Re: [PATCH 2/6] nvme-pci: fix the freeze and quiesce for shutdown and reset case

[jianchao.wang]

Hi Keith

Thanks for your kindly response.

On 02/03/2018 02:24 AM, Keith Busch wrote:
> On Fri, Feb 02, 2018 at 03:00:45PM +0800, Jianchao Wang wrote:
>> Currently, request queue will be frozen and quiesced for both reset
>> and shutdown case. This will trigger ioq requests in RECONNECTING
>> state which should be avoided to prepare for following patch.
>> Just freeze request queue for shutdown case and drain all the resudual
>> entered requests after controller has been shutdown.

> Freezing is not just for shutdown. It's also used so
> blk_mq_update_nr_hw_queues will work if the queue count changes across
> resets.
blk_mq_update_nr_hw_queues will freeze the queue itself. Please refer to.
static void __blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set,
                                                        int nr_hw_queues)
{
        struct request_queue *q;

        lockdep_assert_held(&set->tag_list_lock);

        if (nr_hw_queues > nr_cpu_ids)
                nr_hw_queues = nr_cpu_ids;
        if (nr_hw_queues < 1 || nr_hw_queues == set->nr_hw_queues)
                return;

        list_for_each_entry(q, &set->tag_list, tag_set_list)
                blk_mq_freeze_queue(q);

        set->nr_hw_queues = nr_hw_queues;
        blk_mq_update_queue_map(set);
        list_for_each_entry(q, &set->tag_list, tag_set_list) {
                blk_mq_realloc_hw_ctxs(set, q);
                blk_mq_queue_reinit(q);
        }

        list_for_each_entry(q, &set->tag_list, tag_set_list)
                blk_mq_unfreeze_queue(q);
}

Thanks
Jianchao