From: John Garry <john.garry@huawei.com>
To: Hannes Reinecke <hare@suse.de>, Christoph Hellwig <hch@infradead.org>
Cc: <axboe@kernel.dk>, <jejb@linux.ibm.com>,
<martin.petersen@oracle.com>, <ming.lei@redhat.com>,
<bvanassche@acm.org>, <linux-block@vger.kernel.org>,
<linux-kernel@vger.kernel.org>, <linux-scsi@vger.kernel.org>,
<virtualization@lists.linux-foundation.org>,
<esc.storagedev@microsemi.com>, <chenxiang66@hisilicon.com>,
Hannes Reinecke <hare@suse.com>
Subject: Re: [PATCH RFC v2 02/24] scsi: allocate separate queue for reserved commands
Date: Wed, 11 Mar 2020 07:51:18 +0000 [thread overview]
Message-ID: <f9cd5ffc-4246-3815-d6ab-9d4f7535bcb8@huawei.com> (raw)
In-Reply-To: <7bc94a9f-ec86-b343-0951-eba548c71b67@suse.de>
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
next prev parent reply other threads:[~2020-03-11 7:51 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-10 16:25 [PATCH RFC v2 00/24] scsi: enable reserved commands for LLDDs John Garry
2020-03-10 16:25 ` [PATCH RFC v2 01/24] scsi: add 'nr_reserved_cmds' field to the SCSI host template John Garry
2020-03-10 23:08 ` Ming Lei
2020-03-11 6:55 ` Hannes Reinecke
2020-03-11 8:00 ` Ming Lei
2020-03-10 16:25 ` [PATCH RFC v2 02/24] scsi: allocate separate queue for reserved commands John Garry
2020-03-10 18:32 ` Christoph Hellwig
2020-03-10 21:08 ` John Garry
2020-03-11 6:22 ` Christoph Hellwig
2020-03-11 6:58 ` Hannes Reinecke
2020-03-11 7:51 ` John Garry [this message]
2020-04-06 9:05 ` Hannes Reinecke
2020-04-07 11:54 ` John Garry
2020-04-07 14:00 ` Hannes Reinecke
2020-04-07 14:35 ` John Garry
2020-04-07 14:45 ` Hannes Reinecke
2020-04-07 15:19 ` John Garry
2020-04-07 16:30 ` Christoph Hellwig
2020-04-23 14:13 ` John Garry
2020-04-23 14:49 ` Hannes Reinecke
2020-04-23 15:33 ` John Garry
2020-03-10 16:25 ` [PATCH RFC v2 03/24] blk-mq: Implement blk_mq_rq_is_reserved() John Garry
2020-03-10 16:25 ` [PATCH RFC v2 04/24] scsi: Add scsi_{get, put}_reserved_cmd() John Garry
2020-03-10 16:25 ` [PATCH RFC v2 05/24] csiostor: use reserved command for LUN reset John Garry
2020-03-10 16:25 ` [PATCH RFC v2 06/24] scsi: add scsi_cmd_from_priv() John Garry
2020-03-10 16:25 ` [PATCH RFC v2 07/24] virtio_scsi: use reserved commands for TMF John Garry
2020-03-10 16:25 ` [PATCH RFC v2 08/24] scsi: add host tagset busy iterator John Garry
2020-03-10 16:25 ` [PATCH RFC v2 09/24] fnic: use reserved commands John Garry
2020-03-10 16:25 ` [PATCH RFC v2 10/24] fnic: use scsi_host_tagset_busy_iter() to traverse commands John Garry
2020-03-10 16:25 ` [PATCH RFC v2 11/24] hpsa: move hpsa_hba_inquiry after scsi_add_host() John Garry
2020-03-10 16:25 ` [PATCH RFC v2 12/24] hpsa: use reserved commands John Garry
2020-03-11 8:10 ` Ming Lei
2020-03-17 9:38 ` John Garry
2020-03-17 9:48 ` Hannes Reinecke
2020-03-30 13:42 ` John Garry
2020-03-10 16:25 ` [PATCH RFC v2 13/24] hpsa: use blk_mq_tagset_busy_iter() to traverse outstanding commands John Garry
2020-03-10 16:25 ` [PATCH RFC v2 14/24] hpsa: drop refcount field from CommandList John Garry
2020-03-10 16:25 ` [PATCH RFC v2 15/24] snic: use reserved commands John Garry
2020-03-10 16:25 ` [PATCH RFC v2 16/24] snic: use tagset iter for traversing commands John Garry
2020-03-10 16:25 ` [PATCH RFC v2 17/24] aacraid: move scsi_add_host() John Garry
2020-03-10 16:25 ` [PATCH RFC v2 18/24] aacraid: use private commands John Garry
2020-03-10 16:25 ` [PATCH RFC v2 19/24] aacraid: replace cmd_list with scsi_host_tagset_busy_iter() John Garry
2020-03-10 16:25 ` [PATCH RFC v2 20/24] aacraid: use scsi_host_tagset_busy_iter() to traverse outstanding commands John Garry
2020-03-10 16:25 ` [PATCH RFC v2 21/24] dpt_i2o: drop cmd_list usage John Garry
2020-03-10 16:25 ` [PATCH RFC v2 22/24] scsi: drop scsi command list John Garry
2020-03-10 18:35 ` Christoph Hellwig
2020-03-10 20:47 ` John Garry
2020-03-10 16:25 ` [PATCH RFC v2 23/24] scsi: libsas: aic94xx: hisi_sas: mvsas: pm8001: Allocate Scsi_cmd for slow task John Garry
2020-03-10 16:25 ` [PATCH RFC v2 24/24] scsi: hisi_sas: Use libsas slow task SCSI command John Garry
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