On 12/6/22 17:06, Paolo Valente wrote:
>
>
>> Il giorno 21 nov 2022, alle ore 02:01, Damien Le Moal <damien.lemoal@xxxxxxxxxxxxxxxxxx> ha scritto:
>>
>
> ...
>
>>
>>> }
>>>
>>> static bool bfq_bio_merge(struct request_queue *q, struct bio *bio,
>>> @@ -7144,6 +7159,8 @@ static int bfq_init_queue(struct request_queue *q, struct elevator_type *e)
>>> {
>>> struct bfq_data *bfqd;
>>> struct elevator_queue *eq;
>>> + unsigned int i;
>>> + struct blk_independent_access_ranges *ia_ranges = q->disk->ia_ranges;
>>>
>>> eq = elevator_alloc(q, e);
>>> if (!eq)
>>> @@ -7187,10 +7204,31 @@ static int bfq_init_queue(struct request_queue *q, struct elevator_type *e)
>>> bfqd->queue = q;
>>>
>>> /*
>>> - * Multi-actuator support not complete yet, default to single
>>> - * actuator for the moment.
>>> + * If the disk supports multiple actuators, we copy the independent
>>> + * access ranges from the request queue structure.
>>> */
>>> - bfqd->num_actuators = 1;
>>> + spin_lock_irq(&q->queue_lock);
>>> + if (ia_ranges) {
>>> + /*
>>> + * Check if the disk ia_ranges size exceeds the current bfq
>>> + * actuator limit.
>>> + */
>>> + if (ia_ranges->nr_ia_ranges > BFQ_MAX_ACTUATORS) {
>>> + pr_crit("nr_ia_ranges higher than act limit: iars=%d, max=%d.\n",
>>> + ia_ranges->nr_ia_ranges, BFQ_MAX_ACTUATORS);
>>> + pr_crit("Falling back to single actuator mode.\n");
>>> + bfqd->num_actuators = 0;
>>> + } else {
>>> + bfqd->num_actuators = ia_ranges->nr_ia_ranges;
>>> +
>>> + for (i = 0; i < bfqd->num_actuators; i++)
>>> + bfqd->ia_ranges[i] = ia_ranges->ia_range[i];
>>> + }
>>> + } else {
>>> + bfqd->num_actuators = 0;
>>
>> That is very weird. The default should be 1 actuator.
>> ia_ranges->nr_ia_ranges is 0 when the disk does not provide any range
>> information, meaning it is a regular disk with a single actuator.
>
> Actually, IIUC this assignment to 0 seems to be done exactly when you
> say that it should be done, i.e., when the disk does not provide any
> range information (ia_ranges is NULL). Am I missing something else?
No ranges reported means no extra actuators, so a single actuator an
single LBA range for the entire device. In that case, bfq should process
all IOs using bfqd->ia_ranges[0]. The get range function will always
return that range. That makes the code clean and avoids different path for
nr_ranges == 1 and nr_ranges > 1. No ?
>
> Once again, all other suggestions applied. I'm about to submit a V7.
>
> Thanks,
> Paolo
>
--
Damien Le Moal
Western Digital Research
