Introduce a handy list_first_entry macro

There are many places in the kernel where the construction like

   foo = list_entry(head->next, struct foo_struct, list);

are used.
The code might look more descriptive and neat if using the macro

   list_first_entry(head, type, member) \
             list_entry((head)->next, type, member)

Here is the macro itself and the examples of its usage in the generic code.
 If it will turn out to be useful, I can prepare the set of patches to
inject in into arch-specific code, drivers, networking, etc.

Signed-off-by: Pavel Emelianov <[email protected]>
Signed-off-by: Kirill Korotaev <[email protected]>
Cc: Randy Dunlap <[email protected]>
Cc: Andi Kleen <[email protected]>
Cc: Zach Brown <[email protected]>
Cc: Davide Libenzi <[email protected]>
Cc: John McCutchan <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: john stultz <[email protected]>
Cc: Ram Pai <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

1 files changed, 11 insertions, 0 deletions

diff --git a/include/linux/list.h b/include/linux/list.h
index f9d71eab05ee..9202703be2a4 100644
--- a/include/linux/list.h
+++ b/include/linux/list.h
@@ -426,6 +426,17 @@ static inline void list_splice_init_rcu(struct list_head *list,
 	container_of(ptr, type, member)
 
 /**
+ * list_first_entry - get the first element from a list
+ * @ptr:	the list head to take the element from.
+ * @type:	the type of the struct this is embedded in.
+ * @member:	the name of the list_struct within the struct.
+ *
+ * Note, that list is expected to be not empty.
+ */
+#define list_first_entry(ptr, type, member) \
+	list_entry((ptr)->next, type, member)
+
+/**
  * list_for_each	-	iterate over a list
  * @pos:	the &struct list_head to use as a loop cursor.
  * @head:	the head for your list.