Re: [Qemu-block] [PATCH for-3.1 v10 05/31] block: Respect backing bs in bdrv_refresh_filename

[Alberto Garcia]

On Wed 29 Aug 2018 11:44:52 AM CEST, Max Reitz wrote:
> On 2018-08-28 15:26, Alberto Garcia wrote:
>> On Thu 09 Aug 2018 11:35:02 PM CEST, Max Reitz wrote:
>>> +    backing_overridden = bdrv_backing_overridden(bs);
>>> +
>>> +    if (bs->open_flags & BDRV_O_NO_IO) {
>>> +        /* Without I/O, the backing file does not change anything.
>>> +         * Therefore, in such a case (primarily qemu-img), we can
>>> +         * pretend the backing file has not been overridden even if
>>> +         * it technically has been. */
>>> +        backing_overridden = false;
>>> +    }
>> 
>> What is this for?
>
> qemu-img info opens files with BDRV_O_NO_BACKING.  Without this check,
> you'd get a json:{} filename with "backing": null.

Ah, I see.

Reviewed-by: Alberto Garcia <address@hidden>

Berto