Re: [PATCH v3 1/2] QIOChannelSocket: Introduce assert and reduce ifdefs to improve readability

[Daniel P . Berrangé]

On Tue, Jun 14, 2022 at 02:17:25AM -0300, Leonardo Bras wrote:
> During implementation of MSG_ZEROCOPY feature, a lot of #ifdefs were
> introduced, particularly at qio_channel_socket_writev().
> 
> Rewrite some of those changes so it's easier to read.
> 
> Also, introduce an assert to help detect incorrect zero-copy usage is when
> it's disabled on build.
> 
> Signed-off-by: Leonardo Bras <leobras@redhat.com>
> ---
>  io/channel-socket.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/io/channel-socket.c b/io/channel-socket.c
> index dc9c165de1..cdce7b0b45 100644
> --- a/io/channel-socket.c
> +++ b/io/channel-socket.c
> @@ -578,11 +578,13 @@ static ssize_t qio_channel_socket_writev(QIOChannel 
> *ioc,
>          memcpy(CMSG_DATA(cmsg), fds, fdsize);
>      }
>  
> -#ifdef QEMU_MSG_ZEROCOPY
>      if (flags & QIO_CHANNEL_WRITE_FLAG_ZERO_COPY) {
> +#ifdef QEMU_MSG_ZEROCOPY
>          sflags = MSG_ZEROCOPY;
> -    }
> +#else

I would just add a comment:

         /* We expect QIOChannel class entry point to have
            blocked this code path already */

> +        g_assert_unreachable();
>  #endif
> +    }
>  
>   retry:
>      ret = sendmsg(sioc->fd, &msg, sflags);
> @@ -592,15 +594,13 @@ static ssize_t qio_channel_socket_writev(QIOChannel 
> *ioc,
>              return QIO_CHANNEL_ERR_BLOCK;
>          case EINTR:
>              goto retry;
> -#ifdef QEMU_MSG_ZEROCOPY
>          case ENOBUFS:
> -            if (sflags & MSG_ZEROCOPY) {
> +            if (flags & QIO_CHANNEL_WRITE_FLAG_ZERO_COPY) {
>                  error_setg_errno(errp, errno,
>                                   "Process can't lock enough memory for using 
> MSG_ZEROCOPY");
>                  return -1;
>              }
>              break;
> -#endif
>          }
>  
>          error_setg_errno(errp, errno,

Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>


With regards,
Daniel
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