From: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
To: Vivek Goyal <vgoyal@redhat.com>
Cc: hch@infradead.org, Jeremy Fitzhardinge <jeremy@goop.org>,
jbeulich@novell.com, linux-kernel@vger.kernel.org,
JBeulich@suse.com
Subject: Re: Help with implementing some form of barriers in 3.0 kernels.
Date: Wed, 7 Sep 2011 14:27:49 -0400 [thread overview]
Message-ID: <20110907182748.GC5888@dumpdata.com> (raw)
In-Reply-To: <20110907181740.GG31726@redhat.com>
On Wed, Sep 07, 2011 at 02:17:40PM -0400, Vivek Goyal wrote:
> On Wed, Sep 07, 2011 at 01:48:32PM -0400, Konrad Rzeszutek Wilk wrote:
> > Hey Christoph,
> >
> > I was wondering what you think is the proper way of implementing a
> > backend to support the 'barrier' type requests? We have this issue were
> > there are 2.6.36 type guests that still use barriers and we would like
> > to support them properly. But in 3.0 there are no barriers - hence
> > the question whether WRITE_fLUSH_FUA would be equal to WRITE_BARRIER?
>
> I think WRITE_FLUSH_FUA is not same as WRITE_BARRIER. Because it does
> not ensure request ordering. A request rq2 which is issued after rq1 (with
> WRITE_flush_FUA), can still finish before rq1. In the past WRITE_BARRIER
> would not allow that.
>
> So AFAIK, WRITE_flush_fua is not WRITE_BARRIER.
Ok, any thoughts on how to emulate it then perhaps? Mark each request after
rq1 with WRITE_FUA? .. But then how long should the _FUA bit be set - perhaps
until the rq1 has completed?
>
> Thanks
> Vivek
next prev parent reply other threads:[~2011-09-07 18:29 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-09-07 17:48 Help with implementing some form of barriers in 3.0 kernels Konrad Rzeszutek Wilk
2011-09-07 18:17 ` Vivek Goyal
2011-09-07 18:27 ` Konrad Rzeszutek Wilk [this message]
2011-09-07 18:36 ` Vivek Goyal
2011-09-07 20:16 ` Christoph Hellwig
2011-09-07 21:31 ` Vivek Goyal
2011-09-08 8:22 ` Christoph Hellwig
2011-09-08 8:02 ` Jan Beulich
2011-09-08 8:08 ` Christoph Hellwig
2011-09-13 10:44 ` Jan Beulich
2011-09-14 8:59 ` Konrad Rzeszutek Wilk
2011-09-14 9:12 ` Jan Beulich
2011-09-14 9:30 ` Konrad Rzeszutek Wilk
2011-09-14 10:15 ` Jan Beulich
2011-09-14 14:32 ` Konrad Rzeszutek Wilk
2011-09-14 15:01 ` [PATCH]: xen/blkback: Add support for old BARRIER requests - 'feature-barrier', was "Help with implementing some form of barriers in 3.0 kernels." Konrad Rzeszutek Wilk
2011-09-14 16:13 ` Jan Beulich
2011-09-15 12:51 ` Konrad Rzeszutek Wilk
2011-09-15 13:00 ` Jan Beulich
2011-09-15 14:21 ` Konrad Rzeszutek Wilk
2011-09-15 15:13 ` Jan Kara
2011-09-15 15:15 ` Christoph Hellwig
2011-09-16 9:24 ` Konrad Rzeszutek Wilk
2011-09-15 13:24 ` Jan Kara
2011-09-14 15:34 ` Help with implementing some form of barriers in 3.0 kernels Mike Snitzer
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