Re: [PATCH v2 1/2] blk-iocost: add refcounting for iocg

[Yu Kuai]

Hi,

在 2023/01/06 2:32, Tejun Heo 写道:
> On Thu, Jan 05, 2023 at 09:14:07AM +0800, Yu Kuai wrote:
> > 1) is related to blkg, while 2) is not, hence refcnting from blkg can't
> > fix the problem. refcnting from blkcg_policy_data should be ok, but I
> > see that bfq already has the similar refcnting, while other policy
> > doesn't require such refcnting.
>
> Hmm... taking a step back, wouldn't this be solved by moving the first part
> of ioc_pd_free() to pd_offline_fn()? The ordering is strictly defined there,
> right?

Moving first part to pd_offline_fn() has some requirements, like what I
did in the other thread:

iocg can be activated again after pd_offline_fn(), which is possible
because bio can be dispatched when cgroup is removed. I tried to avoid
that by:

1) dispatch all throttled bio io ioc_pd_offline()
2) don't throttle bio after ioc_pd_offline()

However, you already disagreed with that. 😔

Thanks,
Kuai

> Thanks.
>
> --
> tejun
> .