netdev - [RFC PATCH bpf-next 12/15] mm, memcg: Add new helper get_obj_cgroup_from

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Message-Id: <20220729152316.58205-13-laoar.shao@gmail.com>
Date:   Fri, 29 Jul 2022 15:23:13 +0000
From:   Yafang Shao <laoar.shao@...il.com>
To:     ast@...nel.org, daniel@...earbox.net, andrii@...nel.org,
        kafai@...com, songliubraving@...com, yhs@...com,
        john.fastabend@...il.com, kpsingh@...nel.org, sdf@...gle.com,
        haoluo@...gle.com, jolsa@...nel.org, hannes@...xchg.org,
        mhocko@...nel.org, roman.gushchin@...ux.dev, shakeelb@...gle.com,
        songmuchun@...edance.com, akpm@...ux-foundation.org
Cc:     netdev@...r.kernel.org, bpf@...r.kernel.org, linux-mm@...ck.org,
        Yafang Shao <laoar.shao@...il.com>
Subject: [RFC PATCH bpf-next 12/15] mm, memcg: Add new helper get_obj_cgroup_from_cgroup

Introduce new helper get_obj_cgroup_from_cgroup() to get obj_cgroup from
a specific cgroup.

Signed-off-by: Yafang Shao <laoar.shao@...il.com>
---
 include/linux/memcontrol.h |  1 +
 mm/memcontrol.c            | 41 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 42 insertions(+)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 2f0a611f12e5..901a9219fe9a 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -1713,6 +1713,7 @@ bool mem_cgroup_kmem_disabled(void);
 int __memcg_kmem_charge_page(struct page *page, gfp_t gfp, int order);
 void __memcg_kmem_uncharge_page(struct page *page, int order);
 
+struct obj_cgroup *get_obj_cgroup_from_cgroup(struct cgroup *cgrp);
 struct obj_cgroup *get_obj_cgroup_from_current(void);
 struct obj_cgroup *get_obj_cgroup_from_page(struct page *page);
 
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 618c366a2f07..762cffae0320 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2908,6 +2908,47 @@ static struct obj_cgroup *__get_obj_cgroup_from_memcg(struct mem_cgroup *memcg)
 	return objcg;
 }
 
+static struct obj_cgroup *get_obj_cgroup_from_memcg(struct mem_cgroup *memcg)
+{
+	struct obj_cgroup *objcg;
+
+	if (memcg_kmem_bypass())
+		return NULL;
+
+	rcu_read_lock();
+	objcg = __get_obj_cgroup_from_memcg(memcg);
+	rcu_read_unlock();
+	return objcg;
+}
+
+struct obj_cgroup *get_obj_cgroup_from_cgroup(struct cgroup *cgrp)
+{
+	struct cgroup_subsys_state *css;
+	struct mem_cgroup *memcg;
+	struct obj_cgroup *objcg;
+
+	rcu_read_lock();
+	css = rcu_dereference(cgrp->subsys[memory_cgrp_id]);
+	if (!css || !css_tryget_online(css)) {
+		rcu_read_unlock();
+		cgroup_put(cgrp);
+		return ERR_PTR(-EINVAL);
+	}
+	rcu_read_unlock();
+	cgroup_put(cgrp);
+
+	memcg = mem_cgroup_from_css(css);
+	if (!memcg) {
+		css_put(css);
+		return ERR_PTR(-EINVAL);
+	}
+
+	objcg = get_obj_cgroup_from_memcg(memcg);
+	css_put(css);
+
+	return objcg;
+}
+
 __always_inline struct obj_cgroup *get_obj_cgroup_from_current(void)
 {
 	struct obj_cgroup *objcg = NULL;
-- 
2.17.1