[Ocfs2-devel] [PATCH] ocfs2/dlm: wait for dlm recovery done when migrating all lockres

[piaojun <piaojun@huawei.com>]

Hi Changwei,

On 2017/11/1 10:47, Changwei Ge wrote:
> Hi Jun,
> 
> Thanks for reporting.
> I am very interesting in this issue. But, first of all, I want to make 
> this issue clear, so that I might be able to provide some comments.
> 
> 
> On 2017/11/1 9:16, piaojun wrote:
>> wait for dlm recovery done when migrating all lockres in case of new
>> lockres to be left after leaving dlm domain.
> 
> What do you mean by 'a new lock resource to be left after leaving 
> domain'? It means we leak a dlm lock resource if below situation happens.
> 
a new lockres is the one collected by NodeA during recoverying for
NodeB. It leaks a lockres indeed.
>>
>>        NodeA                       NodeB                NodeC
>>
>> umount and migrate
>> all lockres
>>
>>                                   node down
>>
>> do recovery for NodeB
>> and collect a new lockres
>> form other live nodes
> 
> You mean a lock resource whose owner was NodeB is just migrated from 
> other cluster member nodes?
> 
that is it.
>>
>> leave domain but the
>> new lockres remains
>>
>>                                                    mount and join domain
>>
>>                                                    request for the owner
>>                                                    of the new lockres, but
>>                                                    all the other nodes said
>>                                                    'NO', so NodeC decide to
>>                                                    the owner, and send do
>>                                                    assert msg to other nodes.
>>
>>                                                    other nodes receive the msg
>>                                                    and found two masters exist.
>>                                                    at last cause BUG in
>>                                                    dlm_assert_master_handler()
>>                                                    -->BUG();
> 
> If this issue truly exists, can we take some efforts in 
> dlm_exit_domain_handler? Or perhaps we should kick dlm's work queue 
> before migrating all lock resources.
> 
If NodeA has entered dlm_leave_domain(), we can hardly go back
migrating res. Perhaps more work will be needed in that way.
>>
>> Fixes: bc9838c4d44a ("dlm: allow dlm do recovery during shutdown")
>>
>> Signed-off-by: Jun Piao <piaojun@huawei.com>
>> Reviewed-by: Alex Chen <alex.chen@huawei.com>
>> Reviewed-by: Yiwen Jiang <jiangyiwen@huawei.com>
>> ---
>>   fs/ocfs2/dlm/dlmcommon.h   |  1 +
>>   fs/ocfs2/dlm/dlmdomain.c   | 14 ++++++++++++++
>>   fs/ocfs2/dlm/dlmrecovery.c | 12 +++++++++---
>>   3 files changed, 24 insertions(+), 3 deletions(-)
>>
>> diff --git a/fs/ocfs2/dlm/dlmcommon.h b/fs/ocfs2/dlm/dlmcommon.h
>> index e9f3705..999ab7d 100644
>> --- a/fs/ocfs2/dlm/dlmcommon.h
>> +++ b/fs/ocfs2/dlm/dlmcommon.h
>> @@ -140,6 +140,7 @@ struct dlm_ctxt
>>   	u8 node_num;
>>   	u32 key;
>>   	u8  joining_node;
>> +	u8 migrate_done; /* set to 1 means node has migrated all lockres */
>>   	wait_queue_head_t dlm_join_events;
>>   	unsigned long live_nodes_map[BITS_TO_LONGS(O2NM_MAX_NODES)];
>>   	unsigned long domain_map[BITS_TO_LONGS(O2NM_MAX_NODES)];
>> diff --git a/fs/ocfs2/dlm/dlmdomain.c b/fs/ocfs2/dlm/dlmdomain.c
>> index e1fea14..98a8f56 100644
>> --- a/fs/ocfs2/dlm/dlmdomain.c
>> +++ b/fs/ocfs2/dlm/dlmdomain.c
>> @@ -461,6 +461,18 @@ static int dlm_migrate_all_locks(struct dlm_ctxt *dlm)
>>   		cond_resched_lock(&dlm->spinlock);
>>   		num += n;
>>   	}
>> +
>> +	if (!num) {
>> +		if (dlm->reco.state & DLM_RECO_STATE_ACTIVE) {
>> +			mlog(0, "%s: perhaps there are more lock resources need to "
>> +					"be migrated after dlm recovery\n", dlm->name);
> 
> If dlm is mark with DLM_RECO_STATE_ACTIVE, then a lock resource must 
> already be marked with DLM_LOCK_RES_RECOVERING which can't be migrated. 
> So code will goto redo_bucket in function dlm_migrate_all_locks.
> So I don't understand why a judgement is added here?
> 
> 
> 
because we have done migrating before recoverying. the judgement here
is to avoid the following potential recoverying.
>> +			ret = -EAGAIN;
>> +		} else {
>> +			mlog(0, "%s: we won't do dlm recovery after migrating all lockres",
>> +					dlm->name);
>> +			dlm->migrate_done = 1;
>> +		}
>> +	}
>>   	spin_unlock(&dlm->spinlock);
>>   	wake_up(&dlm->dlm_thread_wq);
>>
>> @@ -2052,6 +2064,8 @@ static struct dlm_ctxt *dlm_alloc_ctxt(const char *domain,
>>   	dlm->joining_node = DLM_LOCK_RES_OWNER_UNKNOWN;
>>   	init_waitqueue_head(&dlm->dlm_join_events);
>>
>> +	dlm->migrate_done = 0;
>> +
>>   	dlm->reco.new_master = O2NM_INVALID_NODE_NUM;
>>   	dlm->reco.dead_node = O2NM_INVALID_NODE_NUM;
>>
>> diff --git a/fs/ocfs2/dlm/dlmrecovery.c b/fs/ocfs2/dlm/dlmrecovery.c
>> index 74407c6..3106332 100644
>> --- a/fs/ocfs2/dlm/dlmrecovery.c
>> +++ b/fs/ocfs2/dlm/dlmrecovery.c
>> @@ -423,12 +423,11 @@ void dlm_wait_for_recovery(struct dlm_ctxt *dlm)
>>
>>   static void dlm_begin_recovery(struct dlm_ctxt *dlm)
>>   {
>> -	spin_lock(&dlm->spinlock);
>> +	assert_spin_locked(&dlm->spinlock);
>>   	BUG_ON(dlm->reco.state & DLM_RECO_STATE_ACTIVE);
>>   	printk(KERN_NOTICE "o2dlm: Begin recovery on domain %s for node %u\n",
>>   	       dlm->name, dlm->reco.dead_node);
>>   	dlm->reco.state |= DLM_RECO_STATE_ACTIVE;
>> -	spin_unlock(&dlm->spinlock);
>>   }
>>
>>   static void dlm_end_recovery(struct dlm_ctxt *dlm)
>> @@ -456,6 +455,12 @@ static int dlm_do_recovery(struct dlm_ctxt *dlm)
>>
>>   	spin_lock(&dlm->spinlock);
>>
>> +	if (dlm->migrate_done) {
>> +		mlog(0, "%s: no need do recovery after migrating all lockres\n",
>> +				dlm->name);
> 
> Don't we need unlock above spin_lock before return?
> 
> And if we just return here, how dlm lock resource can clear its 
> REDISCOVERING flag. I suppose this may cause cluster hang.
> 
> And I cc this to ocfs2 maintainers.
> 
> Thanks,
> Changwei
> 
oh, good catch, I missed spin_unlock(&dlm->spinlock);
>> +		return 0;
>> +	}
>> +
>>   	/* check to see if the new master has died */
>>   	if (dlm->reco.new_master != O2NM_INVALID_NODE_NUM &&
>>   	    test_bit(dlm->reco.new_master, dlm->recovery_map)) {
>> @@ -490,12 +495,13 @@ static int dlm_do_recovery(struct dlm_ctxt *dlm)
>>   	mlog(0, "%s(%d):recovery thread found node %u in the recovery map!\n",
>>   	     dlm->name, task_pid_nr(dlm->dlm_reco_thread_task),
>>   	     dlm->reco.dead_node);
>> -	spin_unlock(&dlm->spinlock);
>>
>>   	/* take write barrier */
>>   	/* (stops the list reshuffling thread, proxy ast handling) */
>>   	dlm_begin_recovery(dlm);
>>
>> +	spin_unlock(&dlm->spinlock);
>> +
>>   	if (dlm->reco.new_master == dlm->node_num)
>>   		goto master_here;
>>
> 
> .
>