Re: [Qemu-devel] [PATCH for-4.0 1/3] block: continue until base is found in bdrv_freeze_backing_chain() et al

[Alberto Garcia]

On Thu 28 Mar 2019 11:33:55 AM CET, Vladimir Sementsov-Ogievskiy wrote:
>>> All three functions that handle the BdrvChild.frozen attribute walk
>>> the backing chain from 'bs' to 'base' and stop either when 'base' is
>>> found or at the end of the chain if 'base' is NULL.
>>>
>>> However if 'base' is not found then the functions return without
>>> errors as if it was NULL.
>>>
>>> This is wrong: if the caller passed an incorrect parameter that means
>>> that there is a bug in the code.
>>>
>>> Signed-off-by: Alberto Garcia <address@hidden>
>> 
>> interesting that bdrv_is_allocated_above has the same flaw. Could you
>> fix it too?
>
> However bdrv_is_allocated_above is differs from your functions, as it
> may yield.. And graph may change while it is running.. Shouldn't we
> freeze backing chain every time we want to call
> bdrv_is_allocated_above?

I think all callers of bdrv_is_allocated_above() already freeze the
chain themselves? Anyway I would not change this for 4.0 without an
actual bug.

Berto