[PATCH 1/6] io-wq: add helper to merge two wq_lists

[Hao Xu <haoxu@linux.alibaba.com>]

add a helper to merge two wq_lists, it will be useful in the next
patches.

Reviewed-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Hao Xu <haoxu@linux.alibaba.com>
---
 fs/io-wq.h | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/fs/io-wq.h b/fs/io-wq.h
index 41bf37674a49..3709b7c5ec98 100644
--- a/fs/io-wq.h
+++ b/fs/io-wq.h
@@ -52,6 +52,28 @@ static inline void wq_list_add_after(struct io_wq_work_node *node,
 		list->last = node;
 }
 
+/**
+ * wq_list_merge - merge the second list to the first one.
+ * @list0: the first list
+ * @list1: the second list
+ * Return the first node after mergence.
+ */
+static inline struct io_wq_work_node *wq_list_merge(struct io_wq_work_list *list0,
+						    struct io_wq_work_list *list1)
+{
+	struct io_wq_work_node *ret;
+
+	if (!list0->first) {
+		ret = list1->first;
+	} else {
+		ret = list0->first;
+		list0->last->next = list1->first;
+	}
+	INIT_WQ_LIST(list0);
+	INIT_WQ_LIST(list1);
+	return ret;
+}
+
 static inline void wq_list_add_tail(struct io_wq_work_node *node,
 				    struct io_wq_work_list *list)
 {
-- 
2.24.4