From: Christoph Hellwig <hch@infradead.org>
To: Damien Le Moal <damien.lemoal@wdc.com>
Cc: linux-block@vger.kernel.org, Jens Axboe <axboe@kernel.dk>,
linux-scsi@vger.kernel.org,
"Martin K . Petersen" <martin.petersen@oracle.com>
Subject: Re: [PATCH v2 5/7] block: Delay default elevator initialization
Date: Tue, 3 Sep 2019 02:02:47 -0700 [thread overview]
Message-ID: <20190903090247.GE23783@infradead.org> (raw)
In-Reply-To: <20190828022947.23364-6-damien.lemoal@wdc.com>
On Wed, Aug 28, 2019 at 11:29:45AM +0900, Damien Le Moal wrote:
> When elevator_init_mq() is called from blk_mq_init_allocated_queue(),
> the only information known about the device is the number of hardware
> queues as the block device scan by the device driver is not completed
> yet. The device type and the device required features are not set yet,
> preventing to correctly choose the default elevator most suitable for
> the device.
>
> This currently affects all multi-queue zoned block devices which default
> to the "none" elevator instead of the required "mq-deadline" elevator.
> These drives currently include host-managed SMR disks connected to a
> smartpqi HBA and null_blk block devices with zoned mode enabled.
> Upcoming NVMe Zoned Namespace devices will also be affected.
>
> Fix this by moving the execution of elevator_init_mq() from
> blk_mq_init_allocated_queue() into __device_add_disk() to allow for the
> device driver to probe the device characteristics and set attributes
> of the device request queue prior to the elevator initialization.
>
> Also to make sure that the elevator initialization is never done while
> requests are in-flight (there should be none when the device driver
> calls device_add_disk()), freeze and quiesce the device request queue
> before executing blk_mq_init_sched().
So the disk can be accessed from userspace or partition probing once we
registered the region. Based on that I think it would be better if
we set the elevator a little earlier before that happens. With that
we shouldn't have to freeze the queue.
next prev parent reply other threads:[~2019-09-03 9:02 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-28 2:29 [PATCH v2 0/7] Elevator cleanups and improvements Damien Le Moal
2019-08-28 2:29 ` [PATCH v2 1/7] block: Cleanup elevator_init_mq() use Damien Le Moal
2019-09-03 8:55 ` Christoph Hellwig
2019-08-28 2:29 ` [PATCH v2 2/7] block: Change elevator_init_mq() to always succeed Damien Le Moal
2019-09-03 8:55 ` Christoph Hellwig
2019-08-28 2:29 ` [PATCH v2 3/7] block: Introduce elevator features Damien Le Moal
2019-08-28 8:16 ` Johannes Thumshirn
2019-08-28 10:41 ` Damien Le Moal
2019-08-28 10:43 ` Johannes Thumshirn
2019-08-28 11:08 ` Damien Le Moal
2019-08-28 11:11 ` Johannes Thumshirn
2019-09-03 8:56 ` Christoph Hellwig
2019-08-28 2:29 ` [PATCH v2 4/7] block: Improve default elevator selection Damien Le Moal
2019-09-03 8:57 ` Christoph Hellwig
2019-09-04 8:42 ` Damien Le Moal
2019-08-28 2:29 ` [PATCH v2 5/7] block: Delay default elevator initialization Damien Le Moal
2019-09-03 9:02 ` Christoph Hellwig [this message]
2019-09-04 2:07 ` Damien Le Moal
2019-09-04 6:47 ` Christoph Hellwig
2019-08-28 2:29 ` [PATCH v2 6/7] block: Set ELEVATOR_F_ZBD_SEQ_WRITE for nullblk zoned disks Damien Le Moal
2019-09-03 9:03 ` Christoph Hellwig
2019-08-28 2:29 ` [PATCH v2 7/7] scsi: Set ELEVATOR_F_ZBD_SEQ_WRITE for ZBC disks Damien Le Moal
2019-09-03 9:03 ` Christoph Hellwig
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