ocfs2: Increment the reference count of an already-active stack.

The ocfs2_stack_driver_request() function failed to increment the
refcount of an already-active stack.  It only did the increment on the
first reference.  Whoops.
Signed-off-by: Joel Becker <joel.becker@oracle.com>
Tested-by: Marcos Matsunaga <marcos.matsunaga@oracle.com>
Signed-off-by: Mark Fasheh <mfasheh@suse.com>

fs/ocfs2/stackglue.c

@@ -97,13 +97,14 @@ static int ocfs2_stack_driver_request(const char *stack_name,
 		goto out;
 	}
 
-	/* Ok, the stack is pinned */
-	p->sp_count++;
 	active_stack = p;
-
 	rc = 0;
 
 out:
+	/* If we found it, pin it */
+	if (!rc)
+		active_stack->sp_count++;
+
 	spin_unlock(&ocfs2_stack_lock);
 	return rc;
 }