Reviewer comments

src/core/lib/iomgr/tcp_posix.cc

@@ -435,14 +435,13 @@ static void tcp_do_read(grpc_tcp* tcp) {
   GPR_TIMER_SCOPE("tcp_do_read", 0);
   struct msghdr msg;
   struct iovec iov[MAX_READ_IOVEC];
-  constexpr size_t cmsg_alloc_space =
-      CMSG_SPACE(sizeof(grpc_core::scm_timestamping)) + CMSG_SPACE(sizeof(int));
   ssize_t read_bytes;
   size_t total_read_bytes = 0;
   size_t iov_len =
       std::min<size_t>(MAX_READ_IOVEC, tcp->incoming_buffer->count);
+  constexpr size_t cmsg_alloc_space =
+      CMSG_SPACE(sizeof(grpc_core::scm_timestamping)) + CMSG_SPACE(sizeof(int));
   char cmsgbuf[cmsg_alloc_space];
-
   for (size_t i = 0; i < iov_len; i++) {
     iov[i].iov_base = GRPC_SLICE_START_PTR(tcp->incoming_buffer->slices[i]);
     iov[i].iov_len = GRPC_SLICE_LENGTH(tcp->incoming_buffer->slices[i]);