[PATCH v2 1/2] blk-mq: add tagset quiesce interface

[Christoph Hellwig]

On Tue, Oct 18, 2022 at 12:06:41PM +0300, Sagi Grimberg wrote:
>>   +	/*
>> +	 * Mark the disk dead to prevent new opens, and set the capacity to 0
>> +	 * to end buffered writers dirtying pages that can't be synced.
>> +	 */
>>   	blk_mark_disk_dead(ns->disk);
>> -	nvme_start_ns_queue(ns);
>> -
>>   	set_capacity_and_notify(ns->disk, 0);
>> +
>> +	/* forcibly unquiesce queues to avoid blocking dispatch */
>> +	nvme_start_ns_queue(ns);
>>   }
>
> If we no longer have this ordering requirement, then I don't see why
> the unquiesce cannot move before or after nvme_set_queue_dying and apply
> a tagset-wide quiesce/unquiesce...

Yes.  After this patch we can simply do the tagset-wide unquiesce
after the loop calling blk_mark_disk_dead and set_capacity_and_notify.

We can then also move the NЅ_DEAD flag to the controller..