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

[Changwei Ge]

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.

> 
>        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?

> 
> 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.

> 
> Fixes: bc9838c4d44a ("dlm: allow dlm do recovery during shutdown")
> 
> Signed-off-by: Jun Piao <piaojun at huawei.com>
> Reviewed-by: Alex Chen <alex.chen at huawei.com>
> Reviewed-by: Yiwen Jiang <jiangyiwen at 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?



> +			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

> +		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;
>