From: Christoph Hellwig <hch@lst.de>
To: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Cc: Hannes Reinecke <hare@suse.de>,
John Garry <john.garry@huawei.com>,
Bart Van Assche <bvanassche@acm.org>,
axboe@kernel.dk, jejb@linux.ibm.com, martin.petersen@oracle.com,
brking@us.ibm.com, hch@lst.de, 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 11:05:43 +0200 [thread overview]
Message-ID: <20220620090543.GA13643@lst.de> (raw)
In-Reply-To: <9de5ed1b-e874-28ac-0532-cd5420892064@opensource.wdc.com>
On Mon, Jun 20, 2022 at 06:02:30PM +0900, Damien Le Moal wrote:
> So reserving a tag/req to be able to do NCQ at the cost of max qd being 31
> works for that. We could keep max qd at 32 by creating one more "fake" tag
> and having a request for it, that is, having the fake tag visible to the
> block layer as a reserved tag, as John's series is doing, but for the
> reserved tags, we actually need to use an effective tag (qc->hw_tag) when
> issuing the commands. And for that, we can reuse the tag of one of the
> failed commands.
Take a look at the magic flush request in blk-flush.c, which is
preallocated but borrows a tag from the request that wants a pre- or
post-flush. The logic is rather ugly, but maybe it might actually
become cleaner by generalizing it a bit.
next prev parent reply other threads:[~2022-06-20 9:06 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 [this message]
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
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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