[1/2] config: qemu_config_parse() return number of config groups

Uh, I totally forgot about this series.  My apologies...

Eduardo Habkost <ehabkost@redhat.com> writes:

> Change qemu_config_parse() to return the number of config groups
> in success and -EINVAL on error. This will allow callers of
> qemu_config_parse() to check if something was really loaded from
> the config file.
>
> All existing callers of qemu_config_parse() and
> qemu_read_config_file() only check if the return value was
> negative, so the change shouldn't affect them.

Two of them:

* read_config() maps negative value to -EINVAL.  Callers:

  - blkdebug_open() passes it on.  As a .bdrv_file_open() method, it's
    supposed to return -errno on failure.  Good.

* qemu_read_config_file() maps non-zero value to -EINVAL.  Callers:

  - qemu_read_default_config_file() maps -EINVAL to zero.  WTF?

  - main() passes sterror(EINVAL) to error_report().  Good.

Also: qemu_config_parse() reports errors with error_report().  Let's
have another look at its callers:

* read_config() has an Error ** parameter.  Bad.  Care to convert the
  sucker to Error?

* qemu_read_config_file() doesn't report errors.  Callers:

  - qemu_read_default_config_file() doesn't report errors.  Its called
    by main(), and ...

  - main() reports with error_report().  Good.

>
> Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
> ---
>  util/qemu-config.c | 15 +++++++--------
>  1 file changed, 7 insertions(+), 8 deletions(-)
>
> diff --git a/util/qemu-config.c b/util/qemu-config.c
> index 5527100a01..560c201bd3 100644
> --- a/util/qemu-config.c
> +++ b/util/qemu-config.c
> @@ -379,6 +379,7 @@ void qemu_config_write(FILE *fp)
>      }
>  }
>  
> +/* Returns number of config groups on success, -errno on error */
>  int qemu_config_parse(FILE *fp, QemuOptsList **lists, const char *fname)
>  {
>      char line[1024], group[64], id[64], arg[64], value[1024];
> @@ -386,7 +387,8 @@ int qemu_config_parse(FILE *fp, QemuOptsList **lists, const char *fname)
>      QemuOptsList *list = NULL;
>      Error *local_err = NULL;
>      QemuOpts *opts = NULL;
> -    int res = -1, lno = 0;
> +    int res = -EINVAL, lno = 0;
> +    int count = 0;
>  
>      loc_push_none(&loc);
>      while (fgets(line, sizeof(line), fp) != NULL) {
> @@ -407,6 +409,7 @@ int qemu_config_parse(FILE *fp, QemuOptsList **lists, const char *fname)
>                  goto out;
>              }
>              opts = qemu_opts_create(list, id, 1, NULL);
> +            count++;
>              continue;
>          }
>          if (sscanf(line, "[%63[^]]]", group) == 1) {
> @@ -417,6 +420,7 @@ int qemu_config_parse(FILE *fp, QemuOptsList **lists, const char *fname)
>                  goto out;
>              }
>              opts = qemu_opts_create(list, NULL, 0, &error_abort);
> +            count++;
>              continue;
>          }
>          value[0] = '\0';
> @@ -441,7 +445,7 @@ int qemu_config_parse(FILE *fp, QemuOptsList **lists, const char *fname)
>          error_report("error reading file");
>          goto out;
>      }
> -    res = 0;
> +    res = count;
>  out:
>      loc_pop(&loc);
>      return res;
> @@ -458,12 +462,7 @@ int qemu_read_config_file(const char *filename)
>  
>      ret = qemu_config_parse(f, vm_config_groups, filename);
>      fclose(f);
> -
> -    if (ret == 0) {
> -        return 0;
> -    } else {
> -        return -EINVAL;
> -    }
> +    return ret;
>  }
>  
>  static void config_parse_qdict_section(QDict *options, QemuOptsList *opts,

I think this mapping to -EINVAL is also superfluous now:

On Mon, Feb 27, 2017 at 06:59:51PM +0100, Markus Armbruster wrote:
> Uh, I totally forgot about this series.  My apologies...
> 
> Eduardo Habkost <ehabkost@redhat.com> writes:
> 
> > Change qemu_config_parse() to return the number of config groups
> > in success and -EINVAL on error. This will allow callers of
> > qemu_config_parse() to check if something was really loaded from
> > the config file.
> >
> > All existing callers of qemu_config_parse() and
> > qemu_read_config_file() only check if the return value was
> > negative, so the change shouldn't affect them.
> 
> Two of them:
> 
> * read_config() maps negative value to -EINVAL.  Callers:
> 
>   - blkdebug_open() passes it on.  As a .bdrv_file_open() method, it's
>     supposed to return -errno on failure.  Good.
> 
> * qemu_read_config_file() maps non-zero value to -EINVAL.  Callers:
> 
>   - qemu_read_default_config_file() maps -EINVAL to zero.  WTF?

qemu_read_config_file() maps -ENOENT to zero, not -EINVAL. It
will ignore the error only if the default config file doesn't
exist (if fopen() sets errno to ENOENT).

> 
>   - main() passes sterror(EINVAL) to error_report().  Good.
> 
> Also: qemu_config_parse() reports errors with error_report().  Let's
> have another look at its callers:
> 
> * read_config() has an Error ** parameter.  Bad.  Care to convert the
>   sucker to Error?

I can do it in a separate patch, unless you believe it must be
done by this patch patch in a single step.

> 
> * qemu_read_config_file() doesn't report errors.  Callers:
> 
>   - qemu_read_default_config_file() doesn't report errors.  Its called
>     by main(), and ...

This means fopen() errors won't get reported. Good catch. I will
send a separate fix.

> 
>   - main() reports with error_report().  Good.
> 
[...]
> 
> I think this mapping to -EINVAL is also superfluous now:
> 
> diff --git a/block/blkdebug.c b/block/blkdebug.c
> index 6117ce5..fbefa9e 100644
> --- a/block/blkdebug.c
> +++ b/block/blkdebug.c
> @@ -252,7 +252,6 @@ static int read_config(BDRVBlkdebugState *s, const char *filename,
>          ret = qemu_config_parse(f, config_groups, filename);
>          if (ret < 0) {
>              error_setg(errp, "Could not parse blkdebug config file");
> -            ret = -EINVAL;
>              goto fail;

Good catch. I will squash it into the patch.

Eduardo Habkost <ehabkost@redhat.com> writes:

> On Mon, Feb 27, 2017 at 06:59:51PM +0100, Markus Armbruster wrote:
>> Uh, I totally forgot about this series.  My apologies...
>> 
>> Eduardo Habkost <ehabkost@redhat.com> writes:
>> 
>> > Change qemu_config_parse() to return the number of config groups
>> > in success and -EINVAL on error. This will allow callers of
>> > qemu_config_parse() to check if something was really loaded from
>> > the config file.
>> >
>> > All existing callers of qemu_config_parse() and
>> > qemu_read_config_file() only check if the return value was
>> > negative, so the change shouldn't affect them.
>> 
>> Two of them:
>> 
>> * read_config() maps negative value to -EINVAL.  Callers:
>> 
>>   - blkdebug_open() passes it on.  As a .bdrv_file_open() method, it's
>>     supposed to return -errno on failure.  Good.
>> 
>> * qemu_read_config_file() maps non-zero value to -EINVAL.  Callers:
>> 
>>   - qemu_read_default_config_file() maps -EINVAL to zero.  WTF?
>
> qemu_read_config_file() maps -ENOENT to zero, not -EINVAL. It
> will ignore the error only if the default config file doesn't
> exist (if fopen() sets errno to ENOENT).

Crosseyed reviewer syndrome...

>>   - main() passes sterror(EINVAL) to error_report().  Good.
>> 
>> Also: qemu_config_parse() reports errors with error_report().  Let's
>> have another look at its callers:
>> 
>> * read_config() has an Error ** parameter.  Bad.  Care to convert the
>>   sucker to Error?
>
> I can do it in a separate patch, unless you believe it must be
> done by this patch patch in a single step.

It *should* be a separate patch.

>> 
>> * qemu_read_config_file() doesn't report errors.  Callers:
>> 
>>   - qemu_read_default_config_file() doesn't report errors.  Its called
>>     by main(), and ...
>
> This means fopen() errors won't get reported. Good catch. I will
> send a separate fix.
>
>> 
>>   - main() reports with error_report().  Good.
>> 
> [...]
>> 
>> I think this mapping to -EINVAL is also superfluous now:
>> 
>> diff --git a/block/blkdebug.c b/block/blkdebug.c
>> index 6117ce5..fbefa9e 100644
>> --- a/block/blkdebug.c
>> +++ b/block/blkdebug.c
>> @@ -252,7 +252,6 @@ static int read_config(BDRVBlkdebugState *s, const char *filename,
>>          ret = qemu_config_parse(f, config_groups, filename);
>>          if (ret < 0) {
>>              error_setg(errp, "Could not parse blkdebug config file");
>> -            ret = -EINVAL;
>>              goto fail;
>
> Good catch. I will squash it into the patch.

Looking forward to v2 :)