limit-fs is an elegant solution, for avoiding the uncontrolled growth of space occupied by backup and log files.
A filesystem manages how information is stored and recovered. Information is grouped in files, which are structured hierarchically, in order to facilitate their sorting.
There are many kinds of filesystems, and userspace (FUSE) ones are quite peculiar. Userspace filesystems allow non-privileged users to run the code of a filesystem in user space. The FUSE module acts as the only "bridge" to the kernel.