From: Christoph Hellwig <hch@infradead.org>
To: Alex Bligh <alex@alex.org.uk>
Cc: Christoph Hellwig <hch@infradead.org>,
Wouter Verhelst <w@uter.be>,
"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>,
mpa@pengutronix.de, kernel-team@fb.com
Subject: Re: [Nbd] [RESEND][PATCH 0/5] nbd improvements
Date: Thu, 15 Sep 2016 05:18:18 -0700 [thread overview]
Message-ID: <20160915121818.GA1155@infradead.org> (raw)
In-Reply-To: <30DE0D1A-FAB1-43EE-A88E-ED6565719166@alex.org.uk>
On Thu, Sep 15, 2016 at 01:11:24PM +0100, Alex Bligh wrote:
> > NBD_CMD_FLUSH (3)
> >
> > A flush request; a write barrier.
>
> I can see that's potentially confusing as isn't meant to mean 'an old-style
> linux kernel block device write barrier'. I think in general terms it
> probably is some form of barrier, but I see no problem in deleting the
> words "a write barrier" from the spec text if only to make it
> clearer.
Yes, please do that. A "barrier" implies draining of the queue.
> However, I think the description of the command itself:
>
> > The server MUST NOT send a successful reply header for this request before all write requests for which a reply has already been sent to the client have reached permanent storage (using fsync() or similar).
>
> and the ordering section I pointed you to before, were both correct, yes?
Yes, this seems correct.
> actually fdatasync() technically does more than is necessary, as it
> will also flush commands that have been processed, but for which no
> reply has yet been sent - that's no bad thing.
Yes. But without an actual barrier it's hard to be exact - and
fdatasync does the right thing by including false positives.
next prev parent reply other threads:[~2016-09-15 12:18 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
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 [this message]
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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