Re: [PATCH v9 6/7] cgroup/cpuset: Update description of cpuset.cpus.partition in cgroup-v2.rst

[Tejun Heo <tj@kernel.org>]

Hello,

On Sun, Dec 05, 2021 at 01:32:19PM -0500, Waiman Long wrote:
> +	In the case of an invalid partition root, a descriptive string on
> +	why the partition is invalid is included within parentheses.
> +
> +	Almost all possible state transitions among "member", valid
> +	and invalid partition roots are allowed except from "member"
> +	to invalid partition root.

So, this part still bothers me for the following two reasons that I brought
up earlier:

* When a valid partition turns invalid, now we have a reliable way of
  discovering what exactly caused the transition. However, when a user now
  fails to turn a member into partition, all they get is -EINVAL and there's
  no way to discover why it failed and the failure conditions that -EINVAL
  represents aren't simple.

* In an automated configuration scenarios, this operation mode may be
  difficult to make reliable and lead to sporadic failures which can be
  tricky to track down. The core problem is that whether a given operation
  succeeds or not may depend on external states (CPU on/offline) which may
  change asynchronously in a way that the configuring entity doesn't have
  any control over.

It's true that both are existing problems with the current partition
interface and given that this is a pretty spcialized feature, this can be
okay. Michal, what are your thoughts?

Thanks.

-- 
tejun