[Devel] [RFC PATCH vz9 v6 39/62] dm-ploop: prepare bat updates under bat_lock

[Pavel Tikhomirov]

Here is possible scenario of double-unlock of bat_lock:

On 12/6/24 05:56, Alexander Atanasov wrote:
> @@ -1758,23 +1789,29 @@ static void ploop_process_one_discard_pio(struct ploop *ploop, struct pio *pio)
>   	struct ploop_index_wb *piwb;
>   	struct md_page *md;
>   	map_index_t *to;
> +	unsigned long flags;
>   
>   	WARN_ON(ploop->nr_deltas != 1 ||
>   		pio->queue_list_id != PLOOP_LIST_DISCARD);
>   
>   	page_id = ploop_bat_clu_to_page_nr(clu);
>   	md = ploop_md_page_find(ploop, page_id);
> -	if (ploop_delay_if_md_busy(ploop, md, PIWB_TYPE_DISCARD, pio))

take bat_lock:

> +	spin_lock_irqsave(&ploop->bat_lock, flags);
> +	if (ploop_delay_if_md_busy(ploop, md, PIWB_TYPE_DISCARD, pio)) {
> +		spin_unlock_irqrestore(&ploop->bat_lock, flags);
>   		goto out;
> +	}
> +
>   
>   	if (!test_bit(MD_DIRTY, &md->status)) {
> -		 /* Unlocked since MD_DIRTY is set and cleared from this work */
>   		if (ploop_prepare_bat_update(ploop, md, PIWB_TYPE_DISCARD) < 0) {
>   			pio->bi_status = BLK_STS_RESOURCE;
>   			goto err;
>   		}
>   		bat_update_prepared = true;
> +		ploop_md_make_dirty(ploop, md);
>   	}

release bat_lock:

> +	spin_unlock_irqrestore(&ploop->bat_lock, flags);
>   
>   	piwb = md->piwb;
>   
> @@ -1784,18 +1821,20 @@ static void ploop_process_one_discard_pio(struct ploop *ploop, struct pio *pio)
>   	to = piwb->kmpage;
>   	if (WARN_ON_ONCE(!to[clu])) {
>   		pio->bi_status = BLK_STS_IOERR;
> +		clear_bit(MD_DIRTY, &md->status);

goto err:

>   		goto err;
>   	} else {
>   		WRITE_ONCE(to[clu], 0);
> +		spin_lock_irqsave(&piwb->lock, flags);
>   		list_add_tail(&pio->list, &piwb->ready_data_pios);
> +		spin_unlock_irqrestore(&piwb->lock, flags);
>   	}
>   
> -	if (bat_update_prepared)
> -		ploop_md_make_dirty(ploop, md);
>   	ploop_md_up_prio(ploop, md);
>   out:
>   	return;
>   err:

release bat lock again:

> +	spin_unlock_irqrestore(&ploop->bat_lock, flags);
>   	if (bat_update_prepared)
>   		ploop_break_bat_update(ploop, md);
>   	ploop_pio_endio(pio);

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