[Samba] About dfree command directive

[Luis Felipe Dominguez Vega]

Hello everyone, i need known if samba (4.5.2-Debian) disable the "dfree 
command" directive, because i create a script that simple write "hello" to a 
file and when i connect to my share, tell the free space, but the script never 
execute.
The main need is that i used btrfs subvolumes with quotas for some shares and 
in batch i wrote a script that "echoes" the free and size (in quota system), 
because df dont work here.
So if dfree command not working, What is that i need to do?