mm: memcontrol: consolidate lruvec stat flushing

mainline inclusion
from mainline-v5.13-rc1
commit 2cd21c89
category: feature
bugzilla: 185803 https://gitee.com/openeuler/kernel/issues/I4JOG9?from=project-issue
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=2cd21c89800c

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There are two functions to flush the per-cpu data of an lruvec into the
rest of the cgroup tree: when the cgroup is being freed, and when a CPU
disappears during hotplug.  The difference is whether all CPUs or just
one is being collected, but the rest of the flushing code is the same.
Merge them into one function and share the common code.

Link: https://lkml.kernel.org/r/20210209163304.77088-8-hannes@cmpxchg.org


Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Roman Gushchin <guro@fb.com>
Cc: Michal Koutný <mkoutny@suse.com>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Lu Jialin <lujialin4@huawei.com>
Reviewed-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>