zfs_refcount_add_few
zfs_refcount_add_few(&zs->zs_blocks, pf_nblks + ipf_iend - ipf_istart,
zfs_refcount_add_few(&mc->mc_alloc_slots[allocator], slots,
void zfs_refcount_add_few(zfs_refcount_t *, uint64_t, const void *);