于 2016/4/27 23:21, Jens Axboe 写道:
> On 04/27/2016 06:06 AM, xiakaixu wrote:
>>> +void __wbt_done(struct rq_wb *rwb)
>>> +{
>>> + int inflight, limit = rwb->wb_normal;
>>> +
>>> + /*
>>> + * If the device does write back caching, drop further down
>>> + * before we wake people up.
>>> + */
>>> + if (rwb->wc && !atomic_read(&rwb->bdi->wb.dirty_sleeping))
>>> + limit = 0;
>>> + else
>>> + limit = rwb->wb_normal;
>>> +
>>> + /*
>>> + * Don't wake anyone up if we are above the normal limit. If
>>> + * throttling got disabled (limit == 0) with waiters, ensure
>>> + * that we wake them up.
>>> + */
>>> + inflight = atomic_dec_return(&rwb->inflight);
>>> + if (limit && inflight >= limit) {
>>> + if (!rwb->wb_max)
>>> + wake_up_all(&rwb->wait);
>>> + return;
>>> + }
>>> +
>> Hi Jens,
>>
>> Just a little confused about this. The rwb->wb_max can't be 0 if the variable
>> 'limit' does not equal to 0. So the if (!rwb->wb_max) branch maybe does not
>> make sense.
>
> You are right, it doesn't make a lot of sense. I think it suffers from code shuffling. How about the attached? The important part is that we wake up waiters, if wbt got disabled while we had tracked IO in flight.
>
Hi Jens,
The modified patch in another mail looks better. Maybe there are still
some places coube be improved. You can find them in that mail.
--
Regards
Kaixu Xia
--
To unsubscribe from this list: send the line "unsubscribe linux-block" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
