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

[Pavel Begunkov <asml.silence@gmail.com>]

On 10/29/21 13:22, Hao Xu wrote:
> add a helper to merge two wq_lists, it will be useful in the next
> patches.
> 
> Signed-off-by: Hao Xu <haoxu@linux.alibaba.com>
> ---
>   fs/io-wq.h | 21 +++++++++++++++++++++
>   1 file changed, 21 insertions(+)
> 
> diff --git a/fs/io-wq.h b/fs/io-wq.h
> index 41bf37674a49..a7b0b505db9d 100644
> --- a/fs/io-wq.h
> +++ b/fs/io-wq.h
> @@ -52,6 +52,27 @@ 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 list0 if list1 is NULL, and vice versa.
> + * Otherwise after merge, list0 contains the merged list.
> + */
> +static inline struct io_wq_work_list *wq_list_merge(struct io_wq_work_list *list0,
> +						    struct io_wq_work_list *list1)

might be easier if it'd be a splice or even initialising both lists
and returning a node ptr. E.g. (untested)

struct node* wq_list_splice(list0, list1) {
	struct node *ret;

	if (!list0->first) {
		ret = list1->first;
	} else {
		ret = list0->first;
		list0->last->next = list1->first;
	}

	init(list0);
	init(list1);
	return ret;
}

> +{
> +	if (!list1 || !list1->first)

Can also get rid of NULL checks, i.e. !list1

> +		return list0;
> +
> +	if (!list0 || !list0->first)
> +		return list1;
> +
> +	list0->last->next = list1->first;
> +	list0->last = list1->last;
> +	return list0;
> +}
> +
>   static inline void wq_list_add_tail(struct io_wq_work_node *node,
>   				    struct io_wq_work_list *list)
>   {
> 

-- 
Pavel Begunkov