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From: Ming Lei <ming.lei@redhat.com>
To: Christoph Hellwig <hch@lst.de>
Cc: Jens Axboe <axboe@kernel.dk>,
	linux-block@vger.kernel.org, John Garry <john.garry@huawei.com>,
	Bart Van Assche <bvanassche@acm.org>,
	Hannes Reinecke <hare@suse.com>,
	Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH V11 06/12] blk-mq: prepare for draining IO when hctx's all CPUs are offline
Date: Thu, 14 May 2020 08:33:40 +0800	[thread overview]
Message-ID: <20200514003340.GA2073570@T590> (raw)
In-Reply-To: <20200513115832.GB6297@lst.de>

On Wed, May 13, 2020 at 01:58:32PM +0200, Christoph Hellwig wrote:
> I think the flag should be inverted, indicated managed irqs if set.
> And we should fine a a way to automatically set it from the managed
> IRQ blk_mq_*_map_queues helpers instead of leaving the decisions to

blk_mq_*_map_queues doesn't tell us if managed IRQ is used, only the
driver knows that.

> the driver author that is most likely going to get it wrong, especially
> for SCSI, where the actual driver can't even get at the current flag.
> 

BLK_MQ_F_NO_MANAGED_IRQ is just for avoiding deadlock in draining IO
during cpu hotplug. So far, only stacking blk-mq drivers need this flag.

That is why the flag is named as NO_MANAGED_IRQ, or we may add flag of
BLK_MQ_F_STACKING for this purpose too.

thanks,
Ming


  reply	other threads:[~2020-05-14  0:34 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-13  3:47 [PATCH V11 00/12] blk-mq: improvement CPU hotplug Ming Lei
2020-05-13  3:47 ` [PATCH V11 01/12] block: clone nr_integrity_segments and write_hint in blk_rq_prep_clone Ming Lei
2020-05-13  3:47 ` [PATCH V11 02/12] block: add helper for copying request Ming Lei
2020-05-13  3:47 ` [PATCH V11 03/12] blk-mq: mark blk_mq_get_driver_tag as static Ming Lei
2020-05-13  3:47 ` [PATCH V11 04/12] blk-mq: assign rq->tag in blk_mq_get_driver_tag Ming Lei
2020-05-13  3:47 ` [PATCH V11 05/12] blk-mq: add blk_mq_all_tag_iter Ming Lei
2020-05-13 11:56   ` Christoph Hellwig
2020-05-13  3:47 ` [PATCH V11 06/12] blk-mq: prepare for draining IO when hctx's all CPUs are offline Ming Lei
2020-05-13  6:35   ` Hannes Reinecke
2020-05-13 11:58   ` Christoph Hellwig
2020-05-14  0:33     ` Ming Lei [this message]
2020-05-13  3:47 ` [PATCH V11 07/12] blk-mq: stop to handle IO and drain IO before hctx becomes inactive Ming Lei
2020-05-13 11:59   ` Christoph Hellwig
2020-05-14  0:36     ` Ming Lei
2020-05-14  1:12     ` Bart Van Assche
2020-05-14  3:10     ` Ming Lei
2020-05-13  3:47 ` [PATCH V11 08/12] block: add blk_end_flush_machinery Ming Lei
2020-05-13 12:00   ` Christoph Hellwig
2020-05-13  3:48 ` [PATCH V11 09/12] blk-mq: add blk_mq_hctx_handle_dead_cpu for handling cpu dead Ming Lei
2020-05-13 12:06   ` Christoph Hellwig
2020-05-13  3:48 ` [PATCH V11 10/12] block: add request allocation flag of BLK_MQ_REQ_FORCE Ming Lei
2020-05-13 10:34   ` [PATCH V12 " Ming Lei
2020-05-13  3:48 ` [PATCH V11 11/12] blk-mq: re-submit IO in case that hctx is inactive Ming Lei
2020-05-13  9:21   ` John Garry
2020-05-13 12:21   ` Christoph Hellwig
2020-05-13 15:03     ` Bart Van Assche
2020-05-14  0:45       ` Ming Lei
2020-05-14  0:40     ` Ming Lei
2020-05-13  3:48 ` [PATCH V11 12/12] block: deactivate hctx when the hctx is actually inactive Ming Lei
2020-05-13  7:34 ` [PATCH V11 00/12] blk-mq: improvement CPU hotplug John Garry
2020-05-13 10:37   ` Ming Lei
2020-05-13 11:33     ` John Garry

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