[Qemu-devel] Re: [PATCH 2/3] block-nbd: fix use of protocols in backing files and nbd probing

[Anthony Liguori <aliguori@linux.vnet.ibm.com>]

On 09/16/2010 03:08 AM, Kevin Wolf wrote:
> Am 11.09.2010 16:04, schrieb Anthony Liguori:
>    
>> The use of protocols in backing_files is currently broken because of some
>> checks for adjusting relative pathnames.
>>
>> Additionally, there's a spurious read when using an nbd protocol that can be
>> quite destructive when using copy-on-read.  Potentially, this can lead to
>> probing an image file over top of NBD but this is completely wrong as NBD
>> devices are not growable.
>>
>> Signed-off-by: Anthony Liguori<aliguori@us.ibm.com>
>> ---
>> NB: this is absolutely not ideal.  A more elegant suggestion would be
>> appreciated.  I don't think NBD cleanly fits the model of a protocol as it
>> stands today.
>>
>> diff --git a/block.c b/block.c
>> index cd2ee31..a32d5dd 100644
>> --- a/block.c
>> +++ b/block.c
>> @@ -344,6 +344,12 @@ static int find_image_format(const char *filename, BlockDriver **pdrv)
>>           return ret;
>>       }
>>
>> +    if (strcmp(bs->drv->protocol_name, "nbd") == 0) {
>> +        drv = bs->drv;
>> +        bdrv_delete(bs);
>> +        goto out;
>> +    }
>>      
> Is nbd really the only protocol that behaves like this? I don't like
> hardcoding driver names in generic block layer code.
>    

I'll drop this chunk from the patch as using backing_fmt achieves the 
same goal.  The important hunk is the next one that removes assumptions 
that URIs are filenames.

Regards,

Anthony Liguori

> Kevin
>