Re: [PATCH 1/6] qemu-img: rebase: stop when reaching EOF of old backing file

[Andrey Drobyshev <andrey.drobyshev@virtuozzo.com>]

On 6/2/23 00:18, Michael Tokarev wrote:
> 01.06.2023 22:28, Andrey Drobyshev via пишет:
>> In case when we're rebasing within one backing chain, and when target
>> image
>> is larger than old backing file, bdrv_is_allocated_above() ends up
>> setting
>> *pnum = 0.  As a result, target offset isn't getting incremented, and we
>> get stuck in an infinite for loop.  Let's detect this case and proceed
>> further down the loop body, as the offsets beyond the old backing size
>> need
>> to be explicitly zeroed.
>>
>> Signed-off-by: Andrey Drobyshev <andrey.drobyshev@virtuozzo.com>
> 
> It looks like you forgot the Reviewed-by: Denis V. Lunev here and
> in the subsequent patch.

Yes, you're right, thanks for pointing that out.

> 
> Should this be backported to -stable? Not that I've seen this issue,
> it's a quite specific and somewhat rare case..

I guess in the vast majority of cases the sizes of images within the
same backing chain are equal.  But as long as it's legal to have them
unequal, a bug remains a bug.

> 
> Thanks,
> 
> /mjt