Re: [RFC PATCH bpf-next 0/3] bpf: freeze a task cgroup from bpf

[Tejun Heo <tj@kernel.org>]

Hello, Djalal.

On Wed, Mar 27, 2024 at 11:53:22PM +0100, Djalal Harouni wrote:
> This patch series adds support to freeze the task cgroup hierarchy
> that is on a default cgroup v2 without going through kernfs interface.
> 
> For some cases we want to freeze the cgroup of a task based on some
> signals, doing so from bpf is better than user space which could be
> too late.
> 
> Planned users of this feature are: tetragon and systemd when freezing
> a cgroup hierarchy that could be a K8s pod, container, system service
> or a user session.
> 
> Patch 1: cgroup: add cgroup_freeze_no_kn() to freeze a cgroup from bpf
> Patch 2: bpf: add bpf_task_freeze_cgroup() to freeze the cgroup of a task
> Patch 3: selftests/bpf: add selftest for bpf_task_freeze_cgroup

It bothers me a bit that it's adding a dedicated interface for something
which already has a defined userspace interface. Would it be better to have
kfunc wrappers for kernel_read() and kernel_write()?

Thanks.

-- 
tejun