mm: Add sysctl to clear free list pages

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


CVE: NA

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This patch add sysctl to clear pages in free lists of each NUMA node.
For each NUMA node, clear each page in the free list, these work is
scheduled on a random CPU of the NUMA node.

When kasan is enabled and the pages are free, the shadow memory will be
filled with 0xFF, writing these free pages will cause UAF, so just
disable KASAN for clear freelist.

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>