M_NBDATA
mbp = malloc(sizeof(struct mbchain), M_NBDATA, M_WAITOK);
mdp = malloc(sizeof(struct mbchain), M_NBDATA, M_WAITOK);
free(mbp, M_NBDATA);
free(mdp, M_NBDATA);
free(mbp, M_NBDATA);
free(mdp, M_NBDATA);
free(mdp, M_NBDATA);
free(mdp, M_NBDATA);
free(mdp, M_NBDATA);
free(mdp, M_NBDATA);
nbp = malloc(sizeof *nbp, M_NBDATA, M_WAITOK);
free(nbp, M_NBDATA);