ocfs2_dlm: fix cluster-wide refcounting of lock resources

This was previously broken and migration of some locks had to be temporarily
disabled. We use a new (and backward-incompatible) set of network messages
to account for all references to a lock resources held across the cluster.
once these are all freed, the master node may then free the lock resource
memory once its local references are dropped.

Signed-off-by: Kurt Hackel <kurt.hackel@oracle.com>
Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>

fs/ocfs2/dlm/dlmmaster.c

@@ -99,9 +99,9 @@ static void dlm_mle_node_up(struct dlm_ctxt *dlm,
 			    int idx);
 
 static void dlm_assert_master_worker(struct dlm_work_item *item, void *data);
-static int dlm_do_assert_master(struct dlm_ctxt *dlm, const char *lockname,
-				unsigned int namelen, void *nodemap,
-				u32 flags);
+static int dlm_do_assert_master(struct dlm_ctxt *dlm,
+				struct dlm_lock_resource *res,
+				void *nodemap, u32 flags);
 
 static inline int dlm_mle_equal(struct dlm_ctxt *dlm,
 				struct dlm_master_list_entry *mle,
@@ -237,7 +237,8 @@ static int dlm_find_mle(struct dlm_ctxt *dlm,
 			struct dlm_master_list_entry **mle,
 			char *name, unsigned int namelen);
 
-static int dlm_do_master_request(struct dlm_master_list_entry *mle, int to);
+static int dlm_do_master_request(struct dlm_lock_resource *res,
+				 struct dlm_master_list_entry *mle, int to);
 
 
 static int dlm_wait_for_lock_mastery(struct dlm_ctxt *dlm,
@@ -687,6 +688,7 @@ static void dlm_init_lockres(struct dlm_ctxt *dlm,
 	INIT_LIST_HEAD(&res->purge);
 	atomic_set(&res->asts_reserved, 0);
 	res->migration_pending = 0;
+	res->inflight_locks = 0;
 
 	kref_init(&res->refs);
 
@@ -700,6 +702,7 @@ static void dlm_init_lockres(struct dlm_ctxt *dlm,
 	res->last_used = 0;
 
 	memset(res->lvb, 0, DLM_LVB_LEN);
+	memset(res->refmap, 0, sizeof(res->refmap));
 }
 
 struct dlm_lock_resource *dlm_new_lockres(struct dlm_ctxt *dlm,
@@ -722,6 +725,42 @@ struct dlm_lock_resource *dlm_new_lockres(struct dlm_ctxt *dlm,
 	return res;
 }
 
+void __dlm_lockres_grab_inflight_ref(struct dlm_ctxt *dlm,
+				   struct dlm_lock_resource *res,
+				   int new_lockres,
+				   const char *file,
+				   int line)
+{
+	if (!new_lockres)
+		assert_spin_locked(&res->spinlock);
+
+	if (!test_bit(dlm->node_num, res->refmap)) {
+		BUG_ON(res->inflight_locks != 0);
+		dlm_lockres_set_refmap_bit(dlm->node_num, res);
+	}
+	res->inflight_locks++;
+	mlog(0, "%s:%.*s: inflight++: now %u\n",
+	     dlm->name, res->lockname.len, res->lockname.name,
+	     res->inflight_locks);
+}
+
+void __dlm_lockres_drop_inflight_ref(struct dlm_ctxt *dlm,
+				   struct dlm_lock_resource *res,
+				   const char *file,
+				   int line)
+{
+	assert_spin_locked(&res->spinlock);
+
+	BUG_ON(res->inflight_locks == 0);
+	res->inflight_locks--;
+	mlog(0, "%s:%.*s: inflight--: now %u\n",
+	     dlm->name, res->lockname.len, res->lockname.name,
+	     res->inflight_locks);
+	if (res->inflight_locks == 0)
+		dlm_lockres_clear_refmap_bit(dlm->node_num, res);
+	wake_up(&res->wq);
+}
+
 /*
  * lookup a lock resource by name.
  * may already exist in the hashtable.
@@ -752,6 +791,7 @@ struct dlm_lock_resource * dlm_get_lock_resource(struct dlm_ctxt *dlm,
 	unsigned int hash;
 	int tries = 0;
 	int bit, wait_on_recovery = 0;
+	int drop_inflight_if_nonlocal = 0;
 
 	BUG_ON(!lockid);
 
@@ -761,9 +801,30 @@ struct dlm_lock_resource * dlm_get_lock_resource(struct dlm_ctxt *dlm,
 
 lookup:
 	spin_lock(&dlm->spinlock);
-	tmpres = __dlm_lookup_lockres(dlm, lockid, namelen, hash);
+	tmpres = __dlm_lookup_lockres_full(dlm, lockid, namelen, hash);
 	if (tmpres) {
+		int dropping_ref = 0;
+
+		spin_lock(&tmpres->spinlock);
+		if (tmpres->owner == dlm->node_num) {
+			BUG_ON(tmpres->state & DLM_LOCK_RES_DROPPING_REF);
+			dlm_lockres_grab_inflight_ref(dlm, tmpres);
+		} else if (tmpres->state & DLM_LOCK_RES_DROPPING_REF)
+			dropping_ref = 1;
+		spin_unlock(&tmpres->spinlock);
 		spin_unlock(&dlm->spinlock);
+
+		/* wait until done messaging the master, drop our ref to allow
+		 * the lockres to be purged, start over. */
+		if (dropping_ref) {
+			spin_lock(&tmpres->spinlock);
+			__dlm_wait_on_lockres_flags(tmpres, DLM_LOCK_RES_DROPPING_REF);
+			spin_unlock(&tmpres->spinlock);
+			dlm_lockres_put(tmpres);
+			tmpres = NULL;
+			goto lookup;
+		}
+
 		mlog(0, "found in hash!\n");
 		if (res)
 			dlm_lockres_put(res);
@@ -793,6 +854,7 @@ lookup:
 		spin_lock(&res->spinlock);
 		dlm_change_lockres_owner(dlm, res, dlm->node_num);
 		__dlm_insert_lockres(dlm, res);
+		dlm_lockres_grab_inflight_ref(dlm, res);
 		spin_unlock(&res->spinlock);
 		spin_unlock(&dlm->spinlock);
 		/* lockres still marked IN_PROGRESS */
@@ -805,29 +867,40 @@ lookup:
 	/* if we found a block, wait for lock to be mastered by another node */
 	blocked = dlm_find_mle(dlm, &mle, (char *)lockid, namelen);
 	if (blocked) {
+		int mig;
 		if (mle->type == DLM_MLE_MASTER) {
 			mlog(ML_ERROR, "master entry for nonexistent lock!\n");
 			BUG();
-		} else if (mle->type == DLM_MLE_MIGRATION) {
-			/* migration is in progress! */
-			/* the good news is that we now know the
-			 * "current" master (mle->master). */
-
+		}
+		mig = (mle->type == DLM_MLE_MIGRATION);
+		/* if there is a migration in progress, let the migration
+		 * finish before continuing.  we can wait for the absence
+		 * of the MIGRATION mle: either the migrate finished or
+		 * one of the nodes died and the mle was cleaned up.
+		 * if there is a BLOCK here, but it already has a master
+		 * set, we are too late.  the master does not have a ref
+		 * for us in the refmap.  detach the mle and drop it.
+		 * either way, go back to the top and start over. */
+		if (mig || mle->master != O2NM_MAX_NODES) {
+			BUG_ON(mig && mle->master == dlm->node_num);
+			/* we arrived too late.  the master does not
+			 * have a ref for us. retry. */
+			mlog(0, "%s:%.*s: late on %s\n",
+			     dlm->name, namelen, lockid,
+			     mig ?  "MIGRATION" : "BLOCK");
 			spin_unlock(&dlm->master_lock);
-			assert_spin_locked(&dlm->spinlock);
-
-			/* set the lockres owner and hash it */
-			spin_lock(&res->spinlock);
-			dlm_set_lockres_owner(dlm, res, mle->master);
-			__dlm_insert_lockres(dlm, res);
-			spin_unlock(&res->spinlock);
 			spin_unlock(&dlm->spinlock);
 
 			/* master is known, detach */
-			dlm_mle_detach_hb_events(dlm, mle);
+			if (!mig)
+				dlm_mle_detach_hb_events(dlm, mle);
 			dlm_put_mle(mle);
 			mle = NULL;
-			goto wake_waiters;
+			/* this is lame, but we cant wait on either
+			 * the mle or lockres waitqueue here */
+			if (mig)
+				msleep(100);
+			goto lookup;
 		}
 	} else {
 		/* go ahead and try to master lock on this node */
@@ -858,6 +931,13 @@ lookup:
 
 	/* finally add the lockres to its hash bucket */
 	__dlm_insert_lockres(dlm, res);
+	/* since this lockres is new it doesnt not require the spinlock */
+	dlm_lockres_grab_inflight_ref_new(dlm, res);
+
+	/* if this node does not become the master make sure to drop
+	 * this inflight reference below */
+	drop_inflight_if_nonlocal = 1;
+
 	/* get an extra ref on the mle in case this is a BLOCK
 	 * if so, the creator of the BLOCK may try to put the last
 	 * ref at this time in the assert master handler, so we
@@ -910,7 +990,7 @@ redo_request:
 	ret = -EINVAL;
 	dlm_node_iter_init(mle->vote_map, &iter);
 	while ((nodenum = dlm_node_iter_next(&iter)) >= 0) {
-		ret = dlm_do_master_request(mle, nodenum);
+		ret = dlm_do_master_request(res, mle, nodenum);
 		if (ret < 0)
 			mlog_errno(ret);
 		if (mle->master != O2NM_MAX_NODES) {
@@ -960,6 +1040,8 @@ wait:
 
 wake_waiters:
 	spin_lock(&res->spinlock);
+	if (res->owner != dlm->node_num && drop_inflight_if_nonlocal)
+		dlm_lockres_drop_inflight_ref(dlm, res);
 	res->state &= ~DLM_LOCK_RES_IN_PROGRESS;
 	spin_unlock(&res->spinlock);
 	wake_up(&res->wq);
@@ -998,7 +1080,7 @@ recheck:
 		/* this will cause the master to re-assert across
 		 * the whole cluster, freeing up mles */
 		if (res->owner != dlm->node_num) {
-			ret = dlm_do_master_request(mle, res->owner);
+			ret = dlm_do_master_request(res, mle, res->owner);
 			if (ret < 0) {
 				/* give recovery a chance to run */
 				mlog(ML_ERROR, "link to %u went down?: %d\n", res->owner, ret);
@@ -1062,6 +1144,8 @@ recheck:
 			 	 * now tell other nodes that I am
 				 * mastering this. */
 				mle->master = dlm->node_num;
+				/* ref was grabbed in get_lock_resource
+				 * will be dropped in dlmlock_master */
 				assert = 1;
 				sleep = 0;
 			}
@@ -1087,7 +1171,8 @@ recheck:
 					 (atomic_read(&mle->woken) == 1),
 					 timeo);
 		if (res->owner == O2NM_MAX_NODES) {
-			mlog(0, "waiting again\n");
+			mlog(0, "%s:%.*s: waiting again\n", dlm->name,
+			     res->lockname.len, res->lockname.name);
 			goto recheck;
 		}
 		mlog(0, "done waiting, master is %u\n", res->owner);
@@ -1100,8 +1185,7 @@ recheck:
 		m = dlm->node_num;
 		mlog(0, "about to master %.*s here, this=%u\n",
 		     res->lockname.len, res->lockname.name, m);
-		ret = dlm_do_assert_master(dlm, res->lockname.name,
-					   res->lockname.len, mle->vote_map, 0);
+		ret = dlm_do_assert_master(dlm, res, mle->vote_map, 0);
 		if (ret) {
 			/* This is a failure in the network path,
 			 * not in the response to the assert_master
@@ -1117,6 +1201,8 @@ recheck:
 
 	/* set the lockres owner */
 	spin_lock(&res->spinlock);
+	/* mastery reference obtained either during
+	 * assert_master_handler or in get_lock_resource */
 	dlm_change_lockres_owner(dlm, res, m);
 	spin_unlock(&res->spinlock);
 
@@ -1283,7 +1369,8 @@ static int dlm_restart_lock_mastery(struct dlm_ctxt *dlm,
  *
  */
 
-static int dlm_do_master_request(struct dlm_master_list_entry *mle, int to)
+static int dlm_do_master_request(struct dlm_lock_resource *res,
+				 struct dlm_master_list_entry *mle, int to)
 {
 	struct dlm_ctxt *dlm = mle->dlm;
 	struct dlm_master_request request;
@@ -1339,6 +1426,9 @@ again:
 		case DLM_MASTER_RESP_YES:
 			set_bit(to, mle->response_map);
 			mlog(0, "node %u is the master, response=YES\n", to);
+			mlog(0, "%s:%.*s: master node %u now knows I have a "
+			     "reference\n", dlm->name, res->lockname.len,
+			     res->lockname.name, to);
 			mle->master = to;
 			break;
 		case DLM_MASTER_RESP_NO:
@@ -1428,8 +1518,10 @@ way_up_top:
 		}
 
 		if (res->owner == dlm->node_num) {
+			mlog(0, "%s:%.*s: setting bit %u in refmap\n",
+			     dlm->name, namelen, name, request->node_idx);
+			dlm_lockres_set_refmap_bit(request->node_idx, res);
 			spin_unlock(&res->spinlock);
-			// mlog(0, "this node is the master\n");
 			response = DLM_MASTER_RESP_YES;
 			if (mle)
 				kmem_cache_free(dlm_mle_cache, mle);
@@ -1477,7 +1569,6 @@ way_up_top:
 			mlog(0, "node %u is master, but trying to migrate to "
 			     "node %u.\n", tmpmle->master, tmpmle->new_master);
 			if (tmpmle->master == dlm->node_num) {
-				response = DLM_MASTER_RESP_YES;
 				mlog(ML_ERROR, "no owner on lockres, but this "
 				     "node is trying to migrate it to %u?!\n",
 				     tmpmle->new_master);
@@ -1494,6 +1585,10 @@ way_up_top:
 				 * go back and clean the mles on any
 				 * other nodes */
 				dispatch_assert = 1;
+				dlm_lockres_set_refmap_bit(request->node_idx, res);
+				mlog(0, "%s:%.*s: setting bit %u in refmap\n",
+				     dlm->name, namelen, name,
+				     request->node_idx);
 			} else
 				response = DLM_MASTER_RESP_NO;
 		} else {
@@ -1607,15 +1702,17 @@ send_response:
  * can periodically run all locks owned by this node
  * and re-assert across the cluster...
  */
-static int dlm_do_assert_master(struct dlm_ctxt *dlm, const char *lockname,
-				unsigned int namelen, void *nodemap,
-				u32 flags)
+int dlm_do_assert_master(struct dlm_ctxt *dlm,
+			 struct dlm_lock_resource *res,
+			 void *nodemap, u32 flags)
 {
 	struct dlm_assert_master assert;
 	int to, tmpret;
 	struct dlm_node_iter iter;
 	int ret = 0;
 	int reassert;
+	const char *lockname = res->lockname.name;
+	unsigned int namelen = res->lockname.len;
 
 	BUG_ON(namelen > O2NM_MAX_NAME_LEN);
 again:
@@ -1647,6 +1744,7 @@ again:
 			mlog(0, "link to %d went down!\n", to);
 			/* any nonzero status return will do */
 			ret = tmpret;
+			r = 0;
 		} else if (r < 0) {
 			/* ok, something horribly messed.  kill thyself. */
 			mlog(ML_ERROR,"during assert master of %.*s to %u, "
@@ -1661,12 +1759,29 @@ again:
 			spin_unlock(&dlm->master_lock);
 			spin_unlock(&dlm->spinlock);
 			BUG();
-		} else if (r == EAGAIN) {
+		}
+
+		if (r & DLM_ASSERT_RESPONSE_REASSERT &&
+		    !(r & DLM_ASSERT_RESPONSE_MASTERY_REF)) {
+				mlog(ML_ERROR, "%.*s: very strange, "
+				     "master MLE but no lockres on %u\n",
+				     namelen, lockname, to);
+		}
+
+		if (r & DLM_ASSERT_RESPONSE_REASSERT) {
 			mlog(0, "%.*s: node %u create mles on other "
 			     "nodes and requests a re-assert\n", 
 			     namelen, lockname, to);
 			reassert = 1;
 		}
+		if (r & DLM_ASSERT_RESPONSE_MASTERY_REF) {
+			mlog(0, "%.*s: node %u has a reference to this "
+			     "lockres, set the bit in the refmap\n",
+			     namelen, lockname, to);
+			spin_lock(&res->spinlock);
+			dlm_lockres_set_refmap_bit(to, res);
+			spin_unlock(&res->spinlock);
+		}
 	}
 
 	if (reassert)
@@ -1693,7 +1808,7 @@ int dlm_assert_master_handler(struct o2net_msg *msg, u32 len, void *data)
 	char *name;
 	unsigned int namelen, hash;
 	u32 flags;
-	int master_request = 0;
+	int master_request = 0, have_lockres_ref = 0;
 	int ret = 0;
 
 	if (!dlm_grab(dlm))
@@ -1864,6 +1979,7 @@ ok:
 				dlm_change_lockres_owner(dlm, res, mle->master);
 			}
 			spin_unlock(&res->spinlock);
+			have_lockres_ref = 1;
 		}
 
 		/* master is known, detach if not already detached.
@@ -1918,7 +2034,19 @@ done:
 	dlm_put(dlm);
 	if (master_request) {
 		mlog(0, "need to tell master to reassert\n");
-		ret = EAGAIN;  // positive. negative would shoot down the node.
+		/* positive. negative would shoot down the node. */
+		ret |= DLM_ASSERT_RESPONSE_REASSERT;
+		if (!have_lockres_ref) {
+			mlog(ML_ERROR, "strange, got assert from %u, MASTER "
+			     "mle present here for %s:%.*s, but no lockres!\n",
+			     assert->node_idx, dlm->name, namelen, name);
+		}
+	}
+	if (have_lockres_ref) {
+		/* let the master know we have a reference to the lockres */
+		ret |= DLM_ASSERT_RESPONSE_MASTERY_REF;
+		mlog(0, "%s:%.*s: got assert from %u, need a ref\n",
+		     dlm->name, namelen, name, assert->node_idx);
 	}
 	return ret;
 
@@ -2023,9 +2151,7 @@ static void dlm_assert_master_worker(struct dlm_work_item *item, void *data)
 	 * even if one or more nodes die */
 	mlog(0, "worker about to master %.*s here, this=%u\n",
 		     res->lockname.len, res->lockname.name, dlm->node_num);
-	ret = dlm_do_assert_master(dlm, res->lockname.name,
-				   res->lockname.len,
-				   nodemap, flags);
+	ret = dlm_do_assert_master(dlm, res, nodemap, flags);
 	if (ret < 0) {
 		/* no need to restart, we are done */
 		if (!dlm_is_host_down(ret))
@@ -2097,6 +2223,104 @@ static int dlm_pre_master_reco_lockres(struct dlm_ctxt *dlm,
 	return ret;
 }
 
+/*
+ * DLM_DEREF_LOCKRES_MSG
+ */
+
+int dlm_drop_lockres_ref(struct dlm_ctxt *dlm, struct dlm_lock_resource *res)
+{
+	struct dlm_deref_lockres deref;
+	int ret = 0, r;
+	const char *lockname;
+	unsigned int namelen;
+
+	lockname = res->lockname.name;
+	namelen = res->lockname.len;
+	BUG_ON(namelen > O2NM_MAX_NAME_LEN);
+
+	mlog(0, "%s:%.*s: sending deref to %d\n",
+	     dlm->name, namelen, lockname, res->owner);
+	memset(&deref, 0, sizeof(deref));
+	deref.node_idx = dlm->node_num;
+	deref.namelen = namelen;
+	memcpy(deref.name, lockname, namelen);
+
+	ret = o2net_send_message(DLM_DEREF_LOCKRES_MSG, dlm->key,
+				 &deref, sizeof(deref), res->owner, &r);
+	if (ret < 0)
+		mlog_errno(ret);
+	else if (r < 0) {
+		/* BAD.  other node says I did not have a ref. */
+		mlog(ML_ERROR,"while dropping ref on %s:%.*s "
+		    "(master=%u) got %d.\n", dlm->name, namelen,
+		    lockname, res->owner, r);
+		dlm_print_one_lock_resource(res);
+		BUG();
+	}
+	return ret;
+}
+
+int dlm_deref_lockres_handler(struct o2net_msg *msg, u32 len, void *data)
+{
+	struct dlm_ctxt *dlm = data;
+	struct dlm_deref_lockres *deref = (struct dlm_deref_lockres *)msg->buf;
+	struct dlm_lock_resource *res = NULL;
+	char *name;
+	unsigned int namelen;
+	int ret = -EINVAL;
+	u8 node;
+	unsigned int hash;
+
+	if (!dlm_grab(dlm))
+		return 0;
+
+	name = deref->name;
+	namelen = deref->namelen;
+	node = deref->node_idx;
+
+	if (namelen > DLM_LOCKID_NAME_MAX) {
+		mlog(ML_ERROR, "Invalid name length!");
+		goto done;
+	}
+	if (deref->node_idx >= O2NM_MAX_NODES) {
+		mlog(ML_ERROR, "Invalid node number: %u\n", node);
+		goto done;
+	}
+
+	hash = dlm_lockid_hash(name, namelen);
+
+	spin_lock(&dlm->spinlock);
+	res = __dlm_lookup_lockres_full(dlm, name, namelen, hash);
+	if (!res) {
+		spin_unlock(&dlm->spinlock);
+		mlog(ML_ERROR, "%s:%.*s: bad lockres name\n",
+		     dlm->name, namelen, name);
+		goto done;
+	}
+	spin_unlock(&dlm->spinlock);
+
+	spin_lock(&res->spinlock);
+	BUG_ON(res->state & DLM_LOCK_RES_DROPPING_REF);
+	if (test_bit(node, res->refmap)) {
+		ret = 0;
+		dlm_lockres_clear_refmap_bit(node, res);
+	} else {
+		mlog(ML_ERROR, "%s:%.*s: node %u trying to drop ref "
+		     "but it is already dropped!\n", dlm->name, namelen,
+		     name, node);
+		__dlm_print_one_lock_resource(res);
+	}
+	spin_unlock(&res->spinlock);
+
+	if (!ret)
+		dlm_lockres_calc_usage(dlm, res);
+done:
+	if (res)
+		dlm_lockres_put(res);
+	dlm_put(dlm);
+	return ret;
+}
+
 
 /*
  * DLM_MIGRATE_LOCKRES
@@ -2376,6 +2600,53 @@ leave:
 	return ret;
 }
 
+#define DLM_MIGRATION_RETRY_MS  100
+
+/* Should be called only after beginning the domain leave process.
+ * There should not be any remaining locks on nonlocal lock resources,
+ * and there should be no local locks left on locally mastered resources.
+ *
+ * Called with the dlm spinlock held, may drop it to do migration, but
+ * will re-acquire before exit.
+ *
+ * Returns: 1 if dlm->spinlock was dropped/retaken, 0 if never dropped */
+int dlm_empty_lockres(struct dlm_ctxt *dlm, struct dlm_lock_resource *res)
+{
+	int ret;
+	int lock_dropped = 0;
+
+	if (res->owner != dlm->node_num) {
+		if (!__dlm_lockres_unused(res)) {
+			mlog(ML_ERROR, "%s:%.*s: this node is not master, "
+			     "trying to free this but locks remain\n",
+			     dlm->name, res->lockname.len, res->lockname.name);
+		}
+		goto leave;
+	}
+
+	/* Wheee! Migrate lockres here! Will sleep so drop spinlock. */
+	spin_unlock(&dlm->spinlock);
+	lock_dropped = 1;
+	while (1) {
+		ret = dlm_migrate_lockres(dlm, res, O2NM_MAX_NODES);
+		if (ret >= 0)
+			break;
+		if (ret == -ENOTEMPTY) {
+			mlog(ML_ERROR, "lockres %.*s still has local locks!\n",
+		     		res->lockname.len, res->lockname.name);
+			BUG();
+		}
+
+		mlog(0, "lockres %.*s: migrate failed, "
+		     "retrying\n", res->lockname.len,
+		     res->lockname.name);
+		msleep(DLM_MIGRATION_RETRY_MS);
+	}
+	spin_lock(&dlm->spinlock);
+leave:
+	return lock_dropped;
+}
+
 int dlm_lock_basts_flushed(struct dlm_ctxt *dlm, struct dlm_lock *lock)
 {
 	int ret;
@@ -2490,7 +2761,7 @@ static void dlm_remove_nonlocal_locks(struct dlm_ctxt *dlm,
 {
 	struct list_head *iter, *iter2;
 	struct list_head *queue = &res->granted;
-	int i;
+	int i, bit;
 	struct dlm_lock *lock;
 
 	assert_spin_locked(&res->spinlock);
@@ -2508,12 +2779,28 @@ static void dlm_remove_nonlocal_locks(struct dlm_ctxt *dlm,
 				BUG_ON(!list_empty(&lock->bast_list));
 				BUG_ON(lock->ast_pending);
 				BUG_ON(lock->bast_pending);
+				dlm_lockres_clear_refmap_bit(lock->ml.node, res);
 				list_del_init(&lock->list);
 				dlm_lock_put(lock);
 			}
 		}
 		queue++;
 	}
+	bit = 0;
+	while (1) {
+		bit = find_next_bit(res->refmap, O2NM_MAX_NODES, bit);
+		if (bit >= O2NM_MAX_NODES)
+			break;
+		/* do not clear the local node reference, if there is a
+		 * process holding this, let it drop the ref itself */
+		if (bit != dlm->node_num) {
+			mlog(0, "%s:%.*s: node %u had a ref to this "
+			     "migrating lockres, clearing\n", dlm->name,
+			     res->lockname.len, res->lockname.name, bit);
+			dlm_lockres_clear_refmap_bit(bit, res);
+		}
+		bit++;
+	}
 }
 
 /* for now this is not too intelligent.  we will
@@ -2601,6 +2888,16 @@ static int dlm_do_migrate_request(struct dlm_ctxt *dlm,
 			mlog(0, "migrate request (node %u) returned %d!\n",
 			     nodenum, status);
 			ret = status;
+		} else if (status == DLM_MIGRATE_RESPONSE_MASTERY_REF) {
+			/* during the migration request we short-circuited
+			 * the mastery of the lockres.  make sure we have
+			 * a mastery ref for nodenum */
+			mlog(0, "%s:%.*s: need ref for node %u\n",
+			     dlm->name, res->lockname.len, res->lockname.name,
+			     nodenum);
+			spin_lock(&res->spinlock);
+			dlm_lockres_set_refmap_bit(nodenum, res);
+			spin_unlock(&res->spinlock);
 		}
 	}
 
@@ -2745,7 +3042,13 @@ static int dlm_add_migration_mle(struct dlm_ctxt *dlm,
 			/* remove it from the list so that only one
 			 * mle will be found */
 			list_del_init(&tmp->list);
-			__dlm_mle_detach_hb_events(dlm, mle);
+			/* this was obviously WRONG.  mle is uninited here.  should be tmp. */
+			__dlm_mle_detach_hb_events(dlm, tmp);
+			ret = DLM_MIGRATE_RESPONSE_MASTERY_REF;
+			mlog(0, "%s:%.*s: master=%u, newmaster=%u, "
+			    "telling master to get ref for cleared out mle "
+			    "during migration\n", dlm->name, namelen, name,
+			    master, new_master);
 		}
 		spin_unlock(&tmp->spinlock);
 	}
@@ -2753,6 +3056,8 @@ static int dlm_add_migration_mle(struct dlm_ctxt *dlm,
 	/* now add a migration mle to the tail of the list */
 	dlm_init_mle(mle, DLM_MLE_MIGRATION, dlm, res, name, namelen);
 	mle->new_master = new_master;
+	/* the new master will be sending an assert master for this.
+	 * at that point we will get the refmap reference */
 	mle->master = master;
 	/* do this for consistency with other mle types */
 	set_bit(new_master, mle->maybe_map);
@@ -2902,6 +3207,13 @@ int dlm_finish_migration(struct dlm_ctxt *dlm, struct dlm_lock_resource *res,
 	clear_bit(dlm->node_num, iter.node_map);
 	spin_unlock(&dlm->spinlock);
 
+	/* ownership of the lockres is changing.  account for the
+	 * mastery reference here since old_master will briefly have
+	 * a reference after the migration completes */
+	spin_lock(&res->spinlock);
+	dlm_lockres_set_refmap_bit(old_master, res);
+	spin_unlock(&res->spinlock);
+
 	mlog(0, "now time to do a migrate request to other nodes\n");
 	ret = dlm_do_migrate_request(dlm, res, old_master,
 				     dlm->node_num, &iter);
@@ -2914,8 +3226,7 @@ int dlm_finish_migration(struct dlm_ctxt *dlm, struct dlm_lock_resource *res,
 	     res->lockname.len, res->lockname.name);
 	/* this call now finishes out the nodemap
 	 * even if one or more nodes die */
-	ret = dlm_do_assert_master(dlm, res->lockname.name,
-				   res->lockname.len, iter.node_map,
+	ret = dlm_do_assert_master(dlm, res, iter.node_map,
 				   DLM_ASSERT_MASTER_FINISH_MIGRATION);
 	if (ret < 0) {
 		/* no longer need to retry.  all living nodes contacted. */
@@ -2927,8 +3238,7 @@ int dlm_finish_migration(struct dlm_ctxt *dlm, struct dlm_lock_resource *res,
 	set_bit(old_master, iter.node_map);
 	mlog(0, "doing assert master of %.*s back to %u\n",
 	     res->lockname.len, res->lockname.name, old_master);
-	ret = dlm_do_assert_master(dlm, res->lockname.name,
-				   res->lockname.len, iter.node_map,
+	ret = dlm_do_assert_master(dlm, res, iter.node_map,
 				   DLM_ASSERT_MASTER_FINISH_MIGRATION);
 	if (ret < 0) {
 		mlog(0, "assert master to original master failed "