vfs_setmntpoint
vfs_setmntpoint(vfsp, uap->dir, 0);
vfs_setmntpoint(vfsp, mountpt, 0);
vfs_setmntpoint(vfsp, refstr_value(oldmntpt),
vfs_setmntpoint(&devices, "/devices", 0);
vfs_setmntpoint(&dev, "/dev", 0);
vfs_setmntpoint(rootvfs, "/", 0);
vfs_setmntpoint(vfsp, newpath, 0);
void vfs_setmntpoint(struct vfs *, const char *, uint32_t);