llist: llist_add() can use llist_add_batch()

llist_add(new, head) can simply use llist_add_batch(new, new, head),
no need to duplicate the code.

This obviously uninlines llist_add() and to me this is a win. But we
can make llist_add_batch() inline if this is desirable, in this case
gcc can notice that new_first == new_last if the caller is llist_add().

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Andrey Vagin <avagin@openvz.org>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

include/linux/llist.h

@@ -142,6 +142,9 @@ static inline struct llist_node *llist_next(struct llist_node *node)
 	return node->next;
 }
 
+extern bool llist_add_batch(struct llist_node *new_first,
+			    struct llist_node *new_last,
+			    struct llist_head *head);
 /**
  * llist_add - add a new entry
  * @new:	new entry to be added
@@ -151,13 +154,7 @@ static inline struct llist_node *llist_next(struct llist_node *node)
  */
 static inline bool llist_add(struct llist_node *new, struct llist_head *head)
 {
-	struct llist_node *first;
-
-	do {
-		new->next = first = ACCESS_ONCE(head->first);
-	} while (cmpxchg(&head->first, first, new) != first);
-
-	return !first;
+	return llist_add_batch(new, new, head);
 }
 
 /**
@@ -173,9 +170,6 @@ static inline struct llist_node *llist_del_all(struct llist_head *head)
 	return xchg(&head->first, NULL);
 }
 
-extern bool llist_add_batch(struct llist_node *new_first,
-			    struct llist_node *new_last,
-			    struct llist_head *head);
 extern struct llist_node *llist_del_first(struct llist_head *head);
 
 #endif /* LLIST_H */