I have finished the module for Samba 2.2, it is now working with 2.2.9. There are not a lot of changes in Samba after 2.2.4, so it should work with versions 2.2.4 and up without problems. In versions before 2.2.4 there are changes in the VFS API which makes the module incompatible.
I have been using Mutex/MutexHandlers classes, which underneath use pthread_mutex_lock and pthread_mutex_unlock. This is needed to protect a linked list from access and modification from multiple threads. For data structures, I have been considering using STL's built-in support, but they seem overly complicated and somewhat painful.