[Libguestfs] [PATCH] New API: btrfs_device_stats

[Cao jin]

Hi, Pino

在 2015年06月17日 23:37, Pino Toscano 写道:
> Hi,
>
> On Wednesday 17 June 2015 10:12:59 Cao jin wrote:
>>>> @@ -2083,3 +2083,72 @@ do_btrfs_image (char *const *sources, const char *image,
>>>>
>>>>      return 0;
>>>>    }
>>>> +
>>>> +char **
>>>> +do_btrfs_device_stats (const char *path, int zero)
>>>> +{
>>>> +  const size_t MAX_ARGS = 64;
>>>> +  const char *argv[MAX_ARGS];
>>>> +  size_t i = 0;
>>>> +  CLEANUP_FREE char *buf = NULL;
>>>> +  CLEANUP_FREE char *err = NULL;
>>>> +  CLEANUP_FREE char *out = NULL;
>>>> +  char *p, *key = NULL, *value = NULL;
>>>> +  DECLARE_STRINGSBUF (ret);
>>>
>>> 'ret' is leaked if returning before "return ret.argv".
>>>
>>
>> yup...will fix this. see some other APIs have the same problem.
>
> I will send something to help with these issues, so no need to change
> this for now.
>
OK
>>>> +    if (add_string (&ret, key) == -1)
>>>> +      return NULL;
>>>> +
>>>> +    if (add_string (&ret, value) == -1)
>>>> +      return NULL;
>>>> +
>>>> +    p = analyze_line(p, &key, &value, ' ');
>>>> +  }
>>>
>>> This means that the return "hash" will have keys like:
>>>     [/dev/sda].write_io_errs
>>> ? Wouldn't it better to just return the name of the attribute, i.e.
>>>     write_io_errs
>>> ?
>>
>> In the condition that the btrfs have multi devices, its original output
>> is going to this way:
>>     [/dev/sda].write_io_errs   0
>>     [/dev/sda].read_io_errs    0
>>     [/dev/sda].flush_io_errs   0
>>     [/dev/sda].corruption_errs 0
>>     [/dev/sda].generation_errs 0
>>     [/dev/sdb].write_io_errs   0
>>     [/dev/sdb].read_io_errs    0
>>     [/dev/sdb].flush_io_errs   0
>>     [/dev/sdb].corruption_errs 0
>>     [/dev/sdb].generation_errs 0
>>     [/dev/sdc]...
>>     [/dev/sdc]...
>>     [/dev/sdc]...
>>     [/dev/sdc]...
>>     ...
>> So. I think the [/dev/sd..] is necessary, how to think?
>
> Possibly, but the user (as in caller for this API) still need to do
> some kind of parsing; given that you are basically copying bits from
> the btrfs output, they might change breaking users.
>
> Speaking of this: you said that you have a colleague working on
> btrfs-progs? What about suggesting to create some machine-parseable
> output (csv, xml, yaml, json, whatever) so extracting the results of
> btrfs tools is a lot more easy?
>

Yes, I forward your suggestion and consult him, the result is not 
surprised:( Here is what I learned from him:
   For the btrfs-progs cmds who output strings, the output are plain, 
don`t have patterns. Seen some guys who want a formatted output, they do 
a filter by themself, it not reasonable to ask btrfs-progs to output 
formatted strings.

What`s your opinion about the output pattern? I can try to implement it.

> Thanks,
>

-- 
Yours Sincerely,

Cao Jin