> diff --git a/kernel/cgroup/bpf_cgroup.c b/kernel/cgroup/bpf_cgroup.c
> index cd28c838dc7b..e253633e8278 100644
> --- a/kernel/cgroup/bpf_cgroup.c
> +++ b/kernel/cgroup/bpf_cgroup.c
> @@ -8,12 +8,50 @@
> #include <linux/bpf.h>
> #include <linux/btf_ids.h>
> #include <linux/cgroup.h>
> +#include <linux/rcupdate.h>
>
> +#ifdef CONFIG_CGROUP_SCHED
> #include "../sched/sched.h"
> +#endif
>
> -#ifdef CONFIG_CGROUP_SCHED
> __bpf_kfunc_start_defs();
>
> +/**
> + * bpf_cgroup_css - Get a reference to one controller's css
> + * @cgrp: cgroup to look in
> + * @ssid: controller ID
> + *
> + * The returned css must be released with bpf_css_release().
> + *
> + * Return: The referenced css, or NULL.
> + */
> +__bpf_kfunc struct cgroup_subsys_state *
> +bpf_cgroup_css(struct cgroup *cgrp, int ssid)
> +{
> + struct cgroup_subsys_state *css;
> +
> + if (unlikely(ssid < 0 || ssid >= CGROUP_SUBSYS_COUNT))
> + return NULL;
> +
> + rcu_read_lock();
> + css = rcu_dereference(cgrp->subsys[ssid]);
> + if (css && !css_tryget(css))
> + css = NULL;
> + rcu_read_unlock();
> +
> + return css;
> +}
> +
> +/**
> + * bpf_css_release - Release a css reference
> + * @css: css to release
> + */
> +__bpf_kfunc void bpf_css_release(struct cgroup_subsys_state *css)
> +{
> + css_put(css);
> +}
> +
> +#ifdef CONFIG_CGROUP_SCHED
[ ... ]
> @@ -30,29 +68,33 @@ bpf_css_to_task_group(struct cgroup_subsys_state *css)
>
> return container_of(css, struct task_group, css);
> }
> +#endif /* CONFIG_CGROUP_SCHED */
>
> __bpf_kfunc_end_defs();
>
> -BTF_KFUNCS_START(bpf_cpu_cgroup_kfunc_ids)
> +BTF_KFUNCS_START(bpf_cgroup_kfunc_ids)
> +BTF_ID_FLAGS(func, bpf_cgroup_css, KF_ACQUIRE | KF_RCU | KF_RET_NULL)
> +BTF_ID_FLAGS(func, bpf_css_release, KF_RELEASE)
> +#ifdef CONFIG_CGROUP_SCHED
> BTF_ID_FLAGS(func, bpf_css_to_task_group,
> KF_RCU | KF_RCU_PROTECTED | KF_RET_NULL)
> -BTF_KFUNCS_END(bpf_cpu_cgroup_kfunc_ids)
> +#endif
> +BTF_KFUNCS_END(bpf_cgroup_kfunc_ids)
>
> -static const struct btf_kfunc_id_set bpf_cpu_cgroup_kfunc_set = {
> +static const struct btf_kfunc_id_set bpf_cgroup_kfunc_set = {
> .owner = THIS_MODULE,
> - .set = &bpf_cpu_cgroup_kfunc_ids,
> + .set = &bpf_cgroup_kfunc_ids,
> };
>
> -static int __init bpf_cpu_cgroup_kfunc_init(void)
> +static int __init bpf_cgroup_kfunc_init(void)
> {
> int err;
>
> err = register_btf_kfunc_id_set(BPF_PROG_TYPE_UNSPEC,
> - &bpf_cpu_cgroup_kfunc_set);
> + &bpf_cgroup_kfunc_set);
> if (err)
> - pr_warn("error while registering cpu cgroup kfuncs: %d\n", err);
> + pr_warn("error while registering cgroup kfuncs: %d\n", err);
>
> return err;
> }
> -late_initcall(bpf_cpu_cgroup_kfunc_init);
> -#endif /* CONFIG_CGROUP_SCHED */
> +late_initcall(bpf_cgroup_kfunc_init);
This isn't a bug, but the patch adds two controller-agnostic kfuncs
(bpf_cgroup_css and bpf_css_release) in kernel/cgroup/bpf_cgroup.c, along
with a three-way rename (bpf_cpu_cgroup_kfunc_ids to bpf_cgroup_kfunc_ids)
and an ifdef restructure of the whole file.
The immediately preceding commit in this series (382c3bd4 "cgroup: add BPF
kfuncs to read a cpu cgroup's stats") already touched this same file under
a "cgroup:" prefix.
Would it be worth splitting the generic css acquire/release and the rename
into a separate "cgroup:" patch, so this one stays scoped to the block
changes?
---
AI reviewed your patch. Please fix the bug or email reply why it's not a bug.
See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md
CI run summary: https://github.com/kernel-patches/bpf/actions/runs/32419919743
