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From: Christoph Hellwig <hch@infradead.org>
To: Hannes Reinecke <hare@suse.de>
Cc: Christoph Hellwig <hch@infradead.org>,
	Mike Snitzer <snitzer@redhat.com>, Jeff Moyer <jmoyer@redhat.com>,
	Jens Axboe <axboe@kernel.dk>, Shaohua Li <shli@fusionio.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 1/1] block: rework flush sequencing for blk-mq
Date: Fri, 14 Mar 2014 05:44:57 -0700	[thread overview]
Message-ID: <20140314124457.GA4859@infradead.org> (raw)
In-Reply-To: <5322CC4D.8040509@suse.de>

On Fri, Mar 14, 2014 at 10:30:53AM +0100, Hannes Reinecke wrote:
> That was actually one of my plans, move dm-multipath over to use
> blk-mq. But then I'd need to discuss with Jens et al how to best
> achieve this; the current static hctx allocation doesn't play well
> with multipaths dynamic path management.

I'd say it the other way around: the clone + insert hacks in
dm-multipath don't work well with blk-mq.  Not allowing non-owned
requests is fundamentally part of the blk-mq model to allow things
like the integrated tag allocator and queue depth limiting or the
preallocated driver specific data.

Instead dm-multipath should alway resubmit the request like it already
does for the slow path for the first step.  Longer term we might be able
to operate using a cheaper temporary structure, but I'm not sure that's
going to be worth it.

  reply	other threads:[~2014-03-14 12:45 UTC|newest]

Thread overview: 40+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-01-30 13:26 [PATCH 0/1] block: rework flush sequencing for blk-mq Christoph Hellwig
2014-01-30 13:26 ` [PATCH 1/1] " Christoph Hellwig
2014-02-07  1:18   ` Shaohua Li
2014-02-07 14:19     ` Christoph Hellwig
2014-02-08  0:55       ` Shaohua Li
2014-02-10 10:33         ` Christoph Hellwig
2014-03-07 20:45   ` Jeff Moyer
2014-03-08 15:52     ` Christoph Hellwig
2014-03-08 17:33       ` Mike Snitzer
2014-03-08 19:51         ` Hannes Reinecke
2014-03-08 18:13           ` Mike Snitzer
2014-03-08 21:33             ` Hannes Reinecke
2014-03-08 22:09               ` [PATCH] block: fix q->flush_rq NULL pointer crash on dm-mpath flush Mike Snitzer
2014-03-09  0:24                 ` Jens Axboe
2014-03-09  0:57                   ` Mike Snitzer
2014-03-09  3:18                     ` Jens Axboe
2014-03-09  3:29                       ` Mike Snitzer
2014-03-12 10:28           ` [PATCH 1/1] block: rework flush sequencing for blk-mq Christoph Hellwig
2014-03-12 10:50             ` Hannes Reinecke
2014-03-12 10:55               ` Christoph Hellwig
2014-03-12 11:07                 ` Hannes Reinecke
     [not found]               ` <53203BE5.402-l3A5Bk7waGM@public.gmane.org>
2014-03-12 11:00                 ` SuSE O_DIRECT|O_NONBLOCK overload Christoph Hellwig
2014-03-12 11:00                   ` Christoph Hellwig
     [not found]                   ` <20140312110015.GA29907-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
2014-03-13  0:15                     ` NeilBrown
2014-03-13  0:15                       ` NeilBrown
     [not found]                       ` <20140313111555.2f15f19f-wvvUuzkyo1EYVZTmpyfIwg@public.gmane.org>
2014-03-14 17:46                         ` Mike Christie
2014-03-14 17:46                           ` Mike Christie
2014-03-13 16:13             ` [PATCH 1/1] block: rework flush sequencing for blk-mq Mike Snitzer
2014-03-14  9:25               ` Christoph Hellwig
2014-03-14  9:30                 ` Hannes Reinecke
2014-03-14 12:44                   ` Christoph Hellwig [this message]
2014-03-14  9:34                 ` Christoph Hellwig
2014-03-14  9:52                   ` Hannes Reinecke
2014-03-14 10:58                     ` Christoph Hellwig
2014-03-14 11:10                       ` Hannes Reinecke
2014-03-14 13:00                 ` Mike Snitzer
2014-03-14 13:23                   ` Christoph Hellwig
2014-03-14 14:13                     ` Mike Snitzer
2014-03-15 13:28                       ` scsi_debug and mutipath, was " Christoph Hellwig
2014-03-17 11:55                       ` [dm-devel] " Bryn M. Reeves

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