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From: Ming Lei <ming.lei@redhat.com>
To: Christoph Hellwig <hch@infradead.org>
Cc: Jens Axboe <axboe@kernel.dk>,
	linux-block@vger.kernel.org, dm-devel@redhat.com,
	Mike Snitzer <snitzer@redhat.com>
Subject: Re: [dm-devel] [PATCH 0/3] blk-mq/dm-rq: support BLK_MQ_F_BLOCKING for dm-rq
Date: Thu, 23 Dec 2021 12:16:20 +0800	[thread overview]
Message-ID: <YcP4FMG9an5ReIiV@T590> (raw)
In-Reply-To: <YcH/E4JNag0QYYAa@infradead.org>

On Tue, Dec 21, 2021 at 08:21:39AM -0800, Christoph Hellwig wrote:
> On Tue, Dec 21, 2021 at 10:14:56PM +0800, Ming Lei wrote:
> > Hello,
> > 
> > dm-rq may be built on blk-mq device which marks BLK_MQ_F_BLOCKING, so
> > dm_mq_queue_rq() may become to sleep current context.
> > 
> > Fixes the issue by allowing dm-rq to set BLK_MQ_F_BLOCKING in case that
> > any underlying queue is marked as BLK_MQ_F_BLOCKING.
> > 
> > DM request queue is allocated before allocating tagset, this way is a
> > bit special, so we need to pre-allocate srcu payload, then use the queue
> > flag of QUEUE_FLAG_BLOCKING for locking dispatch.
> 
> What is the benefit over just forcing bio-based dm-mpath for these
> devices?

At least IO scheduler can't be used for bio based dm-mpath, also there should
be other drawbacks for bio based mpath and request mpath is often the default
option, maybe Mike has more input about bio vs request dm-mpath.



Thanks,
Ming

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https://listman.redhat.com/mailman/listinfo/dm-devel


WARNING: multiple messages have this Message-ID (diff)
From: Ming Lei <ming.lei@redhat.com>
To: Christoph Hellwig <hch@infradead.org>
Cc: Jens Axboe <axboe@kernel.dk>, Mike Snitzer <snitzer@redhat.com>,
	linux-block@vger.kernel.org, dm-devel@redhat.com
Subject: Re: [PATCH 0/3] blk-mq/dm-rq: support BLK_MQ_F_BLOCKING for dm-rq
Date: Thu, 23 Dec 2021 12:16:20 +0800	[thread overview]
Message-ID: <YcP4FMG9an5ReIiV@T590> (raw)
In-Reply-To: <YcH/E4JNag0QYYAa@infradead.org>

On Tue, Dec 21, 2021 at 08:21:39AM -0800, Christoph Hellwig wrote:
> On Tue, Dec 21, 2021 at 10:14:56PM +0800, Ming Lei wrote:
> > Hello,
> > 
> > dm-rq may be built on blk-mq device which marks BLK_MQ_F_BLOCKING, so
> > dm_mq_queue_rq() may become to sleep current context.
> > 
> > Fixes the issue by allowing dm-rq to set BLK_MQ_F_BLOCKING in case that
> > any underlying queue is marked as BLK_MQ_F_BLOCKING.
> > 
> > DM request queue is allocated before allocating tagset, this way is a
> > bit special, so we need to pre-allocate srcu payload, then use the queue
> > flag of QUEUE_FLAG_BLOCKING for locking dispatch.
> 
> What is the benefit over just forcing bio-based dm-mpath for these
> devices?

At least IO scheduler can't be used for bio based dm-mpath, also there should
be other drawbacks for bio based mpath and request mpath is often the default
option, maybe Mike has more input about bio vs request dm-mpath.



Thanks,
Ming


  reply	other threads:[~2021-12-23  4:17 UTC|newest]

Thread overview: 40+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-12-21 14:14 [dm-devel] [PATCH 0/3] blk-mq/dm-rq: support BLK_MQ_F_BLOCKING for dm-rq Ming Lei
2021-12-21 14:14 ` Ming Lei
2021-12-21 14:14 ` [dm-devel] [PATCH 1/3] block: split having srcu from queue blocking Ming Lei
2021-12-21 14:14   ` Ming Lei
2022-01-11 18:13   ` [dm-devel] " Jeff Moyer
2022-01-11 18:13     ` Jeff Moyer
2021-12-21 14:14 ` [dm-devel] [PATCH 2/3] block: add blk_alloc_disk_srcu Ming Lei
2021-12-21 14:14   ` Ming Lei
2022-01-11 18:13   ` [dm-devel] " Jeff Moyer
2022-01-11 18:13     ` Jeff Moyer
2021-12-21 14:14 ` [dm-devel] [PATCH 3/3] dm: mark dm queue as blocking if any underlying is blocking Ming Lei
2021-12-21 14:14   ` Ming Lei
2022-01-06 15:40   ` [dm-devel] " Mike Snitzer
2022-01-06 15:40     ` Mike Snitzer
2022-01-06 15:51     ` [dm-devel] " Ming Lei
2022-01-06 15:51       ` Ming Lei
2022-01-10 19:23       ` [dm-devel] " Mike Snitzer
2022-01-10 19:23         ` Mike Snitzer
2022-01-11 18:14   ` [dm-devel] " Jeff Moyer
2022-01-11 18:14     ` Jeff Moyer
2021-12-21 16:21 ` [dm-devel] [PATCH 0/3] blk-mq/dm-rq: support BLK_MQ_F_BLOCKING for dm-rq Christoph Hellwig
2021-12-21 16:21   ` Christoph Hellwig
2021-12-23  4:16   ` Ming Lei [this message]
2021-12-23  4:16     ` Ming Lei
2021-12-28 21:30     ` [dm-devel] " Mike Snitzer
2021-12-28 21:30       ` Mike Snitzer
2022-01-10 19:26       ` [dm-devel] " Mike Snitzer
2022-01-10 19:26         ` Mike Snitzer
2022-01-11  8:34       ` [dm-devel] " Christoph Hellwig
2022-01-11  8:34         ` Christoph Hellwig
2022-01-11 16:15         ` Mike Snitzer
2022-01-11 16:15           ` Mike Snitzer
2022-01-17  8:08           ` [dm-devel] " Christoph Hellwig
2022-01-17  8:08             ` Christoph Hellwig
2022-01-11 18:23         ` Jeff Moyer
2022-01-11 18:23           ` Jeff Moyer
2022-01-17  8:10           ` Christoph Hellwig
2022-01-17  8:10             ` Christoph Hellwig
2022-01-19 21:03             ` Mike Snitzer
2022-01-19 21:03               ` Mike Snitzer

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