mm/vmscan: dont reclaim anon page when shrink page cache

hulk inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I4SK3S


CVE: NA

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The number of page cache should be limited in a range if
enable CONFIG_MEMORY_RELIABLE, so only page cache instead
of both file + anono page should be reclaimed during page
cache reclaimtion.

Signed-off-by: Chen Wandun <chenwandun@huawei.com>
Reviewed-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>