ocfs2_dlm: Ensure correct ordering of set/clear refmap bit on lockres

Eventhough the set refmap bit message is sent before the clear refmap
message, currently there is no guarentee that the set message will be
handled before the clear. This patch prevents the clear refmap to be
processed while the node is sending assert master messages to other
nodes. (The set refmap message is sent as a response to the assert
master request).

Signed-off-by: Sunil Mushran <sunil.mushran@oracle.com>
Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>

fs/ocfs2/dlm/dlmcommon.h

@@ -180,6 +180,11 @@ struct dlm_assert_master_priv
 	unsigned ignore_higher:1;
 };
 
+struct dlm_deref_lockres_priv
+{
+	struct dlm_lock_resource *deref_res;
+	u8 deref_node;
+};
 
 struct dlm_work_item
 {
@@ -191,6 +196,7 @@ struct dlm_work_item
 		struct dlm_request_all_locks_priv ral;
 		struct dlm_mig_lockres_priv ml;
 		struct dlm_assert_master_priv am;
+		struct dlm_deref_lockres_priv dl;
 	} u;
 };
 

fs/ocfs2/dlm/dlmmaster.c

@@ -102,6 +102,7 @@ static void dlm_assert_master_worker(struct dlm_work_item *item, void *data);
 static int dlm_do_assert_master(struct dlm_ctxt *dlm,
 				struct dlm_lock_resource *res,
 				void *nodemap, u32 flags);
+static void dlm_deref_lockres_worker(struct dlm_work_item *item, void *data);
 
 static inline int dlm_mle_equal(struct dlm_ctxt *dlm,
 				struct dlm_master_list_entry *mle,
@@ -1717,6 +1718,11 @@ int dlm_do_assert_master(struct dlm_ctxt *dlm,
 	unsigned int namelen = res->lockname.len;
 
 	BUG_ON(namelen > O2NM_MAX_NAME_LEN);
+
+	spin_lock(&res->spinlock);
+	res->state |= DLM_LOCK_RES_SETREF_INPROG;
+	spin_unlock(&res->spinlock);
+
 again:
 	reassert = 0;
 
@@ -1789,6 +1795,11 @@ int dlm_do_assert_master(struct dlm_ctxt *dlm,
 	if (reassert)
 		goto again;
 
+	spin_lock(&res->spinlock);
+	res->state &= ~DLM_LOCK_RES_SETREF_INPROG;
+	spin_unlock(&res->spinlock);
+	wake_up(&res->wq);
+
 	return ret;
 }
 
@@ -2296,6 +2307,9 @@ int dlm_deref_lockres_handler(struct o2net_msg *msg, u32 len, void *data,
 	int ret = -EINVAL;
 	u8 node;
 	unsigned int hash;
+	struct dlm_work_item *item;
+	int cleared = 0;
+	int dispatch = 0;
 
 	if (!dlm_grab(dlm))
 		return 0;
@@ -2326,27 +2340,90 @@ int dlm_deref_lockres_handler(struct o2net_msg *msg, u32 len, void *data,
 	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);
+	if (res->state & DLM_LOCK_RES_SETREF_INPROG)
+		dispatch = 1;
+	else {
+		BUG_ON(res->state & DLM_LOCK_RES_DROPPING_REF);
+		if (test_bit(node, res->refmap)) {
+			dlm_lockres_clear_refmap_bit(node, res);
+			cleared = 1;
+		}
 	}
 	spin_unlock(&res->spinlock);
 
-	if (!ret)
-		dlm_lockres_calc_usage(dlm, res);
+	if (!dispatch) {
+		if (cleared)
+			dlm_lockres_calc_usage(dlm, res);
+		else {
+			mlog(ML_ERROR, "%s:%.*s: node %u trying to drop ref "
+		     	"but it is already dropped!\n", dlm->name,
+		     	res->lockname.len, res->lockname.name, node);
+			__dlm_print_one_lock_resource(res);
+		}
+		ret = 0;
+		goto done;
+	}
+
+	item = kzalloc(sizeof(*item), GFP_NOFS);
+	if (!item) {
+		ret = -ENOMEM;
+		mlog_errno(ret);
+		goto done;
+	}
+
+	dlm_init_work_item(dlm, item, dlm_deref_lockres_worker, NULL);
+	item->u.dl.deref_res = res;
+	item->u.dl.deref_node = node;
+
+	spin_lock(&dlm->work_lock);
+	list_add_tail(&item->list, &dlm->work_list);
+	spin_unlock(&dlm->work_lock);
+
+	queue_work(dlm->dlm_worker, &dlm->dispatched_work);
+	return 0;
+
 done:
 	if (res)
 		dlm_lockres_put(res);
 	dlm_put(dlm);
+
 	return ret;
 }
 
+static void dlm_deref_lockres_worker(struct dlm_work_item *item, void *data)
+{
+	struct dlm_ctxt *dlm;
+	struct dlm_lock_resource *res;
+	u8 node;
+	u8 cleared = 0;
+
+	dlm = item->dlm;
+	res = item->u.dl.deref_res;
+	node = item->u.dl.deref_node;
+
+	spin_lock(&res->spinlock);
+	BUG_ON(res->state & DLM_LOCK_RES_DROPPING_REF);
+	if (test_bit(node, res->refmap)) {
+		__dlm_wait_on_lockres_flags(res, DLM_LOCK_RES_SETREF_INPROG);
+		dlm_lockres_clear_refmap_bit(node, res);
+		cleared = 1;
+	}
+	spin_unlock(&res->spinlock);
+
+	if (cleared) {
+		mlog(0, "%s:%.*s node %u ref dropped in dispatch\n",
+		     dlm->name, res->lockname.len, res->lockname.name, node);
+		dlm_lockres_calc_usage(dlm, res);
+	} else {
+		mlog(ML_ERROR, "%s:%.*s: node %u trying to drop ref "
+		     "but it is already dropped!\n", dlm->name,
+		     res->lockname.len, res->lockname.name, node);
+		__dlm_print_one_lock_resource(res);
+	}
+
+	dlm_lockres_put(res);
+}
+
 
 /*
  * DLM_MIGRATE_LOCKRES