The patch below does not apply to the 5.10-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@xxxxxxxxxxxxxxx>.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
>From e1baddf8475b06cc56f4bafecf9a32a124343d9f Mon Sep 17 00:00:00 2001
From: Zhou Guanghui <zhouguanghui1@xxxxxxxxxx>
Date: Fri, 12 Mar 2021 21:08:33 -0800
Subject: [PATCH] mm/memcg: set memcg when splitting page
As described in the split_page() comment, for the non-compound high order
page, the sub-pages must be freed individually. If the memcg of the first
page is valid, the tail pages cannot be uncharged when be freed.
For example, when alloc_pages_exact is used to allocate 1MB continuous
physical memory, 2MB is charged(kmemcg is enabled and __GFP_ACCOUNT is
set). When make_alloc_exact free the unused 1MB and free_pages_exact free
the applied 1MB, actually, only 4KB(one page) is uncharged.
Therefore, the memcg of the tail page needs to be set when splitting a
page.
Michel:
There are at least two explicit users of __GFP_ACCOUNT with
alloc_exact_pages added recently. See 7efe8ef274024 ("KVM: arm64:
Allocate stage-2 pgd pages with GFP_KERNEL_ACCOUNT") and c419621873713
("KVM: s390: Add memcg accounting to KVM allocations"), so this is not
just a theoretical issue.
Link: https://lkml.kernel.org/r/20210304074053.65527-3-zhouguanghui1@xxxxxxxxxx
Signed-off-by: Zhou Guanghui <zhouguanghui1@xxxxxxxxxx>
Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>
Reviewed-by: Zi Yan <ziy@xxxxxxxxxx>
Reviewed-by: Shakeel Butt <shakeelb@xxxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Cc: Hanjun Guo <guohanjun@xxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx>
Cc: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Nicholas Piggin <npiggin@xxxxxxxxx>
Cc: Rui Xiang <rui.xiang@xxxxxxxxxx>
Cc: Tianhong Ding <dingtianhong@xxxxxxxxxx>
Cc: Weilong Chen <chenweilong@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 3cd1c0ce4d06..cfc72873961d 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3314,6 +3314,7 @@ void split_page(struct page *page, unsigned int order)
for (i = 1; i < (1 << order); i++)
set_page_refcounted(page + i);
split_page_owner(page, 1 << order);
+ split_page_memcg(page, 1 << order);
}
EXPORT_SYMBOL_GPL(split_page);
