[Ocfs2-devel] ocfs2/dlm: solve a BUG when deref failed in dlm_drop_lockres_ref

[Joseph Qi]

On 2016/7/10 18:03, piaojun wrote:
> We found a BUG situation that lockres is migrated during deref
> described below. To solve the BUG, we could purge lockres directly when
> other node says I did not have a ref. Additionally, we'd better purge
> lockres if master goes down, as no one will response deref done.
> 
> Node 1                  Node 2(old master)             Node3(new master)
> dlm_purge_lockres
> send deref to N2
> 
>                         leave domain
>                         migrate lockres to N3
>                                                        finish migration
>                                                        send do assert
>                                                        master to N1
> 
> receive do assert msg
> form N3, but can not
> find lockres because
> DROPPING_REF is set,
> so the owner is still
> N2.
> 
>                         receive deref from N1
>                         and response -EINVAL
>                         because lockres is migrated
> 
> BUG when receive -EINVAL
> in dlm_drop_lockres_ref
> 
> Fixes: 842b90b62461d ("ocfs2/dlm: return in progress if master can not clear the refmap bit...")
> Signed-off-by: Jun Piao <piaojun at huawei.com>
Use full patch title please.
Others looks well.

Thanks,
Joseph

> ---
>  fs/ocfs2/dlm/dlmmaster.c |  9 ++++++---
>  fs/ocfs2/dlm/dlmthread.c | 13 +++++++++++--
>  2 files changed, 17 insertions(+), 5 deletions(-)
> 
> diff --git a/fs/ocfs2/dlm/dlmmaster.c b/fs/ocfs2/dlm/dlmmaster.c
> index f72e7ae..8c84641 100644
> --- a/fs/ocfs2/dlm/dlmmaster.c
> +++ b/fs/ocfs2/dlm/dlmmaster.c
> @@ -2276,9 +2276,12 @@ int dlm_drop_lockres_ref(struct dlm_ctxt *dlm, struct dlm_lock_resource *res)
>  		mlog(ML_ERROR, "%s: res %.*s, DEREF to node %u got %d\n",
>  		     dlm->name, namelen, lockname, res->owner, r);
>  		dlm_print_one_lock_resource(res);
> -		BUG();
> -	}
> -	return ret ? ret : r;
> +		if (r == -ENOMEM)
> +			BUG();
> +	} else
> +		ret = r;
> +
> +	return ret;
>  }
>  
>  int dlm_deref_lockres_handler(struct o2net_msg *msg, u32 len, void *data,
> diff --git a/fs/ocfs2/dlm/dlmthread.c b/fs/ocfs2/dlm/dlmthread.c
> index 68d239b..ce39722 100644
> --- a/fs/ocfs2/dlm/dlmthread.c
> +++ b/fs/ocfs2/dlm/dlmthread.c
> @@ -175,6 +175,15 @@ static void dlm_purge_lockres(struct dlm_ctxt *dlm,
>  	     res->lockname.len, res->lockname.name, master);
>  
>  	if (!master) {
> +		if (res->state & DLM_LOCK_RES_DROPPING_REF) {
> +			mlog(ML_NOTICE, "%s: res %.*s already in "
> +				"DLM_LOCK_RES_DROPPING_REF state\n",
> +				dlm->name, res->lockname.len,
> +				res->lockname.name);
> +			spin_unlock(&res->spinlock);
> +			return;
> +		}
> +
>  		res->state |= DLM_LOCK_RES_DROPPING_REF;
>  		/* drop spinlock...  retake below */
>  		spin_unlock(&res->spinlock);
> @@ -203,8 +212,8 @@ static void dlm_purge_lockres(struct dlm_ctxt *dlm,
>  		dlm->purge_count--;
>  	}
>  
> -	if (!master && ret != 0) {
> -		mlog(0, "%s: deref %.*s in progress or master goes down\n",
> +	if (!master && ret == DLM_DEREF_RESPONSE_INPROG) {
> +		mlog(0, "%s: deref %.*s in progress\n",
>  			dlm->name, res->lockname.len, res->lockname.name);
>  		spin_unlock(&res->spinlock);
>  		return;
>