[PATCH 1/2] list: introduce list_bulk_move_tail helper

["Christian König" <ckoenig.leichtzumerken@gmail.com>]

Move all entries between @first and including @last before @head.

This is useful for LRU lists where a whole block of entries should be
moved to the end of an list.

Signed-off-by: Christian König <christian.koenig@amd.com>
---
 include/linux/list.h | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/include/linux/list.h b/include/linux/list.h
index de04cc5ed536..edb7628e46ed 100644
--- a/include/linux/list.h
+++ b/include/linux/list.h
@@ -183,6 +183,29 @@ static inline void list_move_tail(struct list_head *list,
 	list_add_tail(list, head);
 }
 
+/**
+ * list_bulk_move_tail - move a subsection of a list to its tail
+ * @head: the head that will follow our entry
+ * @first: first entry to move
+ * @last: last entry to move, can be the same as first
+ *
+ * Move all entries between @first and including @last before @head.
+ * All three entries must belong to the same linked list.
+ */
+static inline void list_bulk_move_tail(struct list_head *head,
+				       struct list_head *first,
+				       struct list_head *last)
+{
+	first->prev->next = last->next;
+	last->next->prev = first->prev;
+
+	head->prev->next = first;
+	first->prev = head->prev;
+
+	last->next = head;
+	head->prev = last;
+}
+
 /**
  * list_is_last - tests whether @list is the last entry in list @head
  * @list: the entry to test
-- 
2.14.1