wapbl_write_commit
error = wapbl_write_commit(wl, head, tail);
error = wapbl_write_commit(wl, head, tail);
error = wapbl_write_commit(wl, head, tail);
static int wapbl_write_commit(struct wapbl *, off_t, off_t);
error = wapbl_write_commit(wl, wl->wl_head, wl->wl_tail);