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

[Wenchao Xia <xiawenc@linux.vnet.ibm.com>]

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.

-- 
Best Regards

Wenchao Xia