!6397 btrfs: fix data race at btrfs_use_block_rsv() when accessing block reserve

Merge Pull Request from: @ci-robot 
 
PR sync from: Zizhi Wo <wozizhi@huawei.com>
https://mailweb.openeuler.org/hyperkitty/list/kernel@openeuler.org/message/OPXCWIZKFLHLWLNCONIBNIKL225P44ZM/ 
 
https://gitee.com/src-openeuler/kernel/issues/I9HK4U 
 
Link:https://gitee.com/openeuler/kernel/pulls/6397

 

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