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.
 >> +    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?
Thanks,
-- 
Pino Toscano