mm: memcontrol/slab: Use helpers to access slab page's memcg_data

mainline inclusion
from mainline-v5.11-rc1
commit 270c6a71
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I4C0GB
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=270c6a71460e12b07b1dcadf7457ff95b6c6e8f4



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To gather all direct accesses to struct page's memcg_data field in one
place, let's introduce 3 new helpers to use in the slab accounting code:

  struct obj_cgroup **page_objcgs(struct page *page);
  struct obj_cgroup **page_objcgs_check(struct page *page);
  bool set_page_objcgs(struct page *page, struct obj_cgroup **objcgs);

They are similar to the corresponding API for generic pages, except that
the setter can return false, indicating that the value has been already
set from a different thread.

Signed-off-by: Roman Gushchin <guro@fb.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Link: https://lkml.kernel.org/r/20201027001657.3398190-3-guro@fb.com
Link: https://lore.kernel.org/bpf/20201201215900.3569844-3-guro@fb.com


Signed-off-by: Chen Huang <chenhuang5@huawei.com>
Reviewed-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Reviewed-by: Chen Wandun <chenwandun@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>