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From: Wouter Verhelst <w@uter.be>
To: Christoph Hellwig <hch@infradead.org>
Cc: "nbd-general@lists.sourceforge.net"
	<nbd-general@lists.sourceforge.net>,
	linux-block@vger.kernel.org, Josef Bacik <jbacik@fb.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Markus Pargmann <mpa@pengutronix.de>,
	kernel-team@fb.com
Subject: Re: [Nbd] [RESEND][PATCH 0/5] nbd improvements
Date: Thu, 15 Sep 2016 14:26:31 +0200	[thread overview]
Message-ID: <20160915122631.7wus5o6qin6o7uz5@grep.be> (raw)
In-Reply-To: <20160915122008.GB1155@infradead.org>

On Thu, Sep 15, 2016 at 05:20:08AM -0700, Christoph Hellwig wrote:
> On Thu, Sep 15, 2016 at 02:01:59PM +0200, Wouter Verhelst wrote:
> > Yes. There was some discussion on that part, and we decided that setting
> > the flag doesn't hurt, but the spec also clarifies that using it on READ
> > does nothing, semantically.
> >
> > 
> > The problem is that there are clients in the wild which do set it on
> > READ, so it's just a matter of "be liberal in what you accept".
> 
> Note that FUA on READ in SCSI and NVMe does have a meaning - it
> requires you to bypass any sort of cache on the target.  I think it's an
> wrong defintion because it mandates implementation details that aren't
> observable by the initiator, but it's still the spec wording and nbd
> diverges from it.  That's not nessecarily a bad thing, but a caveat to
> look out for.

Yes. I think the kernel nbd driver should probably filter out FUA on
READ. It has no meaning in the case of nbd, and whatever expectations
the kernel may have cannot be provided for by nbd anyway.

-- 
< 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

  reply	other threads:[~2016-09-15 12:26 UTC|newest]

Thread overview: 95+ 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 16:04         ` Joe Perches
2016-09-09 16:11         ` Jens Axboe
2016-09-09 16:15           ` Joe Perches
2016-09-09 16:20             ` Jens Axboe
2016-09-09 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
2016-09-15 11:09     ` Alex Bligh
2016-09-15 11:09       ` Alex Bligh
2016-09-15 11:29       ` Wouter Verhelst
2016-09-15 11:29         ` Wouter Verhelst
2016-09-15 11:40         ` Christoph Hellwig
2016-09-15 11:40           ` Christoph Hellwig
2016-09-15 11:46           ` Alex Bligh
2016-09-15 11:46             ` Alex Bligh
2016-09-15 11:52             ` Christoph Hellwig
2016-09-15 11:52               ` Christoph Hellwig
2016-09-15 12:01               ` Wouter Verhelst
2016-09-15 12:01                 ` Wouter Verhelst
2016-09-15 12:20                 ` Christoph Hellwig
2016-09-15 12:20                   ` Christoph Hellwig
2016-09-15 12:26                   ` Wouter Verhelst [this message]
2016-09-15 12:26                     ` Wouter Verhelst
2016-09-15 12:27                     ` Christoph Hellwig
2016-09-15 12:27                       ` Christoph Hellwig
2016-09-15 12:04               ` Alex Bligh
2016-09-15 12:04                 ` Alex Bligh
2016-09-15 11:39       ` Christoph Hellwig
2016-09-15 11:39         ` Christoph Hellwig
2016-09-15 13:34       ` Eric Blake
2016-09-15 13:34         ` Eric Blake
2016-09-15 14:07         ` Paolo Bonzini
2016-09-15 14:07           ` Paolo Bonzini
2016-09-15 15:23           ` Alex Bligh
2016-09-15 15:23             ` Alex Bligh
2016-09-15 21:10             ` Paolo Bonzini
2016-09-15 21:10               ` Paolo Bonzini
2016-09-15 15:25         ` Alex Bligh
2016-09-15 15:25           ` Alex Bligh
2016-09-15 11:38     ` Christoph Hellwig
2016-09-15 11:43       ` Alex Bligh
2016-09-15 11:43         ` Alex Bligh
2016-09-15 11:46         ` Christoph Hellwig
2016-09-15 11:46           ` Christoph Hellwig
2016-09-15 11:56           ` Alex Bligh
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 12:11             ` Alex Bligh
2016-09-15 12:18             ` Christoph Hellwig
2016-09-15 12:18               ` Christoph Hellwig
2016-09-15 12:28               ` Alex Bligh
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 12:33                 ` Alex Bligh
2016-09-15 12:36                 ` Christoph Hellwig
2016-09-15 12:36                   ` Christoph Hellwig
2016-09-15 12:39                   ` Alex Bligh
2016-09-15 12:39                     ` Alex Bligh
2016-09-15 12:41                     ` Christoph Hellwig
2016-09-15 12:41                       ` Christoph Hellwig
2016-09-15 12:44                       ` Alex Bligh
2016-09-15 12:44                         ` Alex Bligh
2016-09-15 13:17                         ` Wouter Verhelst
2016-09-15 13:17                           ` Wouter Verhelst
2016-09-15 13:57                           ` Josef Bacik
2016-09-15 13:57                             ` Josef Bacik
2016-09-15 15:17                             ` Alex Bligh
2016-09-15 15:17                               ` Alex Bligh
2016-09-15 16:08                           ` Alex Bligh
2016-09-15 16:08                             ` Alex Bligh
2016-09-15 16:27                             ` Wouter Verhelst
2016-09-15 16:27                               ` Wouter Verhelst
2016-09-15 16:42                               ` Alex Bligh
2016-09-15 16:42                                 ` Alex Bligh
2016-09-15 19:02                               ` Eric Blake
2016-09-15 19:02                                 ` Eric Blake

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