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

[Pavel Tikhomirov]

On 1/20/25 18:51, Alexander Atanasov wrote:
> On 20.01.25 11:43, Pavel Tikhomirov wrote:
>>
>>
>> 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;
>>> +
>>> +    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)) {
>>
>> Why do we add "!llist_empty(&md->wait_llist)" condition here? If it's 
>> intentional, it should probably be explained and be a separate patch, 
>> because it seems unrelated to what the commit message says.
> 
> 
> It is intentional - If we have pios in &md->wait_llist we can not delay 
> since it will delay pio execution. Updated commit message .

It should definitely be a separate patch, as it's unrelated to adding 
return value to ploop_submit_metadata_writeback.

> 
>>
>>>               /* 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.