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From:   Zhou Guanghui <zhouguanghui1@huawei.com>
To:     <linux-kernel@vger.kernel.org>, <linux-mm@kvack.org>
CC:     <akpm@linux-foundation.org>, <npiggin@suse.de>,
        <wangkefeng.wang@huawei.com>, <guohanjun@huawei.com>,
        <dingtianhong@huawei.com>, <chenweilong@huawei.com>,
        <rui.xiang@huawei.com>
Subject: [PATCH] mm/memcg: set memcg when split pages
Date:   Tue, 2 Mar 2021 01:34:51 +0000
Message-ID: <20210302013451.118701-1-zhouguanghui1@huawei.com>
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Precedence: bulk

When split page, the memory cgroup info recorded in first page is
not copied to tail pages. In this case, when the tail pages are
freed, the uncharge operation is not performed. As a result, the
usage of this memcg keeps increasing, and the OOM may occur.

So, the copying of first page's memory cgroup info to tail pages
is needed when split page.

Signed-off-by: Zhou Guanghui <zhouguanghui1@huawei.com>
---
 include/linux/memcontrol.h | 10 ++++++++++
 mm/page_alloc.c            |  4 +++-
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index e6dc793d587d..c7e2b4421dc1 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -867,6 +867,12 @@ void mem_cgroup_print_oom_group(struct mem_cgroup *memcg);
 extern bool cgroup_memory_noswap;
 #endif
 
+static inline void copy_page_memcg(struct page *dst, struct page *src)
+{
+	if (src->memcg_data)
+		dst->memcg_data = src->memcg_data;
+}
+
 struct mem_cgroup *lock_page_memcg(struct page *page);
 void __unlock_page_memcg(struct mem_cgroup *memcg);
 void unlock_page_memcg(struct page *page);
@@ -1291,6 +1297,10 @@ mem_cgroup_print_oom_meminfo(struct mem_cgroup *memcg)
 {
 }
 
+static inline void copy_page_memcg(struct page *dst, struct page *src)
+{
+}
+
 static inline struct mem_cgroup *lock_page_memcg(struct page *page)
 {
 	return NULL;
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 3e4b29ee2b1e..ee0a63dc1c9b 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3307,8 +3307,10 @@ void split_page(struct page *page, unsigned int order)
 	VM_BUG_ON_PAGE(PageCompound(page), page);
 	VM_BUG_ON_PAGE(!page_count(page), page);
 
-	for (i = 1; i < (1 << order); i++)
+	for (i = 1; i < (1 << order); i++) {
 		set_page_refcounted(page + i);
+		copy_page_memcg(page + i, page);
+	}
 	split_page_owner(page, 1 << order);
 }
 EXPORT_SYMBOL_GPL(split_page);
-- 
2.25.0