[RFC PATCH bpf-next 03/10] mm, memcg: Add new helper obj_cgroup_from_current()

Yafang Shao
2022-06-19T15:50:52Z

The difference between get_obj_cgroup_from_current() and obj_cgroup_from_current()
is that the later one doesn't add objcg's refcnt.

Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
---
include/linux/memcontrol.h | 1 +
mm/memcontrol.c | 24 ++++++++++++++++++++++++
2 files changed, 25 insertions(+)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index cf074156c6ac..402b42670bcd 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -1703,6 +1703,7 @@ 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 *obj_cgroup_from_current(void);
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 abec50f31fe6..350a7849dac3 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2950,6 +2950,30 @@ struct obj_cgroup *get_obj_cgroup_from_page(struct page *page)
return objcg;
}

+__always_inline struct obj_cgroup *obj_cgroup_from_current(void)
+{
+ struct obj_cgroup *objcg = NULL;
+ struct mem_cgroup *memcg;
+
+ if (memcg_kmem_bypass())
+ return NULL;
+
+ rcu_read_lock();
+ if (unlikely(active_memcg()))
+ memcg = active_memcg();
+ else
+ memcg = mem_cgroup_from_task(current);
+
+ for (; memcg != root_mem_cgroup; memcg = parent_mem_cgroup(memcg)) {
+ objcg = rcu_dereference(memcg->objcg);
+ if (objcg)
+ break;
+ }
+ rcu_read_unlock();
+
+ return objcg;
+}
+
static void memcg_account_kmem(struct mem_cgroup *memcg, int nr_pages)
{
mod_memcg_state(memcg, MEMCG_KMEM, nr_pages);
--
2.17.1