samba/.btrfs
   shadow:basedir = /btrfs/samba
   read only = no
   path = /btrfs/samba/
   browsable = yes
   guest ok = yes
   follow symlinks = yes
   wide links      = yes
   unix extensions = no
------------------------------------

I can't see the snapshots in "previous versions", however I can
navigate/browse inside the windows 7 client to the (hidden) snapshot
directory, so it seems not to be a permission issue.
This worked previously fine for me on a freebsd server with zfs volumes.