From: Ming Lei <ming.lei@redhat.com>
To: Damien Le Moal <damien.lemoal@wdc.com>
Cc: linux-scsi@vger.kernel.org,
"Martin K . Petersen" <martin.petersen@oracle.com>,
linux-block@vger.kernel.org, Jens Axboe <axboe@kernel.dk>,
Christoph Hellwig <hch@lst.de>,
Bart Van Assche <Bart.VanAssche@wdc.com>
Subject: Re: [PATCH V2 10/12] scsi: sd_zbc: Disable zone write locking with scsi-mq
Date: Fri, 8 Sep 2017 20:43:30 +0800 [thread overview]
Message-ID: <20170908124329.GA18932@ming.t460p> (raw)
In-Reply-To: <20170907161640.30465-11-damien.lemoal@wdc.com>
Hi Damien,
On Fri, Sep 08, 2017 at 01:16:38AM +0900, Damien Le Moal wrote:
> In the case of a ZBC disk used with scsi-mq, zone write locking does
> not prevent write reordering in sequential zones. Unlike the legacy
> case, zone locking can only be done after the command request is
> removed from the scheduler dispatch queue. That is, at the time of
> zone locking, the write command may already be out of order.
Per my understanding, for legacy case, it can be quite tricky to let
the existed I/O scheduler guarantee the write order for ZBC disk.
I guess requeue still might cause write reorder even in legacy path,
since requeue can happen in both scsi_request_fn() and scsi_io_completion()
with q->queue_lock released, meantime new rq belonging to the same
zone can come and be inserted to queue.
>
> Disable zone write locking in sd_zbc_write_lock_zone() if the disk is
> used with scsi-mq. Write order guarantees can be provided by an
> adapted I/O scheduler.
Sounds a good idea to enhance the order in a new scheduler, will
look at the following patch.
--
Ming
next prev parent reply other threads:[~2017-09-08 12:43 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-07 16:16 [PATCH V2 00/12] scsi-mq support for ZBC disks Damien Le Moal
2017-09-07 16:16 ` [PATCH V2 01/12] block: Fix declaration of blk-mq debugfs functions Damien Le Moal
2017-09-08 8:05 ` Johannes Thumshirn
2017-09-07 16:16 ` [PATCH V2 02/12] block: Fix declaration of blk-mq scheduler functions Damien Le Moal
2017-09-08 8:05 ` Johannes Thumshirn
2017-09-07 16:16 ` [PATCH V2 03/12] scsi: sd_zbc: Move ZBC declarations to scsi_proto.h Damien Le Moal
2017-09-08 8:10 ` Johannes Thumshirn
2017-09-07 16:16 ` [PATCH V2 04/12] scsi: sd_zbc: Move zbc disk declarations to sd_zbc.h Damien Le Moal
2017-09-08 8:11 ` Johannes Thumshirn
2017-09-07 16:16 ` [PATCH V2 05/12] scsi: sd_zbc: Fix comments and indentation Damien Le Moal
2017-09-08 8:12 ` Johannes Thumshirn
2017-09-07 16:16 ` [PATCH V2 06/12] scsi: sd_zbc: Rearrange code Damien Le Moal
2017-09-08 8:13 ` Johannes Thumshirn
2017-09-07 16:16 ` [PATCH V2 07/12] scsi: sd_zbc.c: Use well defined macros Damien Le Moal
2017-09-08 8:15 ` Johannes Thumshirn
2017-09-07 16:16 ` [PATCH V2 08/12] scsi: sd_zbc: Fix sd_zbc_read_zoned_characteristics() Damien Le Moal
2017-09-08 8:17 ` Johannes Thumshirn
2017-09-07 16:16 ` [PATCH V2 09/12] scsi: sd_zbc: Limit zone write locking to sequential zones Damien Le Moal
2017-09-08 8:39 ` Johannes Thumshirn
2017-09-08 9:48 ` Christoph Hellwig
2017-09-08 9:50 ` Johannes Thumshirn
2017-09-07 16:16 ` [PATCH V2 10/12] scsi: sd_zbc: Disable zone write locking with scsi-mq Damien Le Moal
2017-09-08 12:43 ` Ming Lei [this message]
2017-09-08 16:53 ` Damien Le Moal
2017-09-10 5:10 ` Ming Lei
2017-09-12 8:24 ` Damien Le Moal
2017-09-12 9:26 ` Ming Lei
2017-09-13 0:13 ` Damien Le Moal
2017-09-07 16:16 ` [PATCH V2 11/12] scsi: sd: Introduce scsi_disk_from_queue() Damien Le Moal
2017-09-10 5:16 ` Ming Lei
2017-09-12 8:05 ` Damien Le Moal
2017-09-07 16:16 ` [PATCH V2 12/12] scsi: Introduce ZBC disk I/O scheduler Damien Le Moal
2017-09-08 8:20 ` [PATCH V2 00/12] scsi-mq support for ZBC disks Christoph Hellwig
2017-09-08 16:12 ` Damien Le Moal
2017-09-11 12:24 ` Christoph Hellwig
2017-09-12 8:38 ` Damien Le Moal
2017-09-13 20:17 ` Christoph Hellwig
2017-09-14 0:04 ` Damien Le Moal
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