On Sun, Sep 03, 2023 at 02:27:56PM +0000, Yafang Shao wrote:
> Currently, the function task_under_cgroup_hierarchy() allows us to
> determine if a task resides exclusively within a cgroup2 hierarchy.
> Nevertheless, given the continued prevalence of cgroup1, it's useful that
> we make a minor adjustment to extend its functionality to cgroup1 as well.
> Once this modification is implemented, we will have the ability to
> effortlessly verify a task's cgroup membership within BPF programs. For
> instance, we can easily check if a task belongs to a cgroup1 directory,
> such as /sys/fs/cgroup/cpu,cpuacct/kubepods/burstable/ or
> /sys/fs/cgroup/cpu,cpuacct/kubepods/besteffort/.
>
> Signed-off-by: Yafang Shao <laoar.shao@xxxxxxxxx>
> ---
> include/linux/cgroup.h | 24 +++++++++++++++++++++---
> 1 file changed, 21 insertions(+), 3 deletions(-)
>
> diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
> index b307013..5414a2c 100644
> --- a/include/linux/cgroup.h
> +++ b/include/linux/cgroup.h
> @@ -543,15 +543,33 @@ static inline struct cgroup *cgroup_ancestor(struct cgroup *cgrp,
> * @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.
> + * It follows all the same rules as cgroup_is_descendant.
> */
> static inline bool task_under_cgroup_hierarchy(struct task_struct *task,
> struct cgroup *ancestor)
> {
> struct css_set *cset = task_css_set(task);
> + struct cgroup *cgrp;
> + bool ret = false;
> + int ssid;
> +
> + if (ancestor->root == &cgrp_dfl_root)
> + return cgroup_is_descendant(cset->dfl_cgrp, ancestor);
> +
> + for (ssid = 0; ssid < CGROUP_SUBSYS_COUNT; ssid++) {
> + if (!ancestor->subsys[ssid])
> + continue;
This looks wrong. I believe cgroup_mutex should be held to iterate.
Tejun ?
>
> - return cgroup_is_descendant(cset->dfl_cgrp, ancestor);
> + cgrp = task_css(task, ssid)->cgroup;
> + if (!cgrp)
> + continue;
> +
> + if (!cgroup_is_descendant(cgrp, ancestor))
> + return false;
> + if (!ret)
> + ret = true;
> + }
> + return ret;
> }
>
> /* no synchronization, the result can only be used as a hint */
> --
> 1.8.3.1
>
