Re: [PATCH] tools/sched_ext: scx_flatcg: Document cgroup v2 requirement

[luoliang]

On Wed, Jun 03, 2026 at 10:29:10PM -1000, Tejun Heo wrote:
> This doesn't look accurate on current kernels. BPF_MAP_TYPE_CGRP_STORAGE is
> registered unconditionally and its fd access goes through
> cgroup_v1v2_get_from_fd(), and bpf_cgroup_ancestor(), bpf_cgroup_from_id()
> and scx_bpf_task_cgroup() all take a plain struct cgroup with no v1/v2
> gating. The program should load fine on cgroup1.

You are right, thank you for the correction. I was wrong about the
v2 dependency.

> Did you actually hit a load failure, and on which kernel? cgrp_storage's
> cgroup1 access was only enabled in v6.8 by 73d9eb340d2b ("bpf: Enable
> bpf_cgrp_storage for cgroup1 non-attach case"). Before that it was cgroup2
> only, which would explain a failure on an older kernel.

I did observe a load failure on v7.1-rc3 with cgroup v1 at the time,
but I can no longer reproduce it now. It was likely caused by a local
misconfiguration or build environment issue rather than a genuine v2
dependency. I should have validated the root cause before submitting.
My apologies.

Please drop this patch.