!7682 dm snapshot: fix lockup in dm_exception_table_exit

Merge Pull Request from: @ci-robot 
 
PR sync from: Li Lingfeng <lilingfeng3@huawei.com>
https://mailweb.openeuler.org/hyperkitty/list/kernel@openeuler.org/message/NJLX4DPRGSKCJ3LIV2P7E4DT355KAWTF/ 
 
https://gitee.com/src-openeuler/kernel/issues/I9Q9CC 
 
Link:https://gitee.com/openeuler/kernel/pulls/7682

 

Reviewed-by: Liu YongQiang <liuyongqiang13@huawei.com>
Reviewed-by: Yu Kuai <yukuai3@huawei.com>
Signed-off-by: Zhang Changzhong <zhangchangzhong@huawei.com>