static int io_recvmsg(struct io_kiocb *req, bool force_nonblock,
		      struct io_comp_state *cs)
{
	struct io_async_msghdr iomsg, *kmsg;
	struct socket *sock;
	struct io_buffer *kbuf;
	unsigned flags;
	int ret, cflags = 0;

	sock = sock_from_file(req->file, &ret);
	if (unlikely(!sock))
		return ret;

	if (req->io) {
		kmsg = &req->io->msg;
		kmsg->msg.msg_name = &req->io->msg.addr;
		/* if iov is set, it's allocated already */
		if (!kmsg->iov)
			kmsg->iov = kmsg->fast_iov;
		kmsg->msg.msg_iter.iov = kmsg->iov;
	} else {
		ret = io_recvmsg_copy_hdr(req, &iomsg);
		if (ret)
			return ret;
		kmsg = &iomsg;
	}

	if (req->flags & REQ_F_BUFFER_SELECT) {
		kbuf = io_recv_buffer_select(req, !force_nonblock);
		if (IS_ERR(kbuf))
			return PTR_ERR(kbuf);
		kmsg->fast_iov[0].iov_base = u64_to_user_ptr(kbuf->addr);
		iov_iter_init(&kmsg->msg.msg_iter, READ, kmsg->iov,
				1, req->sr_msg.len);
	}

	flags = req->sr_msg.msg_flags;
	if (flags & MSG_DONTWAIT)
		req->flags |= REQ_F_NOWAIT;
	else if (force_nonblock)
		flags |= MSG_DONTWAIT;

	ret = __sys_recvmsg_sock(sock, &kmsg->msg, req->sr_msg.umsg,
					kmsg->uaddr, flags);
	if (force_nonblock && ret == -EAGAIN)
		return io_setup_async_msg(req, kmsg);
	if (ret == -ERESTARTSYS)
		ret = -EINTR;

	if (req->flags & REQ_F_BUFFER_SELECTED)
		cflags = io_put_recv_kbuf(req);
	if (kmsg->iov != kmsg->fast_iov)
		kfree(kmsg->iov);
	req->flags &= ~REQ_F_NEED_CLEANUP;
	if (ret < 0)
		req_set_fail_links(req);
	__io_req_complete(req, ret, cflags, cs);
	return 0;
}
static int io_recvmsg(struct io_kiocb *req, bool force_nonblock,
		      struct io_comp_state *cs)
{
	struct io_async_msghdr iomsg, *kmsg;
	struct socket *sock;
	struct io_buffer *kbuf;
	unsigned flags;
	int ret, cflags = 0;

	sock = sock_from_file(req->file, &ret);
	if (unlikely(!sock))
		return ret;

	if (req->io) {
		kmsg = &req->io->msg;
		kmsg->msg.msg_name = &req->io->msg.addr;
		 
		if (!kmsg->iov)
			kmsg->iov = kmsg->fast_iov;
		kmsg->msg.msg_iter.iov = kmsg->iov;
	} else {
		ret = io_recvmsg_copy_hdr(req, &iomsg);
		if (ret)
			return ret;
		kmsg = &iomsg;
	}

	if (req->flags & REQ_F_BUFFER_SELECT) {
		kbuf = io_recv_buffer_select(req, !force_nonblock);
		if (IS_ERR(kbuf))
			return PTR_ERR(kbuf);
		kmsg->fast_iov[0].iov_base = u64_to_user_ptr(kbuf->addr);
		iov_iter_init(&kmsg->msg.msg_iter, READ, kmsg->iov,
				1, req->sr_msg.len);
	}

	flags = req->sr_msg.msg_flags;
	if (flags & MSG_DONTWAIT)
		req->flags |= REQ_F_NOWAIT;
	else if (force_nonblock)
		flags |= MSG_DONTWAIT;

	ret = __sys_recvmsg_sock(sock, &kmsg->msg, req->sr_msg.umsg,
					kmsg->uaddr, flags);
	if (force_nonblock && ret == -EAGAIN)
		return io_setup_async_msg(req, kmsg);
	if (ret == -ERESTARTSYS)
		ret = -EINTR;

	if (req->flags & REQ_F_BUFFER_SELECTED)
		cflags = io_put_recv_kbuf(req);
	if (kmsg->iov != kmsg->fast_iov)
		kfree(kmsg->iov);
	req->flags &= ~REQ_F_NEED_CLEANUP;
	if (ret < 0)
		req_set_fail_links(req);
	__io_req_complete(req, ret, cflags, cs);
	return 0;
}