Re: [PATCH block-5.14] Revert "block/mq-deadline: Add cgroup support"

Hello, Bart.

On Wed, Aug 11, 2021 at 11:49:10AM -0700, Bart Van Assche wrote:

Agreed that I should have Cc-ed you on the cgroup patches. But where were
you while my mq-deadline patch series was out for review? The first version
of that patch series was published on May 27 and the patch series was merged
on June 21 so there was almost one month time to post review feedback.

Regardless of where I've been, I can't really review things which
don't show up in my radar. The patches didn't even cc cgroups mailing
list. How would I know that I needed to review the patches?

Additionally, the above description is not very helpful. If it is not
allowed to add custom elements by adding more pd_stat_fn callbacks, why does
that callback even exist? Why does the cgroup core not complain if a new
policy is registered that defines a pd_stat_fn callback?

That part of the comment was on the specific fomatting that you used.
cgroup interface files follow a few styles to stay consistent and ease
parsing. Please refer to Documentation/admin-guide/cgroup-v2.rst.

You write that this isn't the right way to collect per cgroup stats. What is
the "right way"? Has this been documented somewhere?

Well, there's nothing specific to mq-deadline or any other elevator or
controller about the stats that your patch collected and showed. That
seems like a pretty straight forward sign that it likely doens't
belong there.

Thanks.

-- 
tejun