!2716 ext4: recheck buffer valid after page unlock

Merge Pull Request from: @ci-robot 
 
PR sync from: yangerkun <yangerkun@huawei.com>
https://mailweb.openeuler.org/hyperkitty/list/kernel@openeuler.org/message/KM5ZGQQVCMZJORVBS7ZBCITFCOIN7S7L/ 
 
https://gitee.com/openeuler/kernel/issues/I8BBWH 
 
Link:https://gitee.com/openeuler/kernel/pulls/2716

 

Reviewed-by: zhangyi (F) <yi.zhang@huawei.com>
Signed-off-by: Jialin Zhang <zhangjialin11@huawei.com>