io-wq: add helper to merge two wq_lists

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>
Link: https://lore.kernel.org/r/20211207093951.247840-2-haoxu@linux.alibaba.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/fs/io-wq.h b/fs/io-wq.h
index 41bf376..3709b7c 100644 (file)
--- 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)
 {