[Ocfs2-devel] [PATCH] ocfs2/dlm: ignore cleaning the migration mle that is inuse

[Junxiao Bi]

Hi Jiufei,

When target node down, mle is cleared from
dlm_do_local_recovery_cleanup()->dlm_clean_master_list()->dlm_clean_migration_mle()?
mle->woken is set to 1 in dlm_clean_migration_mle(), so the code to
detect target node down(if (dlm_is_node_dead(dlm, target))) will never
be run in dlm_migrate_lockres()?


2621         while (1) {
2622                 ret = wait_event_interruptible_timeout(mle->wq,
2623                                         (atomic_read(&mle->woken)
== 1),
2624                                         msecs_to_jiffies(5000));
2625
2626                 if (ret >= 0) {
2627                         if (atomic_read(&mle->woken) == 1 ||
2628                             res->owner == target)
2629                                 break;
2630
2631                         mlog(0, "%s:%.*s: timed out during
migration\n",
2632                              dlm->name, res->lockname.len,
res->lockname.name);
2633                         /* avoid hang during shutdown when
migrating lockres
2634                          * to a node which also goes down */
2635                         if (dlm_is_node_dead(dlm, target)) {
2636                                 mlog(0, "%s:%.*s: expected migration "
2637                                      "target %u is no longer up,
restarting\n",
2638                                      dlm->name, res->lockname.len,
2639                                      res->lockname.name, target);
2640                                 ret = -EINVAL;
2641                                 /* migration failed, detach and
clean up mle */
2642                                 dlm_mle_detach_hb_events(dlm, mle);
2643                                 dlm_put_mle(mle);
2644                                 dlm_put_mle_inuse(mle);
2645                                 spin_lock(&res->spinlock);
2646                                 res->state &= ~DLM_LOCK_RES_MIGRATING;
2647                                 wake = 1;
2648                                 spin_unlock(&res->spinlock);
2649                                 goto leave;
2650                         }
2651                 } else
2652                         mlog(0, "%s:%.*s: caught signal during
migration\n",
2653                              dlm->name, res->lockname.len,
res->lockname.name);
2654         }


Thanks,
Junxiao.
On 12/28/2015 03:44 PM, xuejiufei wrote:
> We have found that migration source will trigger a BUG that the
> refcount of mle is already zero before put when the target is
> down during migration. The situation is as follows:
> 
> dlm_migrate_lockres
>   dlm_add_migration_mle
>   dlm_mark_lockres_migrating
>   dlm_get_mle_inuse
>   <<<<<< Now the refcount of the mle is 2.
>   dlm_send_one_lockres and wait for the target to become the
>   new master.
>   <<<<<< o2hb detect the target down and clean the migration
>   mle. Now the refcount is 1.
> 
> dlm_migrate_lockres woken, and put the mle twice when found
> the target goes down which trigger the BUG with the following
> message:
> "ERROR: bad mle: ".
> 
> Signed-off-by: Jiufei Xue <xuejiufei at huawei.com>
> Reviewed-by: Joseph Qi <joseph.qi at huawei.com>
> ---
>  fs/ocfs2/dlm/dlmmaster.c | 26 +++++++++++++++-----------
>  1 file changed, 15 insertions(+), 11 deletions(-)
> 
> diff --git a/fs/ocfs2/dlm/dlmmaster.c b/fs/ocfs2/dlm/dlmmaster.c
> index 936e11b..b713140 100644
> --- a/fs/ocfs2/dlm/dlmmaster.c
> +++ b/fs/ocfs2/dlm/dlmmaster.c
> @@ -2519,6 +2519,11 @@ static int dlm_migrate_lockres(struct dlm_ctxt *dlm,
>  	spin_lock(&dlm->master_lock);
>  	ret = dlm_add_migration_mle(dlm, res, mle, &oldmle, name,
>  				    namelen, target, dlm->node_num);
> +	/* get an extra reference on the mle.
> +	 * otherwise the assert_master from the new
> +	 * master will destroy this.
> +	 */
> +	dlm_get_mle_inuse(mle);
>  	spin_unlock(&dlm->master_lock);
>  	spin_unlock(&dlm->spinlock);
> 
> @@ -2554,6 +2559,7 @@ fail:
>  		if (mle_added) {
>  			dlm_mle_detach_hb_events(dlm, mle);
>  			dlm_put_mle(mle);
> +			dlm_put_mle_inuse(mle);
>  		} else if (mle) {
>  			kmem_cache_free(dlm_mle_cache, mle);
>  			mle = NULL;
> @@ -2571,17 +2577,6 @@ fail:
>  	 * ensure that all assert_master work is flushed. */
>  	flush_workqueue(dlm->dlm_worker);
> 
> -	/* get an extra reference on the mle.
> -	 * otherwise the assert_master from the new
> -	 * master will destroy this.
> -	 * also, make sure that all callers of dlm_get_mle
> -	 * take both dlm->spinlock and dlm->master_lock */
> -	spin_lock(&dlm->spinlock);
> -	spin_lock(&dlm->master_lock);
> -	dlm_get_mle_inuse(mle);
> -	spin_unlock(&dlm->master_lock);
> -	spin_unlock(&dlm->spinlock);
> -
>  	/* notify new node and send all lock state */
>  	/* call send_one_lockres with migration flag.
>  	 * this serves as notice to the target node that a
> @@ -3312,6 +3307,15 @@ top:
>  			    mle->new_master != dead_node)
>  				continue;
> 
> +			if (mle->new_master == dead_node && mle->inuse) {
> +				mlog(ML_NOTICE, "%s: target %u died during "
> +						"migration from %u, the MLE is "
> +						"still keep used, ignore it!\n",
> +						dlm->name, dead_node,
> +						mle->master);
> +				continue;
> +			}
> +
>  			/* If we have reached this point, this mle needs to be
>  			 * removed from the list and freed. */
>  			dlm_clean_migration_mle(dlm, mle);
>