[ 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@solarflare.com Signed-off-by: David S. Miller davem@davemloft.net [sl: cut out non list.h bits, we only want list_cut_before] Signed-off-by: Sasha Levin sashal@kernel.org --- 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)