Well, the name sounds big but what we mean is that the vfs.Filesystem interface would include most (if not all) most-used filesystem calls.

This would require adding support for Hard Links, and Interface methods for changing permissions and ownership IF the underlying Virtual File System chooses to implement it. Else, each implementation would detail whether that Filesystem call would return an ErrNotImplemented, continue as if nothing happened without doing anything, or actually taking the parameters into account for proper functioning of the VFS.