[PATCH] list.h: add list_for_each_struct_entry macro

[Jiri Pirko <jpirko@redhat.com>]

When preparing to upcoming migration of mc_list (list of multicast MACs)
to list_head, the need of traversing the list over one structure member
appeared. I thought I'll do it locally but I decided that an intruduction
the macro in list.h would be much clearer. Please kindly for a review.

Jirka

Signed-off-by: Jiri Pirko <jpirko@redhat.com>

diff --git a/include/linux/list.h b/include/linux/list.h
index 969f6e9..8350a94 100644
--- a/include/linux/list.h
+++ b/include/linux/list.h
@@ -420,6 +420,22 @@ static inline void list_splice_tail_init(struct list_head *list,
 	     pos = list_entry(pos->member.prev, typeof(*pos), member))
 
 /**
+ * list_for_each_struct_entry  -       iterate over list of given type using
+ *                                     the struct member.
+ * @pos:       the type * to use as a loop cursor.
+ * @head:      the head for your list.
+ * @type:      the type of the struct.
+ * @posmember: the name ot the loop cursor within the struct.
+ * @member:    the name of the list_struct within the struct.
+ */
+#define list_for_each_struct_entry(pos, head, type, posmember, member)		\
+	for (pos = list_entry((head)->next, type, member)->posmember;		\
+	     prefetch(container_of(pos, type, posmember)->member.next),		\
+	     &container_of(pos, type, posmember)->member != (head);		\
+	     pos = list_entry(container_of(pos, type, posmember)->member.next,	\
+	     type, member)->posmember)
+
+/**
  * list_prepare_entry - prepare a pos entry for use in list_for_each_entry_continue()
  * @pos:	the type * to use as a start point
  * @head:	the head of the list