From: Greg Kroah-Hartman <gre...@linuxfoundation.org>
From: Zhou Guanghui <zhouguangh...@huawei.com>
commit e1baddf8475b06cc56f4bafecf9a32a124343d9f upstream.
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-zhouguangh...@huawei.com
Signed-off-by: Zhou Guanghui <zhouguangh...@huawei.com>
Acked-by: Johannes Weiner <han...@cmpxchg.org>
Reviewed-by: Zi Yan <z...@nvidia.com>
Reviewed-by: Shakeel Butt <shake...@google.com>
Acked-by: Michal Hocko <mho...@suse.com>
Cc: Hanjun Guo <guohan...@huawei.com>
Cc: Hugh Dickins <hu...@google.com>
Cc: Kefeng Wang <wangkefeng.w...@huawei.com>
Cc: "Kirill A. Shutemov" <kirill.shute...@linux.intel.com>
Cc: Nicholas Piggin <npig...@gmail.com>
Cc: Rui Xiang <rui.xi...@huawei.com>
Cc: Tianhong Ding <dingtianh...@huawei.com>
Cc: Weilong Chen <chenweil...@huawei.com>
Cc: <sta...@vger.kernel.org>
Signed-off-by: Andrew Morton <a...@linux-foundation.org>
Signed-off-by: Linus Torvalds <torva...@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
mm/page_alloc.c | 1 +
1 file changed, 1 insertion(+)
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3313,6 +3313,7 @@ void split_page(struct page *page, unsig
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);
