
the functionality of nullfs. The latter is now just a mount & unmount routine, and a few tables. umapfs borrow most of this infrastructure. Both fs's are now nfs-exportable. All layered fs's share a common format to private mount & private vnode structs (which a particular fs can extend). Also add genfs_noerr_rele(), a vnode op which will vrele/vput operand vnodes appropriately.