Re: [PATCH v3 1/3] QIOChannelSocket: Fix zero-copy flush returning code 1 when nothing sent

[Juan Quintela <quintela@redhat.com>]

Daniel P. Berrangé <berrange@redhat.com> wrote:
> On Mon, Jul 04, 2022 at 05:23:13PM -0300, Leonardo Bras wrote:
>> If flush is called when no buffer was sent with MSG_ZEROCOPY, it currently
>> returns 1. This return code should be used only when Linux fails to use
>> MSG_ZEROCOPY on a lot of sendmsg().
>> 
>> Fix this by returning early from flush if no sendmsg(...,MSG_ZEROCOPY)
>> was attempted.
>> 
>> Fixes: 2bc58ffc2926 ("QIOChannelSocket: Implement io_writev zero copy flag & io_flush for CONFIG_LINUX")
>> Signed-off-by: Leonardo Bras <leobras@redhat.com>
>> ---
>>  io/channel-socket.c | 8 +++++++-
>>  1 file changed, 7 insertions(+), 1 deletion(-)
>
> Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
>
> And if this merges via migration maintainers' tree
>
> Acked-by: Daniel P. Berrangé <berrange@redhat.com>

Reviewed-by: Juan Quintela <quintela@redhat.com>

I will add this on the next PULLL request.

Thanks.


>> 
>> diff --git a/io/channel-socket.c b/io/channel-socket.c
>> index 4466bb1cd4..698c086b70 100644
>> --- a/io/channel-socket.c
>> +++ b/io/channel-socket.c
>> @@ -716,12 +716,18 @@ static int qio_channel_socket_flush(QIOChannel *ioc,
>>      struct cmsghdr *cm;
>>      char control[CMSG_SPACE(sizeof(*serr))];
>>      int received;
>> -    int ret = 1;
>> +    int ret;
>> +
>> +    if (!sioc->zero_copy_queued) {
>> +        return 0;
>> +    }
>>  
>>      msg.msg_control = control;
>>      msg.msg_controllen = sizeof(control);
>>      memset(control, 0, sizeof(control));
>>  
>> +    ret = 1;
>> +
>>      while (sioc->zero_copy_sent < sioc->zero_copy_queued) {
>>          received = recvmsg(sioc->fd, &msg, MSG_ERRQUEUE);
>>          if (received < 0) {
>> -- 
>> 2.36.1
>> 
>
> With regards,
> Daniel