[Ocfs2-devel] [PATCH] ocfs2/dlm: don't handle migrate lockres if already in shutdown

[piaojun <piaojun@huawei.com>]

Hi Changwei,

On 2018/3/2 13:53, Changwei Ge wrote:
> On 2018/3/2 10:09, piaojun wrote:
>> Hi Changwei,
>>
>> On 2018/3/2 9:49, Changwei Ge wrote:
>>> Hi Jun,
>>> I still have some doubts about your problematic situation description .
>>> Please check my reply inline your sequence diagram.
>>>
>>> On 2018/3/1 20:38, piaojun wrote:
>>>> Hi Changwei,
>>>>
>>>> Thanks for your quick reply, please see my comments below.
>>>>
>>>> On 2018/3/1 17:39, Changwei Ge wrote:
>>>>> Hi Jun,
>>>>>
>>>>> On 2018/3/1 17:27, piaojun wrote:
>>>>>> We should not handle migrate lockres if we are already in
>>>>>> 'DLM_CTXT_IN_SHUTDOWN', as that will cause lockres remains after
>>>>>> leaving dlm domain. At last other nodes will get stuck into infinite
>>>>>> loop when requsting lock from us.
>>>>>>
>>>>>>        N1                             N2 (owner)
>>>>>>                                       touch file
>>>>>>
>>>>>> access the file,
>>>>>> and get pr lock
>>>>>>
>>>>>> umount
>>>>>>
>>>>>
>>>>> Before migrating all lock resources, N1 should have already sent
>>>>> DLM_BEGIN_EXIT_DOMAIN_MSG in dlm_begin_exit_domain().
>>>>> N2 will set ->exit_domain_map later.
>>>>> So N2 can't take N1 as migration target.
>>>> Before receiveing N1's DLM_BEGIN_EXIT_DOMAIN_MSG, N2 has picked up N1 as
>>>> the migrate target. So N2 will continue sending lockres to N1 even though
>>>> N1 has left domain. Sorry for making you misunderstanding, I will give a
>>>> more detailed description.
>>>>
>>>>       N1                             N2 (owner)
>>>>                                      touch file
>>>>
>>>> access the file,
>>>> and get pr lock
>>>>
>>>>                                      begin leave domain and
>>>>                                      pick up N1 as new owner
>>>>
>>>> begin leave domain and
>>> Here will clear N1 from N2's dlm->domain_map
>>>
>>>> migrate all lockres do >
>>>>                                      begin migrate lockres to N1
>>> As N1 has been cleared, migrating for this lock resource can't continue.
>> N2 has picked up N1 as new owner in dlm_pick_migration_target() before
>> setting N1 in N2's dlm->exit_domain_map, so N2 will continue migrating
>> lock resource.
> 
> Do you mean that DLM_BEGIN_EXIT_DOMAIN_MSG arrives just before 
> dlm_send_one_lockres() in dlm_migrate_lockres() and after 
> dlm_mark_lockres_migrating()?
Yes, I meant that.

> If so there is race that your problem can happen.
> 
> Well let's move to your code.
> 
>>>
>>> Besides,
>>> I wonder what kind of problem you encountered?
>>> A bug crash? A hang situation?
>>> It's better to share some issue appearance.So perhaps I can help to analyze.:)
>> I encountered a stuck case which described in my changelog.
>>
>> "
>> At last other nodes will get stuck into infinite loop when requsting lock
>> from us.
>> "
>>
>> thanks,
>> Jun
>>>
>>> Thanks,
>>> Changwei
>>>
>>>>
>>>> end leave domain, but
>>>> the lockres left
>>>> unexpectedly, because
>>>> migrate task has passed
>>>>
>>>> thanks,
>>>> Jun
>>>>>
>>>>> How can the scenario your changelog describing happen?
>>>>> Or if miss something?
>>>>>
>>>>> Thanks,
>>>>> Changwei
>>>>>
>>>>>> migrate all lockres
>>>>>>
>>>>>>                                       umount and migrate lockres to N1
>>>>>>
>>>>>> leave dlm domain, but
>>>>>> the lockres left
>>>>>> unexpectedly, because
>>>>>> migrate task has passed
>>>>>>
>>>>>> Signed-off-by: Jun Piao <piaojun@huawei.com>
>>>>>> Reviewed-by: Yiwen Jiang <jiangyiwen@huawei.com>
>>>>>> ---
>>>>>>     fs/ocfs2/dlm/dlmdomain.c   | 14 ++++++++++++++
>>>>>>     fs/ocfs2/dlm/dlmdomain.h   |  1 +
>>>>>>     fs/ocfs2/dlm/dlmrecovery.c |  9 +++++++++
>>>>>>     3 files changed, 24 insertions(+)
>>>>>>
>>>>>> diff --git a/fs/ocfs2/dlm/dlmdomain.c b/fs/ocfs2/dlm/dlmdomain.c
>>>>>> index e1fea14..3b7ec51 100644
>>>>>> --- a/fs/ocfs2/dlm/dlmdomain.c
>>>>>> +++ b/fs/ocfs2/dlm/dlmdomain.c
>>>>>> @@ -675,6 +675,20 @@ static void dlm_leave_domain(struct dlm_ctxt *dlm)
>>>>>>     	spin_unlock(&dlm->spinlock);
>>>>>>     }
>>>>>>
>>>>>> +int dlm_joined(struct dlm_ctxt *dlm)
>>>>>> +{
>>>>>> +	int ret = 0;
>>>>>> +
>>>>>> +	spin_lock(&dlm_domain_lock);
>>>>>> +
>>>>>> +	if (dlm->dlm_state == DLM_CTXT_JOINED)
>>>>>> +		ret = 1;
>>>>>> +
>>>>>> +	spin_unlock(&dlm_domain_lock);
>>>>>> +
>>>>>> +	return ret;
>>>>>> +}
>>>>>> +
> How about use directly use existed function dlm_shutting_down()
I'm afraid that we can't use dlm_shutting_down() directly, as
dlm->dlm_state will be set DLM_CTXT_LEAVING in dlm_mark_domain_leaving()
after N1 migrate all lockres.

> 
>>>>>>     int dlm_shutting_down(struct dlm_ctxt *dlm)
>>>>>>     {
>>>>>>     	int ret = 0;
>>>>>> diff --git a/fs/ocfs2/dlm/dlmdomain.h b/fs/ocfs2/dlm/dlmdomain.h
>>>>>> index fd6122a..2f7f60b 100644
>>>>>> --- a/fs/ocfs2/dlm/dlmdomain.h
>>>>>> +++ b/fs/ocfs2/dlm/dlmdomain.h
>>>>>> @@ -28,6 +28,7 @@
>>>>>>     extern spinlock_t dlm_domain_lock;
>>>>>>     extern struct list_head dlm_domains;
>>>>>>
>>>>>> +int dlm_joined(struct dlm_ctxt *dlm);
>>>>>>     int dlm_shutting_down(struct dlm_ctxt *dlm);
>>>>>>     void dlm_fire_domain_eviction_callbacks(struct dlm_ctxt *dlm,
>>>>>>     					int node_num);
>>>>>> diff --git a/fs/ocfs2/dlm/dlmrecovery.c b/fs/ocfs2/dlm/dlmrecovery.c
>>>>>> index ec8f758..9b3bc66 100644
>>>>>> --- a/fs/ocfs2/dlm/dlmrecovery.c
>>>>>> +++ b/fs/ocfs2/dlm/dlmrecovery.c
>>>>>> @@ -1378,6 +1378,15 @@ int dlm_mig_lockres_handler(struct o2net_msg *msg, u32 len, void *data,
>>>>>>     	if (!dlm_grab(dlm))
>>>>>>     		return -EINVAL;
>>>>>>
>>>>>> +	if (!dlm_joined(dlm)) {
> Here can be if (dlm_shutting_down(dlm)) ?
>>>>>> +		mlog(ML_ERROR, "Domain %s not joined! "
> The log is not accurate. Domain is shutting down will be better, I suppose.
Actually domain is in DLM_CTXT_IN_SHUTDOWN or DLM_CTXT_LEAVING, so we can hardly distinguish here.
So we can only judge domain is not in DLM_CTXT_JOINED.
> 
>>>>>> +				"lockres %.*s, master %u\n",
>>>>>> +				dlm->name, mres->lockname_len,
> I don't like the alignment style.
> How about?
> mlog(ML_ERROR, "Domain %s not joined! "
>       "lockres %.*s, master %u\n",
OK, I will fix this.

thanks,
Jun
> 
> 
> Thanks,
> Changwei
> 
>>>>>> +				mres->lockname, mres->master);
>>>>>> +		dlm_put(dlm);
>>>>>> +		return -EINVAL;
>>>>>> +	}
>>>>>> +
>>>>>>     	BUG_ON(!(mres->flags & (DLM_MRES_RECOVERY|DLM_MRES_MIGRATION)));
>>>>>>
>>>>>>     	real_master = mres->master;
>>>>>>
>>>>> .
>>>>>
>>>>
>>> .
>>>
>>
> .
>