Messages in this thread | | | Subject | Re: [PATCH RFC v2 02/24] scsi: allocate separate queue for reserved commands | From | John Garry <> | Date | Wed, 11 Mar 2020 07:51:18 +0000 |
| |
On 11/03/2020 06:58, Hannes Reinecke wrote: > On 3/11/20 7:22 AM, Christoph Hellwig wrote: >> On Tue, Mar 10, 2020 at 09:08:56PM +0000, John Garry wrote: >>> On 10/03/2020 18:32, Christoph Hellwig wrote: >>>> On Wed, Mar 11, 2020 at 12:25:28AM +0800, John Garry wrote: >>>>> From: Hannes Reinecke <hare@suse.com> >>>>> >>>>> Allocate a separate 'reserved_cmd_q' for sending reserved commands. >>>> >>>> Why? Reserved command specifically are not in any way tied to queues. >>>> . >>>> >>> >>> So the v1 series used a combination of the sdev queue and the per-host >>> reserved_cmd_q. Back then you questioned using the sdev queue for virtio >>> scsi, and the unconfirmed conclusion was to use a common per-host q. This is >>> the best link I can find now: >>> >>> https://www.mail-archive.com/linux-scsi@vger.kernel.org/msg83177.html >> >> That was just a question on why virtio uses the per-device tags, which >> didn't look like it made any sense. What I'm worried about here is >> mixing up the concept of reserved tags in the tagset, and queues to use >> them. Note that we already have the scsi_get_host_dev to allocate >> a scsi_device and thus a request_queue for the host itself. That seems >> like the better interface to use a tag for a host wide command vs >> introducing a parallel path. >> > Ah. Right. > Will be looking into that, and convert the patchset over to it. >
Hannes,
I assume that you will take back over this series now. Let me know. The patches are here, if not in patchwork: https://github.com/hisilicon/kernel-dev/tree/private-topic-sas-5.6-resv-commands-v2
> And the problem of the separate queue is the fact that I'll need a queue > to reserve tags from; trying to allocate a tag directly from the bitmap > turns out to be major surgery in the blocklayer with no immediate gain. > And I can't use per-device queues as for some drivers the reserved > commands are used to query the HBA itself to figure out how many devices > are present.
Right, we still need to be able to allocate somewhere apart from sdev queue
>
Thanks
| |