[Devel] [PATCH vz9 v1 06/63] dm-ploop: convert enospc handling to use lockless lists

[Alexander Atanasov]

On 3.02.25 8:01, Pavel Tikhomirov wrote:
> 
>> @@ -166,7 +171,6 @@ static bool ploop_try_delay_enospc(struct ploop_rq 
>> *prq, struct pio *pio)
>>       bool delayed = true;
>>       unsigned long flags;
>> -    spin_lock_irqsave(&ploop->deferred_lock, flags);
>>       if (unlikely(ploop->wants_suspend)) {
>>           delayed = false;
>>           goto unlock;
>> @@ -176,10 +180,11 @@ static bool ploop_try_delay_enospc(struct 
>> ploop_rq *prq, struct pio *pio)
>>       pr_err_once(PL_FMT("underlying disk is almost full"),
>>           ploop_device_name(ploop));
>> +    spin_lock_irqsave(&ploop->deferred_lock, flags);
>>       ploop->event_enospc = true;
>> -    list_add_tail(&pio->list, &ploop->enospc_pios);
>> -unlock:
>>       spin_unlock_irqrestore(&ploop->deferred_lock, flags);
>> +    llist_add((struct llist_node *)(&pio->list), &ploop->enospc_pios);
>> +unlock:
>>       if (delayed)
>>           mod_timer(&ploop->enospc_timer, jiffies + 
>> PLOOP_ENOSPC_TIMEOUT);
> 
> Can you please explain why we need to take defered_lock around 
> ploop->event_enospc setting after your patch? (It looks that this lock 
> does not do anything now.)
> 

see static int ploop_get_event(...), without lock event can be missed

-- 
Regards,
Alexander Atanasov