!9858 khugepaged: fix null-pointer dereference due to race

Merge Pull Request from: @ci-robot 
 
PR sync from: Liu Shixin <liushixin2@huawei.com>
https://mailweb.openeuler.org/hyperkitty/list/kernel@openeuler.org/message/546YAS7FT4HYQRMH2PPSSEX3DC3AQAIM/ 
 
https://gitee.com/openeuler/kernel/issues/IABZNI 
 
Link:https://gitee.com/openeuler/kernel/pulls/9858

 

Reviewed-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Reviewed-by: Liu YongQiang <liuyongqiang13@huawei.com>
Signed-off-by: Zhang Changzhong <zhangchangzhong@huawei.com>