[Devel] [RFC PATCH vz9 v6 43/62] dm-ploop: make ploop_submit_metadata_writeback return number of requests sent

[Pavel Tikhomirov]

On 12/6/24 05:56, Alexander Atanasov wrote:
> We need to wait for write back to complete to issue pending flushes.
> To know if we have to wait return numer of pios submitted.
> 
> https://virtuozzo.atlassian.net/browse/VSTOR-91821
> Signed-off-by: Alexander Atanasov <alexander.atanasov at virtuozzo.com>
> ---
>   drivers/md/dm-ploop-map.c | 15 ++++++++++++---
>   1 file changed, 12 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/md/dm-ploop-map.c b/drivers/md/dm-ploop-map.c
> index 276e8cf3b178..b3e8b934ff13 100644
> --- a/drivers/md/dm-ploop-map.c
> +++ b/drivers/md/dm-ploop-map.c
> @@ -1889,7 +1889,7 @@ static inline int ploop_runners_have_pending(struct ploop *ploop)
>   }
>   #endif
>   
> -static void ploop_submit_metadata_writeback(struct ploop *ploop, int force)
> +static int ploop_submit_metadata_writeback(struct ploop *ploop, int force)
>   {
>   	unsigned long flags;
>   	LIST_HEAD(ll_skipped);
> @@ -1897,19 +1897,25 @@ static void ploop_submit_metadata_writeback(struct ploop *ploop, int force)
>   	struct llist_node *pos, *t;
>   	struct llist_node *ll_wb_batch;
>   	unsigned long timeout = jiffies;
> +	int ret;
>   
>   	/* Lock here to protect against md_inflight counting */
>   	spin_lock_irqsave(&ploop->bat_lock, flags);
>   	ll_wb_batch = llist_del_all(&ploop->wb_batch_llist);
>   	spin_unlock_irqrestore(&ploop->bat_lock, flags);
> +	if (!ll_wb_batch)
> +		return 0;

This looks excess as llist_for_each_safe below will not do anything on 
empty list.

> +
> +	ret = 0;
> +
>   	/*
>   	 * Pages are set dirty so no one must touch lists
>   	 * if new md entries are dirtied they are added at the start of the list
>   	 */
>   	llist_for_each_safe(pos, t, ll_wb_batch) {
>   		md = list_entry((struct list_head *)pos, typeof(*md), wb_link);
> -		if (test_bit(MD_HIGHPRIO, &md->status) || time_before(md->dirty_timeout, timeout)
> -		    || ploop->force_md_writeback) {
> +		if (!llist_empty(&md->wait_llist) || force || test_bit(MD_HIGHPRIO, &md->status) ||
> +			time_before(md->dirty_timeout, timeout)) {
>   			/* L1L2 mustn't be redirtyed, when wb in-flight! */
>   			WARN_ON_ONCE(!test_bit(MD_DIRTY, &md->status));
>   			WARN_ON_ONCE(test_bit(MD_WRITEBACK, &md->status));
> @@ -1917,10 +1923,13 @@ static void ploop_submit_metadata_writeback(struct ploop *ploop, int force)
>   			clear_bit(MD_DIRTY, &md->status);
>   			clear_bit(MD_HIGHPRIO, &md->status);
>   			ploop_index_wb_submit(ploop, md->piwb);
> +			ret++;
>   		} else {
> +			INIT_LIST_HEAD(&md->wb_link);
>   			llist_add((struct llist_node *)&md->wb_link, &ploop->wb_batch_llist);
>   		}
>   	}
> +	return ret;
>   }
>   
>   static void process_ploop_fsync_work(struct ploop *ploop, struct llist_node *llflush_pios)

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