Re: [PATCH v5 21/45] block: add bdrv_try_set_aio_context_tran transaction action

[Hanna Reitz]

On 09.06.22 16:56, Vladimir Sementsov-Ogievskiy wrote:
> On 6/8/22 14:49, Hanna Reitz wrote:
> > On 30.03.22 23:28, Vladimir Sementsov-Ogievskiy wrote:
> > > To be used in further commit.
> > >
> > > Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@openvz.org>
> > > ---
> > >   block.c | 48 ++++++++++++++++++++++++++++++++++++++++++++++++
> > >   1 file changed, 48 insertions(+)
> >
> > Looking at bdrv_child_try_set_aio_context(), it looks like 
> > bdrv_can_set_aio_context() were supposed to be the .prepare action, 
> > and bdrv_set_aio_context_ignore() should be the .commit action.  Can 
> > we not use it that way?
>
>
> The difference is that we want the whole action be done in .prepare 
> stage, not only the check. It's generally better: when do several 
> actions in a transaction, actions usually depend on result of previous 
> actions.

Ah, yes.

> And I think it's necessary for graph update. Graph relations are 
> changed during other actions .prepare phases, so I can't imagine how 
> to postpone aio-context update to .commit phase.

OK, sounds good.

> But I agree, that having both _can_ / _set_  and *tran APIs don't look 
> good. May be we can refactor it.. But not in this series I think)