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

[Alexander Atanasov]

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 .

> 
>>               /* 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)
> 

-- 
Regards,
Alexander Atanasov