[ Upstream commit 78ed8cc25986ac5c21762eeddc1e86e94d422e36 ]
First example of a layer splitting the list (rather than merely taking
individual packets off it).
Involves new list.h function, list_cut_before(), like list_cut_position()
but cuts on the other side of the given entry.
Signed-off-by: Edward Cree <ecree@xxxxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
[sl: cut out non list.h bits, we only want list_cut_before]
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
include/linux/list.h | 30 ++++++++++++++++++++++++++++++
1 file changed, 30 insertions(+)
diff --git a/include/linux/list.h b/include/linux/list.h
index 5809e9a2de5b2..6f935018ea056 100644
--- a/include/linux/list.h
+++ b/include/linux/list.h
@@ -271,6 +271,36 @@ static inline void list_cut_position(struct list_head *list,
__list_cut_position(list, head, entry);
}
+/**
+ * list_cut_before - cut a list into two, before given entry
+ * @list: a new list to add all removed entries
+ * @head: a list with entries
+ * @entry: an entry within head, could be the head itself
+ *
+ * This helper moves the initial part of @head, up to but
+ * excluding @entry, from @head to @list. You should pass
+ * in @entry an element you know is on @head. @list should
+ * be an empty list or a list you do not care about losing
+ * its data.
+ * If @entry == @head, all entries on @head are moved to
+ * @list.
+ */
+static inline void list_cut_before(struct list_head *list,
+ struct list_head *head,
+ struct list_head *entry)
+{
+ if (head->next == entry) {
+ INIT_LIST_HEAD(list);
+ return;
+ }
+ list->next = head->next;
+ list->next->prev = list;
+ list->prev = entry->prev;
+ list->prev->next = list;
+ head->next = entry;
+ entry->prev = head;
+}
+
static inline void __list_splice(const struct list_head *list,
struct list_head *prev,
struct list_head *next)
--
2.20.1
