msdosfs_clusteralloc
int msdosfs_clusteralloc(struct msdosfsmount *, u_long, u_long, u_long *,
error = msdosfs_clusteralloc(pmp, cn, count, &cn, &got);
error = msdosfs_clusteralloc(pmp, 0, 1, &newcluster, NULL);
error = msdosfs_clusteralloc(pmp, 0, 1, &newcluster, NULL);