run_remove_range
if (!run_remove_range(run_da, vcn, clen,
if (!run_remove_range(run_da, vcn, flen, &da_len)) {
if (!run_remove_range(run_da, new_alen, vcn - new_alen,
bool run_remove_range(struct runs_tree *run, CLST vcn, CLST len, CLST *done);