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

[Max Reitz]

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.

Max

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