The patch titled
Subject: mm: memcontrol: fix forget to obtain the ref to objcg in split_page_memcg
has been added to the -mm tree. Its filename is
mm-memcontrol-fix-forget-to-obtain-the-ref-to-objcg-in-split_page_memcg.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/mm-memcontrol-fix-forget-to-obtain-the-ref-to-objcg-in-split_page_memcg.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/mm-memcontrol-fix-forget-to-obtain-the-ref-to-objcg-in-split_page_memcg.patch
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------------------------------------------------------
From: Muchun Song <songmuchun@xxxxxxxxxxxxx>
Subject: mm: memcontrol: fix forget to obtain the ref to objcg in split_page_memcg
Christian Borntraeger reported a warning about "percpu ref
(obj_cgroup_release) <= 0 (-1) after switching to atomic". Because we
forgot to obtain the reference to the objcg and wrongly obtain the
reference of memcg.
Link: https://lkml.kernel.org/r/20210401030141.37061-1-songmuchun@xxxxxxxxxxxxx
Signed-off-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
Reported-by: Christian Borntraeger <borntraeger@xxxxxxxxxx>
Acked-by: Roman Gushchin <guro@xxxxxx>
Cc: Miaohe Lin <linmiaohe@xxxxxxxxxx>
Cc: Xiongchun Duan <duanxiongchun@xxxxxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxxxx>
Cc: Shakeel Butt <shakeelb@xxxxxxxxxx>
Cc: Vladimir Davydov <vdavydov.dev@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/memcontrol.h | 6 ++++++
mm/memcontrol.c | 6 +++++-
2 files changed, 11 insertions(+), 1 deletion(-)
--- a/include/linux/memcontrol.h~mm-memcontrol-fix-forget-to-obtain-the-ref-to-objcg-in-split_page_memcg
+++ a/include/linux/memcontrol.h
@@ -803,6 +803,12 @@ static inline void obj_cgroup_get(struct
percpu_ref_get(&objcg->refcnt);
}
+static inline void obj_cgroup_get_many(struct obj_cgroup *objcg,
+ unsigned long nr)
+{
+ percpu_ref_get_many(&objcg->refcnt, nr);
+}
+
static inline void obj_cgroup_put(struct obj_cgroup *objcg)
{
percpu_ref_put(&objcg->refcnt);
--- a/mm/memcontrol.c~mm-memcontrol-fix-forget-to-obtain-the-ref-to-objcg-in-split_page_memcg
+++ a/mm/memcontrol.c
@@ -3257,7 +3257,11 @@ void split_page_memcg(struct page *head,
for (i = 1; i < nr; i++)
head[i].memcg_data = head->memcg_data;
- css_get_many(&memcg->css, nr - 1);
+
+ if (PageMemcgKmem(head))
+ obj_cgroup_get_many(__page_objcg(head), nr - 1);
+ else
+ css_get_many(&memcg->css, nr - 1);
}
#ifdef CONFIG_MEMCG_SWAP
_
Patches currently in -mm which might be from songmuchun@xxxxxxxxxxxxx are
mm-memcontrol-fix-kernel-stack-account.patch
mm-memcontrol-slab-fix-obtain-a-reference-to-a-freeing-memcg.patch
mm-memcontrol-introduce-obj_cgroup_uncharge_pages.patch
mm-memcontrol-directly-access-page-memcg_data-in-mm-page_allocc.patch
mm-memcontrol-change-ug-dummy_page-only-if-memcg-changed.patch
mm-memcontrol-use-obj_cgroup-apis-to-charge-kmem-pages.patch
mm-memcontrol-inline-__memcg_kmem_uncharge-into-obj_cgroup_uncharge_pages.patch
mm-memcontrol-move-pagememcgkmem-to-the-scope-of-config_memcg_kmem.patch
mm-memcontrol-fix-forget-to-obtain-the-ref-to-objcg-in-split_page_memcg.patch
