1. A computer-implemented method for controlling data access by users of a file system, comprising the steps of: receiving a request for a change in user access rights of one of said users to a designated storage element of said file system, wherein said file system comprises storage elements, respective first portions of said storage elements being owned by data owners that control said user access rights thereto, and a user repository in said file system includes groups of said users, wherein said groups have common access rights to respective second portions of said storage elements; identifying one of said groups, wherein said common access rights of said identified group include said designated storage element; obtaining a consent to said request from said data owner of said designated storage element; and responsively to said consent adjusting a membership of said one user in said identified group to conform said user access rights of said one user to said designated storage element to said request.