Re: [PATCH RFC v7 12/12] hpsa: enable host_tagset and switch to MQ

John Garry
2020-07-14T10:37:04Z

On 14/07/2020 11:19, Hannes Reinecke wrote:
> Correct. There is only one tagset per host, even if the host supports
> several queues (guess why it's called smart PQI:-).
> And mainline code isn't really wrong, it just allocates the next free
> tag from the host tagset; it's not using the block-layer tags at all.
> Precisely because the block layer currently cannot guarantee that tags
> are unique per host.

ok, but it's not exemplary in what it does. And I suppose that's why it
needs to spin indefinitely for a free tag in pqi_alloc_io_request(),
instead of failing immediately when none are free.

>
> And the point of this patchset is exactly that the block layer will only
> send up to 'can_queue' requests, irrespective on how many hardware
> queues are present.
>
> But anyway, I'll test it on smartpqi, too.
>

Great, thanks.