Re: [Qemu-devel] [PATCH trivial v2] block.c: Add return value for bdrv_append_temp_snapshot() to avoid incorrect failure processing issue

[Chen Gang <gang.chen.5i5j@gmail.com>]

On 06/24/2014 10:25 AM, Fam Zheng wrote:
> On Mon, 06/23 23:28, Chen Gang wrote:
>> When failure occurs, 'ret' need be set, or may return 0 to indicate success.
> 
> s/need/needs/
> 
>> And error_propagate() also need be called only one time within a function.
> 
> s/need/needs/
> 

For a grammar in my learning, in this situation, 'need' is not a verb,
"be set" and "be called" are the verb used with passive mode.

>>
>> It is abnormal to prevent bdrv_append_temp_snapshot() return value but still
>> set errp when error occurs -- although it contents return value internally.
> 
> s/contents/has/
> 

OK, thanks, and excuse me for my poor English. If necessary I shall send
patch v2 for it.

>>
>> So let bdrv_append_temp_snapshot() internal return value outside, and let
>> all things normal, then fix the issue too.
>>
>>
>> Signed-off-by: Chen Gang <gang.chen.5i5j@gmail.com>
>> ---
>>  block.c               | 7 ++++---
>>  include/block/block.h | 2 +-
>>  2 files changed, 5 insertions(+), 4 deletions(-)
>>
>> diff --git a/block.c b/block.c
>> index 74af8d7..5e4fb60 100644
>> --- a/block.c
>> +++ b/block.c
>> @@ -1240,7 +1240,7 @@ done:
>>      return ret;
>>  }
>>  
>> -void bdrv_append_temp_snapshot(BlockDriverState *bs, int flags, Error **errp)
>> +int bdrv_append_temp_snapshot(BlockDriverState *bs, int flags, Error **errp)
>>  {
>>      /* TODO: extra byte is a hack to ensure MAX_PATH space on Windows. */
>>      char *tmp_filename = g_malloc0(PATH_MAX + 1);
>> @@ -1258,6 +1258,7 @@ void bdrv_append_temp_snapshot(BlockDriverState *bs, int flags, Error **errp)
>>      /* Get the required size from the image */
>>      total_size = bdrv_getlength(bs);
>>      if (total_size < 0) {
>> +        ret = total_size;
>>          error_setg_errno(errp, -total_size, "Could not get image size");
>>          goto out;
>>      }
>> @@ -1304,6 +1305,7 @@ void bdrv_append_temp_snapshot(BlockDriverState *bs, int flags, Error **errp)
>>  
>>  out:
>>      g_free(tmp_filename);
>> +    return ret;
>>  }
>>  
>>  static QDict *parse_json_filename(const char *filename, Error **errp)
>> @@ -1495,9 +1497,8 @@ int bdrv_open(BlockDriverState **pbs, const char *filename,
>>      /* For snapshot=on, create a temporary qcow2 overlay. bs points to the
>>       * temporary snapshot afterwards. */
>>      if (snapshot_flags) {
>> -        bdrv_append_temp_snapshot(bs, snapshot_flags, &local_err);
>> +        ret = bdrv_append_temp_snapshot(bs, snapshot_flags, &local_err);
>>          if (local_err) {
>> -            error_propagate(errp, local_err);
>>              goto close_and_fail;
>>          }
>>      }
>> diff --git a/include/block/block.h b/include/block/block.h
>> index f15b99b..7b3381c 100644
>> --- a/include/block/block.h
>> +++ b/include/block/block.h
>> @@ -217,7 +217,7 @@ int bdrv_open_image(BlockDriverState **pbs, const char *filename,
>>                      bool allow_none, Error **errp);
>>  void bdrv_set_backing_hd(BlockDriverState *bs, BlockDriverState *backing_hd);
>>  int bdrv_open_backing_file(BlockDriverState *bs, QDict *options, Error **errp);
>> -void bdrv_append_temp_snapshot(BlockDriverState *bs, int flags, Error **errp);
>> +int bdrv_append_temp_snapshot(BlockDriverState *bs, int flags, Error **errp);
> 
> Not used outside block.c, but pre-existing.
> 

Yeah, originally, I considered about it, and finally still remained it
as pre-existing.

> Reviewed-by: Fam Zheng <famz@redhat.com>
> 
Thank you for your work.

Thanks.
-- 
Chen Gang

Open, share, and attitude like air, water, and life which God blessed