On Thu, May 4, 2023 at 11:08 PM Feng zhou <zhoufeng.zf@xxxxxxxxxxxxx> wrote:
>
<...>
> ---
> kernel/bpf/helpers.c | 20 ++++++++++++++++++++
> 1 file changed, 20 insertions(+)
>
> diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
> index bb6b4637ebf2..453cbd312366 100644
> --- a/kernel/bpf/helpers.c
> +++ b/kernel/bpf/helpers.c
> @@ -2149,6 +2149,25 @@ __bpf_kfunc struct cgroup *bpf_cgroup_from_id(u64 cgid)
> return NULL;
> return cgrp;
> }
> +
> +/**
> + * bpf_task_under_cgroup - wrap task_under_cgroup_hierarchy() as a kfunc, test
> + * task's membership of cgroup ancestry.
> + * @task: the task to be tested
> + * @ancestor: possible ancestor of @task's cgroup
> + *
> + * Tests whether @task's default cgroup hierarchy is a descendant of @ancestor.
> + * It follows all the same rules as cgroup_is_descendant, and only applies
> + * to the default hierarchy.
> + */
> +__bpf_kfunc long bpf_task_under_cgroup(struct task_struct *task,
> + struct cgroup *ancestor)
> +{
> + if (unlikely(!ancestor || !task))
> + return -EINVAL;
> +
> + return task_under_cgroup_hierarchy(task, ancestor);
> +}
> #endif /* CONFIG_CGROUPS */
>
I wonder in what situation a null 'task' or 'ancestor' can be passed.
Please call out in the comment that the returned value can be a
negative error, so that writing if(bpf_task_under_cgroup()) may cause
surprising results.
Hao
