Hello Peter, On Thu, Jul 7, 2022 at 2:47 PM Peter Xu <pet...@redhat.com> wrote: > > Hi, Leo, > > 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 <leob...@redhat.com> > > --- > > io/channel-socket.c | 8 +++++++- > > 1 file changed, 7 insertions(+), 1 deletion(-) > > > > 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) { > > I think I asked this in the downstream review but didn't get a > response.. shouldn't this check be "queued == sent"?
This is just supposed to skip flush if nothing was queued for sending. queued == sent is tested bellow in the while part. Without this, the function could return 1 if nothing was sent with zero-copy, and it would be confusing, because the QIOChannel API says 1 should be returned only if all zero-copy sends fell back to copying. Best regards, Leo > > > + 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 > > > > -- > Peter Xu >