Each vnode or VFS has a set of operations that can be applied to it. The most obvious are %vn_op and %vfs_op. Here, op refers to the respective Vnode and VFS operations as described in Appendices sec-appendix-vnode-vnodeops and sec-appendix-vnode-vfsops. For example, %vn_getattr refers to the vnode operation ``get attributes,'' and %vfs_statvfs refers to the VFS operation ``get file system statistics.''
It is often useful to refer to a group of vnode operations as a whole. Generally, a user who wants to perform an operation on one type of data will want that operation to be applied everywhere the same type of data object is used. For example, in Envfs (Appendix sec-appendix-typical-in-core-envfs) environment variables in pathnames should be expanded everywhere pathnames are used, not just, say, in the vn_open function. FiST provides meta-function operators that start with %vn_op and %vfs_op. These meta-functions are listed in Table tab-fist-func-meta.