Re: [PATCH v7 2/5] QIOChannelSocket: Implement io_writev zero copy flag & io_flush for CONFIG_LINUX

[Peter Xu]

On Thu, Jan 06, 2022 at 07:13:39PM -0300, Leonardo Bras wrote:
> @@ -558,15 +575,26 @@ static ssize_t qio_channel_socket_writev(QIOChannel 
> *ioc,
>          memcpy(CMSG_DATA(cmsg), fds, fdsize);
>      }
>  
> +    if (flags & QIO_CHANNEL_WRITE_FLAG_ZERO_COPY) {
> +        sflags = MSG_ZEROCOPY;
> +    }
> +
>   retry:
> -    ret = sendmsg(sioc->fd, &msg, 0);
> +    ret = sendmsg(sioc->fd, &msg, sflags);
>      if (ret <= 0) {
> -        if (errno == EAGAIN) {
> +        switch (errno) {
> +        case EAGAIN:
>              return QIO_CHANNEL_ERR_BLOCK;
> -        }
> -        if (errno == EINTR) {
> +        case EINTR:
>              goto retry;
> +        case ENOBUFS:
> +            if (sflags & MSG_ZEROCOPY) {
> +                error_setg_errno(errp, errno,
> +                                 "Process can't lock enough memory for using 
> MSG_ZEROCOPY");
> +                return -1;
> +            }

I have no idea whether it'll make a real differnece, but - should we better add
a "break" here?  If you agree and with that fixed, feel free to add:

Reviewed-by: Peter Xu <peterx@redhat.com>

I also wonder whether you hit ENOBUFS in any of the environments.  On Fedora
here it's by default unlimited, but just curious when we should keep an eye.

Thanks,

-- 
Peter Xu