[PATCH -mm 1/5] list.h: add list_singleton

[Masami Hiramatsu <mhiramat@redhat.com>]

Add list_singleton to check a list has just one entry.

list_singleton is useful to check whether a list_head which
have been temporarily allocated for listing objects can be
released or not.

Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
---
 include/linux/list.h |    9 +++++++++
 1 file changed, 9 insertions(+)

Index: 2.6.25-rc5-mm1/include/linux/list.h
===================================================================
--- 2.6.25-rc5-mm1.orig/include/linux/list.h
+++ 2.6.25-rc5-mm1/include/linux/list.h
@@ -211,6 +211,15 @@ static inline int list_empty_careful(con
 	return (next == head) && (next == head->prev);
 }

+/**
+ * list_singleton - tests whether a list has just one entry.
+ * @head: the list to test.
+ */
+static inline int list_singleton(const struct list_head *head)
+{
+	return !list_empty(head) && (head->next == head->prev);
+}
+
 static inline void __list_splice(struct list_head *list,
 				 struct list_head *head)
 {
-- 
Masami Hiramatsu

Software Engineer
Hitachi Computer Products (America) Inc.
Software Solutions Division

e-mail: mhiramat@redhat.com