Re: [Qemu-block] [PATCH] qcow2: Release dirty entries with cache-clean-interval

[Alberto Garcia]

On Mon 06 Aug 2018 05:05:41 PM CEST, Kevin Wolf wrote:
> Am 06.08.2018 um 16:13 hat Alberto Garcia geschrieben:
>> -static inline bool can_clean_entry(Qcow2Cache *c, int i)
>> +static inline bool can_clean_entry(BlockDriverState *bs, Qcow2Cache *c, int 
>> i)
>>  {
>>      Qcow2CachedTable *t = &c->entries[i];
>> -    return t->ref == 0 && !t->dirty && t->offset != 0 &&
>> -        t->lru_counter <= c->cache_clean_lru_counter;
>> +    if (t->ref || !t->offset || t->lru_counter > 
>> c->cache_clean_lru_counter) {
>> +        return false;
>> +    }
>> +
>> +    if (qcow2_cache_entry_flush(bs, c, i) < 0) {
>> +        return false;
>> +    }
>
> We're not in coroutine context here, so qcow2_cache_entry_flush() will
> be blocking. I don't think that's acceptable in a timer callback.
>
> On the other hand, if we made it non-blocking by moving it into a
> coroutine that could yield, we would have to consider races with other
> parts of the code and at least take s->lock and implement
> .bdrv_co_drain_begin/end callbacks.

Oh, I see... it's probably not worth complicating the code for this then.

Berto