list: introduce list_first_entry_or_null

commit 6d7581e62f8be462440d7b22c6361f7c9fa4902b upstream.

non-rcu variant of list_first_or_null_rcu

Signed-off-by: Jiri Pirko <jiri@resnulli.us>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/include/linux/list.h b/include/linux/list.h
index cc6d2aa..7690738 100644 (file)
--- a/include/linux/list.h
+++ b/include/linux/list.h
@@ -361,6 +361,17 @@ static inline void list_splice_tail_init(struct list_head *list,
 #define list_first_entry(ptr, type, member) \
        list_entry((ptr)->next, type, member)
 
 #define list_first_entry(ptr, type, member) \
        list_entry((ptr)->next, type, member)
 

+/**
+ * list_first_entry_or_null - 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 if the list is empty, it returns NULL.
+ */
+#define list_first_entry_or_null(ptr, type, member) \
+       (!list_empty(ptr) ? list_first_entry(ptr, type, member) : NULL)
+

 /**
  * list_for_each       -       iterate over a list
  * @pos:       the &struct list_head to use as a loop cursor.
 /**
  * list_for_each       -       iterate over a list
  * @pos:       the &struct list_head to use as a loop cursor.