[Samba] Need some explanation on Samba/NFS locks handle

[Alain.Gorlier at altissemiconductor.com]

>> What kind of lock would the NFS client issue? 
Linux locks : /* F_RDLCK, F_WRLCK, F_UNLCK */

>> I don't know enough about NFS locking to really tell whether this is
>> possible at all and which semantics those locks would really have.

Imagine an NFS application that has to lock a file to inform others that 
the file is already used and should not be written (F_WRLCK).
In samba server, there is no check/no error reported to the SMB clients 
that the file is locked.
So a samba client can always access/write the file that is already used 
and locked by an NFS client.

>> Does this work across different NFS clients? And if yes, which syscall 
are used there?
The application has to be written to handle locks correctly. fcntl 
function ?

Do I miss something ?