Re: [PATCH 10/18] scsi: implement reserved command handling

John Garry
2021-05-04T10:55:24Z

On 04/05/2021 07:17, Hannes Reinecke wrote:
> On 5/4/21 5:20 AM, Bart Van Assche wrote:
>> On 5/3/21 8:03 AM, Hannes Reinecke wrote:
>>> These commands are set aside before allocating the block-mq tag bitmap,
>>> so they'll never show up as busy in the tag map.
>>
>> That doesn't sound correct to me. Should the above perhaps be changed
>> into "blk_mq_start_request() is never called for internal commands so
>> they'll never show up as busy in the tag map"?
>>
> Yes, will do.

So why don't these - or shouldn't these - turn up in the busy tag map?

One of the motivations to use these block requests for internal commands
is that we can take advantage of the block layer handling for CPU
hotplug for MQ hosts, i.e. if blk-mq can't see these are inflight, then
they would be missed in blk_mq_hctx_notify_offline() ->
blk_mq_hctx_has_requests(), right? And who knows what else...

Thanks,
John