diff options
author | Muchun Song <songmuchun@bytedance.com> | 2021-06-28 19:38:03 -0700 |
---|---|---|
committer | Linus Torvalds <torvalds@linux-foundation.org> | 2021-06-29 10:53:50 -0700 |
commit | 9838354e16a2a920d5a228559850d10fa588a18d (patch) | |
tree | b8c00b505726ab6a9cba21d454d42dfcbad09559 | |
parent | 7467c39128bda1d58af08aaeb0c7ba54d0ec87ae (diff) |
mm: memcontrol: simplify the logic of objcg pinning memcg
The obj_cgroup_release() and memcg_reparent_objcgs() are serialized by the
css_set_lock. We do not need to care about objcg->memcg being released in
the process of obj_cgroup_release(). So there is no need to pin memcg
before releasing objcg. Remove those pinning logic to simplfy the code.
There are only two places that modifies the objcg->memcg. One is the
initialization to objcg->memcg in the memcg_online_kmem(), another is
objcgs reparenting in the memcg_reparent_objcgs(). It is also impossible
for the two to run in parallel. So xchg() is unnecessary and it is enough
to use WRITE_ONCE().
Link: https://lkml.kernel.org/r/20210417043538.9793-7-songmuchun@bytedance.com
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Acked-by: Roman Gushchin <guro@fb.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Xiongchun Duan <duanxiongchun@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r-- | mm/memcontrol.c | 20 |
1 files changed, 6 insertions, 14 deletions
diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 946a9a483e71..c79b6926fe83 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -261,7 +261,6 @@ static void obj_cgroup_uncharge_pages(struct obj_cgroup *objcg, static void obj_cgroup_release(struct percpu_ref *ref) { struct obj_cgroup *objcg = container_of(ref, struct obj_cgroup, refcnt); - struct mem_cgroup *memcg; unsigned int nr_bytes; unsigned int nr_pages; unsigned long flags; @@ -291,11 +290,9 @@ static void obj_cgroup_release(struct percpu_ref *ref) nr_pages = nr_bytes >> PAGE_SHIFT; spin_lock_irqsave(&css_set_lock, flags); - memcg = obj_cgroup_memcg(objcg); if (nr_pages) obj_cgroup_uncharge_pages(objcg, nr_pages); list_del(&objcg->list); - mem_cgroup_put(memcg); spin_unlock_irqrestore(&css_set_lock, flags); percpu_ref_exit(ref); @@ -330,17 +327,12 @@ static void memcg_reparent_objcgs(struct mem_cgroup *memcg, spin_lock_irq(&css_set_lock); - /* Move active objcg to the parent's list */ - xchg(&objcg->memcg, parent); - css_get(&parent->css); - list_add(&objcg->list, &parent->objcg_list); - - /* Move already reparented objcgs to the parent's list */ - list_for_each_entry(iter, &memcg->objcg_list, list) { - css_get(&parent->css); - xchg(&iter->memcg, parent); - css_put(&memcg->css); - } + /* 1) Ready to reparent active objcg. */ + list_add(&objcg->list, &memcg->objcg_list); + /* 2) Reparent active objcg and already reparented objcgs to parent. */ + list_for_each_entry(iter, &memcg->objcg_list, list) + WRITE_ONCE(iter->memcg, parent); + /* 3) Move already reparented objcgs to the parent's list */ list_splice(&memcg->objcg_list, &parent->objcg_list); spin_unlock_irq(&css_set_lock); |