nvlist_size
if (nvlist_size(jailparams, &nargv, NV_ENCODE_NATIVE) != 0)
nv->len = nvlist_size(nvl);
size_t nvlist_size(const nvlist_t *nvl);
assert(sz >= nvlist_size(nvl));
configblksz = nvlist_size(poolconfig);
*(uint64_t *)DN_BONUS(dnode) = nvlist_size(poolconfig);