Re: [Qemu-devel] [PATCH v2] rbd: print a clear error message when write beyond EOF

[Max Reitz <mreitz@redhat.com>]

On 2014-12-11 at 10:12, Kevin Wolf wrote:
> Am 11.12.2014 um 07:25 hat Jun Li geschrieben:
>> Currently, as rbd driver do not support dynamic growth when write beyond EOF,
>> so just print a clear error message.
>>
>> Signed-off-by: Jun Li <junmuzi@gmail.com>
>> ---
>> v2:
>> Just use rbd_aio_write to realize error detection.
>> ---
>>   block/rbd.c | 4 ++++
>>   1 file changed, 4 insertions(+)
>>
>> diff --git a/block/rbd.c b/block/rbd.c
>> index 5b5a64a..710ee3e 100644
>> --- a/block/rbd.c
>> +++ b/block/rbd.c
>> @@ -661,6 +661,10 @@ static BlockAIOCB *rbd_start_aio(BlockDriverState *bs,
>>       }
>>   
>>       if (r < 0) {
>> +        if (r == -EINVAL && cmd == RBD_AIO_WRITE) {
>> +            fprintf(stderr, "Image formats that grow on demand "
>> +                            "are not supported on rbd.\n");
>> +        }
>>           goto failed_completion;
>>       }
> You can't fill up the log with messages like that. In general, if you
> use fprintf() in a function whose call can be triggered by the guest,
> you're doing it wrong.
>
> What needs to be done is to check at open time whether the configuration
> works. Max has sent a series to that end a while ago, not sure what its
> status is. I think it ended up depending on some blockdev work.

Yes, the status is that we need to remove "growable" from the BDS first.

Max