From: Hannes Reinecke <hare@suse.de>
To: Christoph Hellwig <hch@lst.de>
Cc: Damien Le Moal <damien.lemoal@opensource.wdc.com>,
John Garry <john.garry@huawei.com>,
axboe@kernel.dk, jejb@linux.ibm.com, martin.petersen@oracle.com,
brking@us.ibm.com, linux-block@vger.kernel.org,
linux-ide@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-scsi@vger.kernel.org, chenxiang66@hisilicon.com
Subject: Re: [PATCH RFC v2 03/18] scsi: core: Implement reserved command handling
Date: Mon, 20 Jun 2022 09:03:47 +0200 [thread overview]
Message-ID: <2ea41701-8be5-f981-d178-0d8e703962e0@suse.de> (raw)
In-Reply-To: <20220620062828.GA10753@lst.de>
On 6/20/22 08:28, Christoph Hellwig wrote:
> On Mon, Jun 20, 2022 at 08:24:24AM +0200, Hannes Reinecke wrote:
>> So my idea for SATA is simply _not_ to use reserved tags.
>> Any TMF functions (or the equivalent thereof) should always be sent as
>> non-NCQ commands. And when doing so we're back to QD=1 on SATA anyway, so
>> there _must_ be tags available. Consequently the main reason for having
>> reserved tags (namely to guarantee that tags are available for TMF) doesn't
>> apply here.
>
> At least in the non-elevator case (which includes all passthrough I/O)
> request have tags assigned as soon as they are allocated. So, we
> absolutely can have all tags allocated and then need to do a TMF.
SATA internals may come to the rescue here; if there's an error all NCQ
commands are aborted. So we'll get at least one command tag back.
As for the command duration limits I'm still waiting for clarification
from Damien if we can reuse tags there.
But I do agree it's ugly.
Cheers,
Hannes
--
Dr. Hannes Reinecke Kernel Storage Architect
hare@suse.de +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Ivo Totev, Andrew
Myers, Andrew McDonald, Martje Boudien Moerman
next prev parent reply other threads:[~2022-06-20 7:03 UTC|newest]
Thread overview: 60+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-06-09 10:29 [PATCH RFC v2 00/18] blk-mq/libata/scsi: SCSI driver tagging improvements John Garry
2022-06-09 10:29 ` [PATCH RFC v2 01/18] blk-mq: Add a flag for reserved requests John Garry
2022-06-14 6:43 ` Christoph Hellwig
2022-06-14 9:29 ` John Garry
2022-06-14 18:00 ` Bart Van Assche
2022-06-14 18:30 ` John Garry
2022-06-09 10:29 ` [PATCH RFC v2 02/18] scsi: core: Resurrect scsi_{get,free}_host_dev() John Garry
2022-06-14 6:44 ` Christoph Hellwig
2022-06-14 9:33 ` John Garry
2022-06-14 19:33 ` Bart Van Assche
2022-06-15 13:44 ` John Garry
2022-06-09 10:29 ` [PATCH RFC v2 03/18] scsi: core: Implement reserved command handling John Garry
2022-06-13 7:01 ` Damien Le Moal
2022-06-13 8:25 ` John Garry
2022-06-13 9:06 ` Damien Le Moal
2022-06-13 9:34 ` John Garry
2022-06-13 9:43 ` Damien Le Moal
2022-06-13 10:05 ` John Garry
2022-06-20 6:45 ` Hannes Reinecke
2022-06-20 7:06 ` Damien Le Moal
2022-06-14 18:20 ` Bart Van Assche
2022-06-14 23:43 ` Damien Le Moal
2022-06-15 7:35 ` John Garry
2022-06-16 2:47 ` Damien Le Moal
2022-06-16 8:24 ` John Garry
2022-06-16 8:41 ` Damien Le Moal
2022-06-20 8:27 ` Hannes Reinecke
2022-06-20 9:02 ` Damien Le Moal
2022-06-20 9:05 ` Christoph Hellwig
2022-06-20 11:24 ` Damien Le Moal
2022-06-20 11:56 ` Hannes Reinecke
2022-06-20 8:02 ` Hannes Reinecke
2022-06-20 6:24 ` Hannes Reinecke
2022-06-20 6:28 ` Christoph Hellwig
2022-06-20 7:03 ` Hannes Reinecke [this message]
2022-06-20 7:14 ` Damien Le Moal
2022-06-09 10:29 ` [PATCH RFC v2 04/18] scsi: core: Add support to send reserved commands John Garry
2022-06-13 7:03 ` Damien Le Moal
2022-06-13 9:40 ` John Garry
2022-06-13 9:41 ` Damien Le Moal
2022-06-09 10:29 ` [PATCH RFC v2 05/18] scsi: core: Allocate SCSI host sdev when required John Garry
2022-06-09 10:29 ` [PATCH RFC v2 06/18] libata-scsi: Add ata_scsi_queue_internal() John Garry
2022-06-13 7:12 ` Damien Le Moal
2022-06-13 9:41 ` John Garry
2022-06-09 10:29 ` [PATCH RFC v2 07/18] libata-scsi: Add ata_internal_queuecommand() John Garry
2022-06-13 7:16 ` Damien Le Moal
2022-06-13 9:44 ` John Garry
2022-06-09 10:29 ` [PATCH RFC v2 08/18] libata: Queue ATA internal commands as requests John Garry
2022-06-13 7:22 ` Damien Le Moal
2022-06-13 8:13 ` John Garry
2022-06-09 10:29 ` [PATCH RFC v2 09/18] scsi: ipr: Support reserved commands John Garry
2022-06-09 10:29 ` [PATCH RFC v2 10/18] libata/scsi: libsas: Add sas_queuecommand_internal() John Garry
2022-06-09 10:29 ` [PATCH RFC v2 11/18] scsi: libsas: Don't attempt to find scsi host rphy in slave alloc John Garry
2022-06-09 10:29 ` [PATCH RFC v2 12/18] scsi: libsas drivers: Prepare for reserved commands John Garry
2022-06-09 10:29 ` [PATCH RFC v2 13/18] scsi: libsas: Allocate SCSI commands for tasks John Garry
2022-06-09 10:29 ` [PATCH RFC v2 14/18] scsi: libsas: Queue SMP commands as requests John Garry
2022-06-09 10:29 ` [PATCH RFC v2 15/18] scsi: libsas: Queue TMF " John Garry
2022-06-09 10:29 ` [PATCH RFC v2 16/18] scsi: core: Add scsi_alloc_request_hwq() John Garry
2022-06-09 10:29 ` [PATCH RFC v2 17/18] scsi: libsas: Queue internal abort commands as requests John Garry
2022-06-09 10:29 ` [PATCH RFC v2 18/18] scsi: libsas drivers: Remove private tag management John Garry
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