Re: [PATCH 26/33] io/channel-socket: introduce qio_channel_socket_keep_nonblock()

["Daniel P. Berrangé" <berrange@redhat.com>]

On Wed, Aug 13, 2025 at 07:48:47PM +0300, Vladimir Sementsov-Ogievskiy wrote:
> Add a possibility to keep socket non-block status when passing
> through qio channel. We need this to support migration of open
> fds through migration channel.
> 
> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
> ---
>  include/io/channel-socket.h |  3 +++
>  io/channel-socket.c         | 16 ++++++++++++----
>  2 files changed, 15 insertions(+), 4 deletions(-)
> 
> diff --git a/include/io/channel-socket.h b/include/io/channel-socket.h
> index a88cf8b3a9..0a4327d745 100644
> --- a/include/io/channel-socket.h
> +++ b/include/io/channel-socket.h
> @@ -49,6 +49,7 @@ struct QIOChannelSocket {
>      socklen_t remoteAddrLen;
>      ssize_t zero_copy_queued;
>      ssize_t zero_copy_sent;
> +    bool keep_nonblock;
>  };
>  
>  
> @@ -275,4 +276,6 @@ int qio_channel_socket_set_send_buffer(QIOChannelSocket *ioc,
>                                         size_t size,
>                                         Error **errp);
>  
> +void qio_channel_socket_keep_nonblock(QIOChannel *ioc);
> +
>  #endif /* QIO_CHANNEL_SOCKET_H */
> diff --git a/io/channel-socket.c b/io/channel-socket.c
> index 3b7ca924ff..cd93d7f180 100644
> --- a/io/channel-socket.c
> +++ b/io/channel-socket.c
> @@ -462,9 +462,16 @@ static void qio_channel_socket_finalize(Object *obj)
>  }
>  
>  
> +void qio_channel_socket_keep_nonblock(QIOChannel *ioc)
> +{
> +    QIOChannelSocket *sioc = QIO_CHANNEL_SOCKET(ioc);
> +    sioc->keep_nonblock = true;
> +}
> +
> +
>  #ifndef WIN32
>  static void qio_channel_socket_copy_fds(struct msghdr *msg,
> -                                        int **fds, size_t *nfds)
> +                                        int **fds, size_t *nfds, bool set_block)
>  {
>      struct cmsghdr *cmsg;
>  
> @@ -497,8 +504,9 @@ static void qio_channel_socket_copy_fds(struct msghdr *msg,
>                  continue;
>              }
>  
> -            /* O_NONBLOCK is preserved across SCM_RIGHTS so reset it */
> -            qemu_socket_set_block(fd);
> +            if (set_block) {
> +                qemu_socket_set_block(fd);
> +            }
>  
>  #ifndef MSG_CMSG_CLOEXEC
>              qemu_set_cloexec(fd);
> @@ -556,7 +564,7 @@ static ssize_t qio_channel_socket_readv(QIOChannel *ioc,
>      }
>  
>      if (fds && nfds) {
> -        qio_channel_socket_copy_fds(&msg, fds, nfds);
> +        qio_channel_socket_copy_fds(&msg, fds, nfds, !sioc->keep_nonblock);
>      }
>  
>      return ret;

If this is needed, then it should be done by defining another flag
constant to be passed to qio_channel_read*, not via a new API

 QIO_CHANNEL_READ_FLAG_FD_PRESERVE_NONBLOCKING


With regards,
Daniel
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