[Ocfs2-devel] ocfs2/dlm: disable BUG_ON when DLM_LOCK_RES_DROPPING_REF, is cleared before dlm_deref_lockres_done_handler

[piaojun <piaojun@huawei.com>]

On 2016-7-11 9:55, Joseph Qi wrote:
> Hi Jun,
> 
> On 2016/7/10 18:01, piaojun wrote:
>> We found a BUG situation in which DLM_LOCK_RES_DROPPING_REF is cleared
>> unexpected that described below. To solve the bug, we disable the BUG_ON
>> and purge lockres in dlm_do_local_recovery_cleanup.
>>
>> Node 1                               Node 2(master)
>> dlm_purge_lockres
>>                                      dlm_deref_lockres_handler
>>
>>                                      DLM_LOCK_RES_SETREF_INPROG is set
>>                                      response DLM_DEREF_RESPONSE_INPROG
>>
>> receive DLM_DEREF_RESPONSE_INPROG
>> stop puring in dlm_purge_lockres
>> and wait for DLM_DEREF_RESPONSE_DONE
>>
>>                                      dispatch dlm_deref_lockres_worker
>>                                      response DLM_DEREF_RESPONSE_DONE
>>
>> receive DLM_DEREF_RESPONSE_DONE and
>> prepare to purge lockres
>>
>>                                      Node 2 goes down
>>
>> find Node2 down and do local
>> clean up for Node2:
>> dlm_do_local_recovery_cleanup
>>   -> clear DLM_LOCK_RES_DROPPING_REF
>>
>> when purging lockres, BUG_ON happens
>> because DLM_LOCK_RES_DROPPING_REF is clear:
>> dlm_deref_lockres_done_handler
>>   ->BUG_ON(!(res->state & DLM_LOCK_RES_DROPPING_REF));
>>
>> Fixes: 60d663cb5273 ("ocfs2/dlm: add DEREF_DONE message")
>> Signed-off-by: Jun Piao <piaojun@huawei.com>
>> ---
>>  fs/ocfs2/dlm/dlmmaster.c | 13 ++++++++++++-
>>  1 file changed, 12 insertions(+), 1 deletion(-)
>>
>> diff --git a/fs/ocfs2/dlm/dlmmaster.c b/fs/ocfs2/dlm/dlmmaster.c
>> index 9aed6e2..f72e7ae 100644
>> --- a/fs/ocfs2/dlm/dlmmaster.c
>> +++ b/fs/ocfs2/dlm/dlmmaster.c
>> @@ -2416,7 +2416,16 @@ int dlm_deref_lockres_done_handler(struct o2net_msg *msg, u32 len, void *data,
>>  	}
>>  
>>  	spin_lock(&res->spinlock);
>> -	BUG_ON(!(res->state & DLM_LOCK_RES_DROPPING_REF));
>> +	if (!(res->state & DLM_LOCK_RES_DROPPING_REF)) {
>> +		spin_unlock(&res->spinlock);
>> +		spin_unlock(&dlm->spinlock);
>> +		mlog(ML_NOTICE, "%s:%.*s: node %u sends deref done "
>> +			"but it is already derefed!\n", dlm->name,
>> +			res->lockname.len, res->lockname.name, node);
>> +		dlm_lockres_put(res);
> So we treat this case as normal?
> If so, we'd better return 0 other than -EINVAL.
> 
> Thanks,
> Joseph
> 
Good suggestion, I will fix this problem in the following [PATCH v2].
Thanks,
Jun Piao
>> +		goto done;
>> +	}
>> +
>>  	if (!list_empty(&res->purge)) {
>>  		mlog(0, "%s: Removing res %.*s from purgelist\n",
>>  			dlm->name, res->lockname.len, res->lockname.name);
>> @@ -2455,6 +2464,8 @@ int dlm_deref_lockres_done_handler(struct o2net_msg *msg, u32 len, void *data,
>>  
>>  	spin_unlock(&dlm->spinlock);
>>  
>> +	ret = 0;
>> +
>>  done:
>>  	dlm_put(dlm);
>>  	return ret;
>>
> 
> 
> 
> .
>