POHMELFS got full read/write support
as well as directory listing and file creation.
All operations are not group-aware though, i.e. all writes are made only into single group and reads (directory listing and object lookup) do not balance between multiple groups.
There was a fair number of inode/dentry hacks and I suppose that populating dentry cache from outside of directory inode operations (like ->create() callback) is not a good idea, but I ended up adding new dentries when reading directory content in ->lookup() or ->readdir().
POHMELFS also does not yet handle errors – i.e. it is a luck we do not crash if server returns borrked structures for directory for example, network errors are not fixed also – client will not reconnect and will not even drop connection if some errors are found.
But it is a matter of time to clean things up. Stay tuned!