From: Christoph Hellwig <hch@lst.de>
To: Ming Lei <ming.lei@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>, Jens Axboe <axboe@kernel.dk>,
"Martin K . Petersen" <martin.petersen@oracle.com>,
linux-block@vger.kernel.org, linux-nvme@lists.infradead.org,
linux-scsi@vger.kernel.org, Bart Van Assche <bvanassche@acm.org>
Subject: Re: [PATCH V2 09/13] scsi: force unfreezing queue into atomic mode
Date: Wed, 26 Jan 2022 09:15:04 +0100 [thread overview]
Message-ID: <20220126081504.GB23154@lst.de> (raw)
In-Reply-To: <Ye+605vZEyx3ofi2@T590>
On Tue, Jan 25, 2022 at 04:54:43PM +0800, Ming Lei wrote:
> > So what is the advantage of trying to remove the freeze from where
> > it belongs (common unregister code) while keeping it where it is a bandaid
> > (driver specific unregister code)?
>
> freeze in common unregister code is actually not good, because it provide
> nothing for bio based driver, so we can't move blk-cgroup shutdown into
> del_gendisk. Also we can't move elevator shutdown to del_gendisk for
> similar reason.
>
> Secondly freeze is pretty slow in percpu mode, so why slow down removing every
> disk just for scsi's bandaid?
I'd frame this differently:
- del_gendisk is the right place to freeze the queue, as that is where the
gendisk is unregistered and all fs I/O needs to stop. If we don't get
all aspects right we need to fix. As mentioned I'm already looking into
keeping a reference for the bio life time for bio based drivers.
- SCSI is the only driver that ever submits passthrough I/O without the
gendisk. So doing an additional freeze during request_queue teardown
is only needed for SCSI and we can eventually remove that for everyone
else. And most of your series already does really good work towards that
goal!
>
>
> Thanks,
> Ming
---end quoted text---
next prev parent reply other threads:[~2022-01-26 8:15 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-22 11:10 [PATCH V2 00/13] block: don't drain file system I/O on del_gendisk Ming Lei
2022-01-22 11:10 ` [PATCH V2 01/13] block: declare blkcg_[init|exit]_queue in private header Ming Lei
2022-01-24 12:59 ` Christoph Hellwig
2022-01-22 11:10 ` [PATCH V2 02/13] block: move initialization of q->blkg_list into blkcg_init_queue Ming Lei
2022-01-24 13:00 ` Christoph Hellwig
2022-01-24 18:32 ` Bart Van Assche
2022-01-22 11:10 ` [PATCH V2 03/13] block: move blkcg initialization/destroy into disk allocation/release handler Ming Lei
2022-01-24 13:02 ` Christoph Hellwig
2022-01-22 11:10 ` [PATCH V2 04/13] block/wbt: fix negative inflight counter when remove scsi device Ming Lei
2022-02-17 7:45 ` Christoph Hellwig
2022-02-17 14:53 ` Jens Axboe
2022-01-22 11:10 ` [PATCH V2 05/13] block: only account passthrough IO from userspace Ming Lei
2022-01-24 13:05 ` Christoph Hellwig
2022-01-24 23:09 ` Ming Lei
2022-01-25 6:16 ` Christoph Hellwig
2022-01-25 7:19 ` Christoph Hellwig
2022-01-25 8:35 ` Ming Lei
2022-01-25 9:09 ` Ming Lei
2022-01-26 5:50 ` Christoph Hellwig
2022-01-26 7:21 ` Ming Lei
2022-01-26 8:10 ` Christoph Hellwig
2022-01-26 8:33 ` Ming Lei
2022-01-26 8:49 ` Christoph Hellwig
2022-01-26 9:59 ` Ming Lei
2022-01-26 16:37 ` Christoph Hellwig
2022-01-22 11:10 ` [PATCH V2 06/13] block: don't remove hctx debugfs dir from blk_mq_exit_queue Ming Lei
2022-01-24 13:06 ` Christoph Hellwig
2022-01-22 11:10 ` [PATCH V2 07/13] block: move q_usage_counter release into blk_queue_release Ming Lei
2022-01-24 13:09 ` Christoph Hellwig
2022-01-24 19:06 ` Bart Van Assche
2022-01-22 11:10 ` [PATCH V2 08/13] block: export __blk_mq_unfreeze_queue Ming Lei
2022-01-24 13:11 ` Christoph Hellwig
2022-01-22 11:10 ` [PATCH V2 09/13] scsi: force unfreezing queue into atomic mode Ming Lei
2022-01-24 13:15 ` Christoph Hellwig
2022-01-24 23:21 ` Ming Lei
2022-01-25 7:27 ` Christoph Hellwig
2022-01-25 8:54 ` Ming Lei
2022-01-26 8:15 ` Christoph Hellwig [this message]
2022-01-22 11:10 ` [PATCH V2 10/13] block: add helper of disk_release_queue for release queue data for disk Ming Lei
2022-01-24 13:16 ` Christoph Hellwig
2022-01-24 23:27 ` Ming Lei
2022-01-25 6:17 ` Christoph Hellwig
2022-01-22 11:10 ` [PATCH V2 11/13] block: move blk_exit_queue into disk_release Ming Lei
2022-01-24 13:22 ` Christoph Hellwig
2022-01-24 23:38 ` Ming Lei
2022-01-22 11:10 ` [PATCH V2 12/13] block: move rq_qos_exit() into disk_release() Ming Lei
2022-01-24 13:28 ` Christoph Hellwig
2022-01-22 11:10 ` [PATCH V2 13/13] block: don't drain file system I/O on del_gendisk Ming Lei
2022-01-24 13:39 ` Christoph Hellwig
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