Re: [PATCH v5 10/31] block.c: modify .attach and .detach callbacks of child_of_bds

[Hanna Reitz <hreitz@redhat.com>]

On 16.12.21 17:05, Emanuele Giuseppe Esposito wrote:
>
>
> On 16/12/2021 15:57, Hanna Reitz wrote:
>> On 24.11.21 07:43, Emanuele Giuseppe Esposito wrote:
>>> According to the assertions put in the previous patch, we should
>>> first drain and then modify the ->children list. In this way
>>> we prevent other iothreads to read the list while it is being
>>> updated.
>>>
>>> In this case, moving the drain won't cause any harm, because
>>> child is a parameter of the drain function so it will still be
>>> included in the operation, despite not being in the list.
>>
>> Sounds good.
>
> Uhm.. I don't think this is useful at all. I was thinking to drop this 
> patch in v6.
>
> My plans on subtree drains, ->children and ->parent lists are 
> explained in "Removal of Aiocontext lock and usage of subtree drains 
> in aborted transactions"
>
> https://patchew.org/QEMU/20211213104014.69858-1-eesposit@redhat.com/
>
> And as I say there, commit d736f119da makes sure that it is safe to 
> modify the graph even side a bdrv_subtree_drained_begin/end() section.
> So this should be unnecessary.

Sounds good, too. :)

Hanna