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From: Wouter Verhelst <w@uter.be>
To: Josef Bacik <jbacik@fb.com>
Cc: linux-block@vger.kernel.org, mpa@pengutronix.de,
	kernel-team@fb.com, nbd-general@lists.sourceforge.net,
	linux-kernel@vger.kernel.org
Subject: Re: [Nbd] [RESEND][PATCH 0/5] nbd improvements
Date: Thu, 15 Sep 2016 12:49:35 +0200	[thread overview]
Message-ID: <20160915104935.ohuwgq2chsedz6fl@grep.be> (raw)
In-Reply-To: <20160909200203.phhvodsfs7ymukfp@grep.be>

Hi,

On Fri, Sep 09, 2016 at 10:02:03PM +0200, Wouter Verhelst wrote:
> I see some practical problems with this:
[...]

One more that I didn't think about earlier:

A while back, we spent quite some time defining the semantics of the
various commands in the face of the NBD_CMD_FLUSH and NBD_CMD_FLAG_FUA
write barriers. At the time, we decided that it would be unreasonable
to expect servers to make these write barriers effective across
different connections.

Since my knowledge of kernel internals is limited, I tried finding some
documentation on this, but I guess that either it doesn't exist or I'm
looking in the wrong place; therefore, am I correct in assuming that
blk-mq knows about such semantics, and will handle them correctly (by
either sending a write barrier to all queues, or not making assumptions
about write barriers that were sent over a different queue)? If not,
this may be something that needs to be taken care of.

Thanks,

-- 
< ron> I mean, the main *practical* problem with C++, is there's like a dozen
       people in the world who think they really understand all of its rules,
       and pretty much all of them are just lying to themselves too.
 -- #debian-devel, OFTC, 2016-02-12

  parent reply	other threads:[~2016-09-15 10:50 UTC|newest]

Thread overview: 59+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-09-08 21:12 [RESEND][PATCH 0/5] nbd improvements Josef Bacik
2016-09-08 21:12 ` [PATCH 1/5] nbd: convert to blkmq Josef Bacik
2016-09-08 21:12 ` [PATCH 2/5] nbd: don't shutdown sock with irq's disabled Josef Bacik
2016-09-08 21:12 ` [PATCH 3/5] nbd: use flags instead of bool Josef Bacik
2016-09-09  1:20   ` Joe Perches
2016-09-09 13:55     ` Jens Axboe
2016-09-09 16:04       ` Joe Perches
2016-09-09 16:11         ` Jens Axboe
2016-09-09 16:15           ` Joe Perches
2016-09-09 16:20             ` Jens Axboe
2016-09-08 21:12 ` [PATCH 4/5] nbd: allow block mq to deal with timeouts Josef Bacik
2016-09-08 21:12 ` [PATCH 5/5] nbd: add multi-connection support Josef Bacik
2016-09-10  7:43   ` Christoph Hellwig
2016-09-12 13:11     ` Josef Bacik
2016-09-09 20:02 ` [Nbd] [RESEND][PATCH 0/5] nbd improvements Wouter Verhelst
2016-09-09 20:36   ` Josef Bacik
2016-09-09 20:55     ` Wouter Verhelst
2016-09-09 23:00       ` Josef Bacik
2016-09-09 23:37         ` Jens Axboe
2016-09-15 10:49   ` Wouter Verhelst [this message]
2016-09-15 11:09     ` Alex Bligh
2016-09-15 11:29       ` Wouter Verhelst
2016-09-15 11:40         ` Christoph Hellwig
2016-09-15 11:46           ` Alex Bligh
2016-09-15 11:52             ` Christoph Hellwig
2016-09-15 12:01               ` Wouter Verhelst
2016-09-15 12:20                 ` Christoph Hellwig
2016-09-15 12:26                   ` Wouter Verhelst
2016-09-15 12:27                     ` Christoph Hellwig
2016-09-15 12:04               ` Alex Bligh
2016-09-15 11:39       ` Christoph Hellwig
2016-09-15 13:34       ` Eric Blake
2016-09-15 14:07         ` Paolo Bonzini
2016-09-15 15:23           ` Alex Bligh
2016-09-15 21:10             ` Paolo Bonzini
2016-09-15 15:25         ` Alex Bligh
2016-09-15 11:38     ` Christoph Hellwig
2016-09-15 11:43       ` Alex Bligh
2016-09-15 11:46         ` Christoph Hellwig
2016-09-15 11:56           ` Alex Bligh
2016-09-15 11:55       ` Wouter Verhelst
2016-09-15 12:01         ` Christoph Hellwig
2016-09-15 12:11           ` Alex Bligh
2016-09-15 12:18             ` Christoph Hellwig
2016-09-15 12:28               ` Alex Bligh
2016-09-15 12:21           ` Wouter Verhelst
2016-09-15 12:23             ` Christoph Hellwig
2016-09-15 12:33               ` Alex Bligh
2016-09-15 12:36                 ` Christoph Hellwig
2016-09-15 12:39                   ` Alex Bligh
2016-09-15 12:41                     ` Christoph Hellwig
2016-09-15 12:44                       ` Alex Bligh
2016-09-15 13:17                         ` Wouter Verhelst
2016-09-15 13:57                           ` Josef Bacik
2016-09-15 15:17                             ` Alex Bligh
2016-09-15 16:08                           ` Alex Bligh
2016-09-15 16:27                             ` Wouter Verhelst
2016-09-15 16:42                               ` Alex Bligh
2016-09-15 19:02                               ` Eric Blake

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