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 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()?