[RFC PATCH bpf-next 2/8] cgroup: Add new helpers for cgroup1 hierarchy

Yafang Shao
2023-10-07T14:03:21Z

Two new helpers are added for cgroup1 hierarchy:

- task_cgroup1_id_within_hierarchy
Retrieves the associated cgroup ID of a task within a specific cgroup1
hierarchy. The cgroup1 hierarchy is identified by its hierarchy ID.
- task_ancestor_cgroup1_id_within_hierarchy
Retrieves the associated ancestor cgroup ID of a task whithin a
specific cgroup1 hierarchy. The specific ancestor level is determined by
its ancestor level.

These helper functions have been added to facilitate the tracing of tasks
within a particular container or cgroup in BPF programs. It's important to
note that these helpers are designed specifically for cgroup1.

Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
---
include/linux/cgroup.h | 9 ++++-
kernel/cgroup/cgroup-internal.h | 2 -
kernel/cgroup/cgroup-v1.c | 67 +++++++++++++++++++++++++++++++++
3 files changed, 75 insertions(+), 3 deletions(-)

diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index b307013b9c6c..65bde6eb41ef 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -71,6 +71,8 @@ struct css_task_iter {
extern struct file_system_type cgroup_fs_type;
extern struct cgroup_root cgrp_dfl_root;
extern struct css_set init_css_set;
+extern struct list_head cgroup_roots;
+extern spinlock_t css_set_lock;

#define SUBSYS(_x) extern struct cgroup_subsys _x ## _cgrp_subsys;
#include <linux/cgroup_subsys.h>
@@ -159,6 +161,8 @@ void css_task_iter_start(struct cgroup_subsys_state *css, unsigned int flags,
struct css_task_iter *it);
struct task_struct *css_task_iter_next(struct css_task_iter *it);
void css_task_iter_end(struct css_task_iter *it);
+struct cgroup *task_cgroup_from_root(struct task_struct *task,
+ struct cgroup_root *root);

/**
* css_for_each_child - iterate through children of a css
@@ -388,7 +392,6 @@ static inline void cgroup_unlock(void)
* as locks used during the cgroup_subsys::attach() methods.
*/
#ifdef CONFIG_PROVE_RCU
-extern spinlock_t css_set_lock;
#define task_css_set_check(task, __c) \
rcu_dereference_check((task)->cgroups, \
rcu_read_lock_sched_held() || \
@@ -855,4 +858,8 @@ static inline void cgroup_bpf_put(struct cgroup *cgrp) {}

#endif /* CONFIG_CGROUP_BPF */

+u64 task_cgroup1_id_within_hierarchy(struct task_struct *tsk, int hierarchy_id);
+u64 task_ancestor_cgroup1_id_within_hierarchy(struct task_struct *tsk, int hierarchy_id,
+ int ancestor_level);
+
#endif /* _LINUX_CGROUP_H */
diff --git a/kernel/cgroup/cgroup-internal.h b/kernel/cgroup/cgroup-internal.h
index c56071f150f2..2c32a80c1334 100644
--- a/kernel/cgroup/cgroup-internal.h
+++ b/kernel/cgroup/cgroup-internal.h
@@ -164,9 +164,7 @@ struct cgroup_mgctx {
#define DEFINE_CGROUP_MGCTX(name) \
struct cgroup_mgctx name = CGROUP_MGCTX_INIT(name)

-extern spinlock_t css_set_lock;
extern struct cgroup_subsys *cgroup_subsys[];
-extern struct list_head cgroup_roots;

/* iterate across the hierarchies */
#define for_each_root(root) \
diff --git a/kernel/cgroup/cgroup-v1.c b/kernel/cgroup/cgroup-v1.c
index c487ffef6652..18064de0a883 100644
--- a/kernel/cgroup/cgroup-v1.c
+++ b/kernel/cgroup/cgroup-v1.c
@@ -1263,6 +1263,73 @@ int cgroup1_get_tree(struct fs_context *fc)
return ret;
}

+/**
+ * task_cgroup_id_within_hierarchy - Retrieves the associated cgroup ID from
+ * a task within a specific cgroup1 hierarchy.
+ * @task: The task to be tested
+ * @hierarchy_id: The hierarchy ID of a cgroup1
+ *
+ * We limit it to cgroup1 only.
+ */
+u64 task_cgroup1_id_within_hierarchy(struct task_struct *tsk, int hierarchy_id)
+{
+ struct cgroup_root *root;
+ struct cgroup *cgrp;
+ u64 cgid = 0;
+
+ spin_lock_irq(&css_set_lock);
+ list_for_each_entry(root, &cgroup_roots, root_list) {
+ /* cgroup1 only*/
+ if (root == &cgrp_dfl_root)
+ continue;
+ if (root->hierarchy_id != hierarchy_id)
+ continue;
+ cgrp = task_cgroup_from_root(tsk, root);
+ WARN_ON_ONCE(!cgrp);
+ cgid = cgroup_id(cgrp);
+ break;
+ }
+ spin_unlock_irq(&css_set_lock);
+ return cgid;
+}
+
+/**
+ * task_ancestor_cgroup_id_within_hierarchy - Retrieves the associated ancestor
+ * cgroup ID from a task within a specific cgroup1 hierarchy.
+ * @task: The task to be tested
+ * @hierarchy_id: The hierarchy ID of a cgroup1
+ * @ancestor_level: level of ancestor to find starting from root
+ *
+ * We limit it to cgroup1 only.
+ */
+u64 task_ancestor_cgroup1_id_within_hierarchy(struct task_struct *tsk, int hierarchy_id,
+ int ancestor_level)
+{
+ struct cgroup *cgrp, *ancestor;
+ struct cgroup_root *root;
+ u64 cgid = 0;
+
+ spin_lock_irq(&css_set_lock);
+ list_for_each_entry(root, &cgroup_roots, root_list) {
+ /* cgroup1 only*/
+ if (root == &cgrp_dfl_root)
+ continue;
+ if (root->hierarchy_id != hierarchy_id)
+ continue;
+
+ cgrp = task_cgroup_from_root(tsk, root);
+ WARN_ON_ONCE(!cgrp);
+ ancestor = cgroup_ancestor(cgrp, ancestor_level);
+ if (!ancestor)
+ break;
+
+ cgid = cgroup_id(ancestor);
+ break;
+ }
+ spin_unlock_irq(&css_set_lock);
+ return cgid;
+}
+
static int __init cgroup1_wq_init(void)
{
/*
--
2.30.1 (Apple Git-130)