mm: clear_freelist_page: Provide timeout mechanism for worker runtime

hulk inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I558LD


CVE: NA

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In the case of large memory, the clear freelist will hold zone lock
for a long time. As a result, the process may be blocked unless clear
freelist thread exit, and causing the system to be reset by the watchdog.

Provide a mechanism to stop clear freelist threads when elapsed time
exceeds cfp_timeout, which can be set by module_param().

Signed-off-by: Yu Liao <liaoyu15@huawei.com>
Reviewed-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Signed-off-by: Yongqiang Liu <liuyongqiang13@huawei.com>