Btrfs-progs: introduce list_{first, next}_entry/list_splice_tail{_init}

Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>

diff --git a/list.h b/list.h
index 50f4619..db7a58c 100644 (file)
--- a/list.h
+++ b/list.h
@@ -223,18 +223,18 @@ static inline int list_empty_careful(const struct list_head *head)
        return (next == head) && (next == head->prev);
 }
 
-static inline void __list_splice(struct list_head *list,
-                                struct list_head *head)
+static inline void __list_splice(const struct list_head *list,
+                                struct list_head *prev,
+                                struct list_head *next)
 {
        struct list_head *first = list->next;
        struct list_head *last = list->prev;
-       struct list_head *at = head->next;
 
-       first->prev = head;
-       head->next = first;
+       first->prev = prev;
+       prev->next = first;
 
-       last->next = at;
-       at->prev = last;
+       last->next = next;
+       next->prev = last;
 }
 
 /**
@@ -245,7 +245,19 @@ static inline void __list_splice(struct list_head *list,
 static inline void list_splice(struct list_head *list, struct list_head *head)
 {
        if (!list_empty(list))
-               __list_splice(list, head);
+               __list_splice(list, head, head->next);
+}
+
+/**
+ * list_splice_tail - join two lists, each list being a queue
+ * @list: the new list to add.
+ * @head: the place to add it in the first list.
+ */
+static inline void list_splice_tail(struct list_head *list,
+                               struct list_head *head)
+{
+       if (!list_empty(list))
+               __list_splice(list, head->prev, head);
 }
 
 /**
@@ -259,7 +271,24 @@ static inline void list_splice_init(struct list_head *list,
                                    struct list_head *head)
 {
        if (!list_empty(list)) {
-               __list_splice(list, head);
+               __list_splice(list, head, head->next);
+               INIT_LIST_HEAD(list);
+       }
+}
+
+/**
+ * list_splice_tail_init - join two lists and reinitialise the emptied list
+ * @list: the new list to add.
+ * @head: the place to add it in the first list.
+ *
+ * Each of the lists is a queue.
+ * The list at @list is reinitialised
+ */
+static inline void list_splice_tail_init(struct list_head *list,
+                                        struct list_head *head)
+{
+       if (!list_empty(list)) {
+               __list_splice(list, head->prev, head);
                INIT_LIST_HEAD(list);
        }
 }
@@ -274,6 +303,27 @@ static inline void list_splice_init(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_next_entry - get the next element from a list
+ * @ptr:       the list head to take the element from.
+ * @member:    the name of the list_struct within the struct.
+ *
+ * Note, that next is expected to be not null.
+ */
+#define list_next_entry(ptr, member) \
+       list_entry((ptr)->member.next, typeof(*ptr), 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.