in lustre 2.1 and up, the lustre_fill_super() was changed to expect the anonymous pointer to be of the type struct lustre_mount_data2. however, the ifdef for lustre_get_sb() for kernels < 2.6.18 was not updated. the attached patch seems to fix things but you might run into trouble when nfs exporting from these old kernels since lmd_mnt cannot be filled in for these older kernels.