Re: [Qemu-devel] [PATCH 7/7] block: dump to monitor for bdrv_snapshot_dump() and bdrv_image_info_dump()

[Luiz Capitulino <lcapitulino@redhat.com>]

On Wed, 22 May 2013 10:09:19 +0800
Wenchao Xia <xiawenc@linux.vnet.ibm.com> wrote:

> 于 2013-5-20 10:39, Wenchao Xia 写道:
> > 于 2013-5-17 20:30, Luiz Capitulino 写道:
> >> On Fri, 17 May 2013 11:30:31 +0800
> >> Wenchao Xia <xiawenc@linux.vnet.ibm.com> wrote:
> >>
> >>> 于 2013-5-16 20:17, Luiz Capitulino 写道:
> >>>> On Thu, 16 May 2013 10:22:09 +0800
> >>>> Wenchao Xia <xiawenc@linux.vnet.ibm.com> wrote:
> >>>>
> >>>>> 于 2013-5-15 20:28, Luiz Capitulino 写道:
> >>>>>> On Wed, 15 May 2013 10:10:37 +0800
> >>>>>> Wenchao Xia <xiawenc@linux.vnet.ibm.com> wrote:
> >>>>>>
> >>>>>>> 于 2013-5-6 21:22, Luiz Capitulino 写道:
> >>>>>>>> On Mon, 06 May 2013 10:09:43 +0800
> >>>>>>>> Wenchao Xia <xiawenc@linux.vnet.ibm.com> wrote:
> >>>>>>>>
> >>>>>>>>> 于 2013-5-3 10:51, Wenchao Xia 写道:
> >>>>>>>>>> 于 2013-5-2 20:02, Luiz Capitulino 写道:
> >>>>>>>>>>> On Thu, 02 May 2013 10:05:08 +0800
> >>>>>>>>>>> Wenchao Xia <xiawenc@linux.vnet.ibm.com> wrote:
> >>>>>>>>>>>
> >>>>>>>>>>>> 于 2013-4-30 3:05, Luiz Capitulino 写道:
> >>>>>>>>>>>>> On Fri, 26 Apr 2013 16:46:57 +0200
> >>>>>>>>>>>>> Stefan Hajnoczi <stefanha@gmail.com> wrote:
> >>>>>>>>>>>>>
> >>>>>>>>>>>>>> On Fri, Apr 26, 2013 at 05:31:15PM +0800, Wenchao Xia wrote:
> >>>>>>>>>>>>>>> @@ -2586,10 +2585,12 @@ void do_info_snapshots(Monitor 
> >>>>>>>>>>>>>>> *mon, const
> >>>>>>>>>>>>>>> QDict *qdict)
> >>>>>>>>>>>>>>>            }
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>            if (total > 0) {
> >>>>>>>>>>>>>>> -        monitor_printf(mon, "%s\n", bdrv_snapshot_dump(buf,
> >>>>>>>>>>>>>>> sizeof(buf), NULL));
> >>>>>>>>>>>>>>> +        bdrv_snapshot_dump(NULL);
> >>>>>>>>>>>>>>> +        monitor_printf(mon, "\n");
> >>>>>>>>>>>>>>
> >>>>>>>>>>>>>> Luiz: any issue with mixing monitor_printf(mon) and
> >>>>>>>>>>>>>> monitor_vprintf(cur_mon) calls?  I guess there was a 
> >>>>>>>>>>>>>> reason for
> >>>>>>>>>>>>>> explicitly passing mon instead of relying on cur_mon.
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> where are they being mixed?
> >>>>>>>>>>>>>
> >>>>>>>>>>>>         bdrv_snapshot_dump() used a global variable 
> >>>>>>>>>>>> "cur_mon" inside,
> >>>>>>>>>>>> instead
> >>>>>>>>>>>> of let caller pass in a explicit montior* "mon", I guess 
> >>>>>>>>>>>> that is the
> >>>>>>>>>>>> question.
> >>>>>>>>>>>
> >>>>>>>>>>> I'd have to see the code to tell, but yes, what Stefan 
> >>>>>>>>>>> described is the
> >>>>>>>>>>> best practice for the Monitor.
> >>>>>>>>>>>
> >>>>>>>>>>        I think this would not be a problem until qemu wants 
> >>>>>>>>>> more than one
> >>>>>>>>>> human monitor console, and then we may require a data 
> >>>>>>>>>> structure to tell
> >>>>>>>>>> where to output the string: stdout, *mon, or even stderr, and
> >>>>>>>>>> error_printf() also need to be changed.
> >>>>>>>>>>
> >>>>>>>>>        Luiz, what is your idea? I'd like to respin v2 if no 
> >>>>>>>>> issues for it.
> >>>>>>>>
> >>>>>>>> As I said before, I'd have to see the code to tell. But 
> >>>>>>>> answering your comment,
> >>>>>>>> the code does support multiple monitors.
> >>>>>>>>
> >>>>>>> Hi Luiz,
> >>>>>>>       Sorry to ask again, do you think method above is OK now, 
> >>>>>>> waiting for
> >>>>>>> your confirm.
> >>>>>>
> >>>>>> Can you point me to the code in question?
> >>>>>>
> >>>>> Sure, it is
> >>>>>
> >>>>> +
> >>>>> +/*
> >>>>> + * Print to current monitor if we have one, else to stdout. It is
> >>>>> similar with
> >>>>> + * error_printf().
> >>>>> + * TODO just like error_vprintf()
> >>>>> + */
> >>>>> +void message_printf(const char *fmt, ...)
> >>>>> +{
> >>>>> +    va_list ap;
> >>>>> +
> >>>>> +    va_start(ap, fmt);
> >>>>> +    if (cur_mon) {
> >>>>> +        monitor_vprintf(cur_mon, fmt, ap);
> >>>>> +    } else {
> >>>>> +        vfprintf(stdout, fmt, ap);
> >>>>> +    }
> >>>>> +    va_end(ap);
> >>>>> +}
> >>>>>
> >>>>>      This function used global variable cur_mon instead of input 
> >>>>> parameter,
> >>>>> similar to error_printf().
> >>>>
> >>>> Why do you need it? Why can't you you use error_printf() for example?
> >>>>
> >>>     error_printf() will print out to stderr in qemu-img, but stdout is
> >>> wanted for those dump info function.
> >>
> >> You can refactor the code so that you can pass a FILE *stream argument to
> >> error_vprintf() and maybe add error_printf_stream()?
> >>
> >    The name is a bit confusing, maybe qemu_printf()? Another problem is,
> > monitor have a buf[] instead of a FILE*, I think it need a structure
> > include those:
> > 
> > typdef enum QemuOutputType {
> >      QEMU_OUTPUT_TYPE_STREAM,
> >      QEMU_OUTPUT_TYPE_MONITOR,
> > } QemuOutputType;
> > 
> > typedef struct QemuOutput {
> >      QemuOutputType type;
> >      union {
> >          FILE *file;
> >          Monitor *mon;
> >      };
> > }
> > 
> >    It may brings some inconvienience to caller, but this is what I can
> > think out now.
> > 
>   Luiz, I am going to respin V2 as above, can I have you confirm on it?

I'm honestly a bit confused with what you're suggesting. I'd just respin the
patches and restart the discussion.