[Devel] [RFC PATCH vz9 v6 07/62] dm-ploop: convert wait_list and wb_batch_llist to use lockless lists

[Pavel Tikhomirov]

On 12/6/24 05:55, Alexander Atanasov wrote:
> @@ -1758,22 +1767,18 @@ static void ploop_process_resubmit_pios(struct ploop *ploop,
>   static void ploop_submit_metadata_writeback(struct ploop *ploop)
>   {
>   	struct md_page *md;
> -	while (1) {
> -		write_lock_irq(&ploop->bat_rwlock);
> -		md = list_first_entry_or_null(&ploop->wb_batch_list,
> -				struct md_page, wb_link);
> -		if (!md) {
> -			write_unlock_irq(&ploop->bat_rwlock);
> -			break;
> -		}
> -		list_del_init(&md->wb_link);
> -		/* L1L2 mustn't be redirtyed, when wb in-flight! */
> +	struct md_page *t;
> +	struct llist_node *wbl;
> +
> +	wbl = llist_del_all(&ploop->wb_batch_llist);
> +	if (!wbl)
> +		return;
> +	wbl = llist_reverse_order(wbl);
> +	llist_for_each_entry_safe(md, t, wbl, wb_llink) {

Why do we need _safe version here? Noone can delete from wbl at this point.

>   		WARN_ON_ONCE(!test_bit(MD_DIRTY, &md->status));
>   		WARN_ON_ONCE(test_bit(MD_WRITEBACK, &md->status));
>   		set_bit(MD_WRITEBACK, &md->status);
>   		clear_bit(MD_DIRTY, &md->status);
> -		write_unlock_irq(&ploop->bat_rwlock);
> -
>   		ploop_index_wb_submit(ploop, md->piwb);
>   	}
>   }

-- 
Best regards, Tikhomirov Pavel
Senior Software Developer, Virtuozzo.