Add list_move() support function for list manipulation.

WHATS_NEW

@@ -1,6 +1,7 @@
 Version 2.02.34 -
 ===================================
-  Add 'is_reserved_lvname()' helper function.
+  Add list_move() for moving elements from one list to another.
+  Add 'is_reserved_lvname()' for identifying hidden LVs.
   Correct command name in lvmdiskscan man page.
   clvmd no longer crashes if it sees nodeids over 50.
   Fix potential deadlock in clvmd thread handling.

lib/datastruct/list.h

@@ -54,6 +54,16 @@ void list_add_h(struct list *head, struct list *elem);
  */
 void list_del(struct list *elem);
 
+/*
+ * Move an element from an existing list to list 'head'.
+ * Insert the element before 'head'.
+ */
+static inline void list_move(struct list *item, struct list *head)
+{
+        list_del(item);
+        list_add(head, item);
+}
+
 /*
  * Is the list empty?
  */

libdm/datastruct/list.h

@@ -54,6 +54,16 @@ void list_add_h(struct list *head, struct list *elem);
  */
 void list_del(struct list *elem);
 
+/*
+ * Move an element from an existing list to list 'head'.
+ * Insert the element before 'head'.
+ */
+static inline void list_move(struct list *item, struct list *head)
+{
+        list_del(item);
+        list_add(head, item);
+}
+
 /*
  * Is the list empty?
  */