A method for controlling access to a shared filesystem stored in a distributed data storage system is provided. The method can include storing a file comprising a shared filesystem as an inode object and a series of data block objects comprising the shared filesystem. Responding to a request from a client to open the file can include generating, in the shared filesystem, a client object, an open file object, and a client index object. The client object can be linked to the open file object and the client index object. The open file object and the client index object can be further linked to the inode object to indicate the file being accessed by the client. Related systems and articles of manufacture, including computer program products, are also provided.