Re: [Qemu-devel] [PATCH for-2.10 3/3] block: Add some bdrv_truncate() error messages

[Max Reitz]

On 06.03.2017 21:09, Eric Blake wrote:
> On 03/06/2017 01:54 PM, Max Reitz wrote:
>> Add missing error messages for the drivers I am comfortable to do this
>> in.
>>
>> Signed-off-by: Max Reitz <address@hidden>
>> ---
>>  block/file-posix.c | 8 +++++++-
>>  block/qcow2.c      | 2 ++
>>  block/qed.c        | 4 +++-
>>  block/raw-format.c | 2 ++
>>  4 files changed, 14 insertions(+), 2 deletions(-)
>>
>> diff --git a/block/file-posix.c b/block/file-posix.c
>> index 9d2bea730d..553213221c 100644
>> --- a/block/file-posix.c
>> +++ b/block/file-posix.c
>> @@ -1341,20 +1341,26 @@ static int raw_truncate(BlockDriverState *bs, 
>> int64_t offset, Error **errp)
>>  {
>>      BDRVRawState *s = bs->opaque;
>>      struct stat st;
>> +    int ret;
>>  
>>      if (fstat(s->fd, &st)) {
>> -        return -errno;
>> +        ret = -errno;
>> +        error_setg_errno(errp, -ret, "Failed to fstat() the file");
>> +        return ret;
>>      }
>>  
>>      if (S_ISREG(st.st_mode)) {
>>          if (ftruncate(s->fd, offset) < 0) {
>> +            /* The generic error message will be fine */
>>              return -errno;
> 
> Relying on a generic error message in the caller is awkward. I see it as
> evidence of a partial conversion if we have an interface that requires a
> return of a negative errno value to make up for when errp is not set.

I'm not sure what you mean by this exactly. I can agree that it's not
nice within a single driver. But I think it's fine to have some drivers
that generate an Error object and others that do not, as long as the
generic interface (bdrv_truncate()) masks this behavior.

>                                                                        I
> know you aren't comfortable converting all drivers, but for the drivers
> you do convert, I'd rather guarantee that ALL errors set errp.

Can do, I just felt bad that it be would exactly the same as the message
that would be generated in bdrv_truncate() anyway.

Max

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