[Ocfs2-devel] [PATCH] ocfs2/dlm: avoid incorrect bit set in refmap on recovery master

[Sunil Mushran]

Acked-by: Sunil Mushran <sunil.mushran at oracle.com>

On 07/30/2010 01:14 AM, Wengang Wang wrote:
> In the following situation, there remains an incorrect bit in refmap on the
> recovery master. Finally the recovery master will fail at purging the lockres
> due to the incorrect bit in refmap.
>
> 1) node A has no interest on lockres A any longer, so it is purging it.
> 2) the owner of lockres A is node B, so node A is sending de-ref message
> to node B.
> 3) at this time, node B crashed. node C becomes the recovery master. it recovers
> lockres A(because the master is the dead node B).
> 4) node A migrated lockres A to node C with a refbit there.
> 5) node A failed to send de-ref message to node B because it crashed. The failure
> is ignored. no other action is done for lockres A any more.
>
> For mormal, re-send the deref message to it to recovery master can fix it. Well,
> ignoring the failure of deref to the original master and not recovering the lockres
> to recovery master has the same effect. And the later is simpler.
>
> Signed-off-by: Wengang Wang<wen.gang.wang at oracle.com>
> Acked-by: Srinivas Eeda<srinivas.eeda at oracle.com>
> ---
>   fs/ocfs2/dlm/dlmrecovery.c |   22 ++++++++++------------
>   fs/ocfs2/dlm/dlmthread.c   |   34 +++++++++++++++++++++-------------
>   2 files changed, 31 insertions(+), 25 deletions(-)
>
> diff --git a/fs/ocfs2/dlm/dlmrecovery.c b/fs/ocfs2/dlm/dlmrecovery.c
> index 9dfaac7..aaaffbc 100644
> --- a/fs/ocfs2/dlm/dlmrecovery.c
> +++ b/fs/ocfs2/dlm/dlmrecovery.c
> @@ -1997,6 +1997,8 @@ void dlm_move_lockres_to_recovery_list(struct dlm_ctxt *dlm,
>   	struct list_head *queue;
>   	struct dlm_lock *lock, *next;
>
> +	assert_spin_locked(&dlm->spinlock);
> +	assert_spin_locked(&res->spinlock);
>   	res->state |= DLM_LOCK_RES_RECOVERING;
>   	if (!list_empty(&res->recovering)) {
>   		mlog(0,
> @@ -2326,19 +2328,15 @@ static void dlm_do_local_recovery_cleanup(struct dlm_ctxt *dlm, u8 dead_node)
>   			/* zero the lvb if necessary */
>   			dlm_revalidate_lvb(dlm, res, dead_node);
>   			if (res->owner == dead_node) {
> -				if (res->state&  DLM_LOCK_RES_DROPPING_REF)
> -					mlog(0, "%s:%.*s: owned by "
> -					     "dead node %u, this node was "
> -					     "dropping its ref when it died. "
> -					     "continue, dropping the flag.\n",
> -					     dlm->name, res->lockname.len,
> -					     res->lockname.name, dead_node);
> -
> -				/* the wake_up for this will happen when the
> -				 * RECOVERING flag is dropped later */
> -				res->state&= ~DLM_LOCK_RES_DROPPING_REF;
> +				if (res->state&  DLM_LOCK_RES_DROPPING_REF) {
> +					mlog(ML_NOTICE, "Ignore %.*s for "
> +					     "recovery as it is being freed\n",
> +					     res->lockname.len,
> +					     res->lockname.name);
> +				} else
> +					dlm_move_lockres_to_recovery_list(dlm,
> +									  res);
>
> -				dlm_move_lockres_to_recovery_list(dlm, res);
>   			} else if (res->owner == dlm->node_num) {
>   				dlm_free_dead_locks(dlm, res, dead_node);
>   				__dlm_lockres_calc_usage(dlm, res);
> diff --git a/fs/ocfs2/dlm/dlmthread.c b/fs/ocfs2/dlm/dlmthread.c
> index dd78ca3..c737021 100644
> --- a/fs/ocfs2/dlm/dlmthread.c
> +++ b/fs/ocfs2/dlm/dlmthread.c
> @@ -92,19 +92,27 @@ int __dlm_lockres_has_locks(struct dlm_lock_resource *res)
>    * truly ready to be freed. */
>   int __dlm_lockres_unused(struct dlm_lock_resource *res)
>   {
> -	if (!__dlm_lockres_has_locks(res)&&
> -	    (list_empty(&res->dirty)&&  !(res->state&  DLM_LOCK_RES_DIRTY))) {
> -		/* try not to scan the bitmap unless the first two
> -		 * conditions are already true */
> -		int bit = find_next_bit(res->refmap, O2NM_MAX_NODES, 0);
> -		if (bit>= O2NM_MAX_NODES) {
> -			/* since the bit for dlm->node_num is not
> -			 * set, inflight_locks better be zero */
> -			BUG_ON(res->inflight_locks != 0);
> -			return 1;
> -		}
> -	}
> -	return 0;
> +	int bit;
> +
> +	if (__dlm_lockres_has_locks(res))
> +		return 0;
> +
> +	if (!list_empty(&res->dirty) || res->state&  DLM_LOCK_RES_DIRTY)
> +		return 0;
> +
> +	if (res->state&  DLM_LOCK_RES_RECOVERING)
> +		return 0;
> +
> +	bit = find_next_bit(res->refmap, O2NM_MAX_NODES, 0);
> +	if (bit<  O2NM_MAX_NODES)
> +		return 0;
> +
> +	/*
> +	 * since the bit for dlm->node_num is not set, inflight_locks better
> +	 * be zero
> +	 */
> +	BUG_ON(res->inflight_locks != 0);
> +	return 1;
>   }
>
>
>