ocfs2: give the dlm dirty list a reference on the lockres

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

fs/ocfs2/dlm/dlmcommon.h

@@ -235,18 +235,26 @@ struct dlm_lock_resource
 	struct qstr lockname;
 	struct kref      refs;
 
-	/* please keep these next 3 in this order
-	 * some funcs want to iterate over all lists */
+	/*
+	 * Please keep granted, converting, and blocked in this order,
+	 * as some funcs want to iterate over all lists.
+	 *
+	 * All four lists are protected by the hash's reference.
+	 */
 	struct list_head granted;
 	struct list_head converting;
 	struct list_head blocked;
+	struct list_head purge;
 
+	/*
+	 * These two lists require you to hold an additional reference
+	 * while they are on the list.
+	 */
 	struct list_head dirty;
 	struct list_head recovering; // dlm_recovery_ctxt.resources list
 
 	/* unused lock resources have their last_used stamped and are
 	 * put on a list for the dlm thread to run. */
-	struct list_head purge;
 	unsigned long    last_used;
 
 	unsigned migration_pending:1;

fs/ocfs2/dlm/dlmthread.c

@@ -455,6 +455,8 @@ void __dlm_dirty_lockres(struct dlm_ctxt *dlm, struct dlm_lock_resource *res)
 	/* don't shuffle secondary queues */
 	if ((res->owner == dlm->node_num) &&
 	    !(res->state & DLM_LOCK_RES_DIRTY)) {
+		/* ref for dirty_list */
+		dlm_lockres_get(res);
 		list_add_tail(&res->dirty, &dlm->dirty_list);
 		res->state |= DLM_LOCK_RES_DIRTY;
 	}
@@ -639,6 +641,8 @@ static int dlm_thread(void *data)
 			list_del_init(&res->dirty);
 			spin_unlock(&res->spinlock);
 			spin_unlock(&dlm->spinlock);
+			/* Drop dirty_list ref */
+			dlm_lockres_put(res);
 
 		 	/* lockres can be re-dirtied/re-added to the
 			 * dirty_list in this gap, but that is ok */
@@ -691,6 +695,8 @@ static int dlm_thread(void *data)
 			/* if the lock was in-progress, stick
 			 * it on the back of the list */
 			if (delay) {
+				/* ref for dirty_list */
+				dlm_lockres_get(res);
 				spin_lock(&res->spinlock);
 				list_add_tail(&res->dirty, &dlm->dirty_list);
 				res->state |= DLM_LOCK_RES_DIRTY;