vfs_getvfsswbyvfsops
vswp = vfs_getvfsswbyvfsops(vfs_getops(vfsp));
if ((vswp = vfs_getvfsswbyvfsops(vfs_getops(rootvfs))) == NULL)
if ((vswp = vfs_getvfsswbyvfsops(vfs_getops(rootvfs))) != NULL) {
vswp = vfs_getvfsswbyvfsops(vfs_getops(rvp->v_vfsp));
struct vfssw *vfs_getvfsswbyvfsops(vfsops_t *);