Date:   Thu, 16 Dec 2021 10:28:37 +0100
From:   Michal =?iso-8859-1?Q?Koutn=FD?= <mkoutny@suse.com>
To:     Waiman Long <longman@redhat.com>
Cc:     Tejun Heo <tj@kernel.org>, Zefan Li <lizefan.x@bytedance.com>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Jonathan Corbet <corbet@lwn.net>,
        Shuah Khan <shuah@kernel.org>, cgroups@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org,
        linux-kselftest@vger.kernel.org,
        Andrew Morton <akpm@linux-foundation.org>,
        Roman Gushchin <guro@fb.com>, Phil Auld <pauld@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Juri Lelli <juri.lelli@redhat.com>,
        Frederic Weisbecker <frederic@kernel.org>,
        Marcelo Tosatti <mtosatti@redhat.com>
Subject: Re: [PATCH v9 3/7] cgroup/cpuset: Refining features and constraints
 of a partition
Message-ID: <20211216092837.GB46450@blackbody.suse.cz>
References: <20211205183220.818872-1-longman@redhat.com>
 <20211205183220.818872-4-longman@redhat.com>
 <20211215144944.GE16798@blackbody.suse.cz>
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On Wed, Dec 15, 2021 at 11:29:41AM -0500, Waiman Long <longman@redhat.com> wrote:
> There are additional checks for the member to partition transition which
> requires that the target cpuset shouldn't have child cpuset.

Ah, I forgot the transition condition no. 4 will apply here. Clear.

So, currently full bottom up + top down walk is needed in (rare?) case
the switch from root partition to member and back.

> That prevents the recovering of a invalid partition root under a
> member cpuset. We could certainly remove that restriction by adding
> additional code as well as additional tests to verify it works. I
> haven't done that simply to avoid adding more complexity to the
> current code.

I agree this restriction can be lifted later independently when the rest
settles.  (It's not so different from controllers disabling on the
unified hierarchy after all.)


Thanks,
Michal