From mboxrd@z Thu Jan  1 00:00:00 1970
From: Ian Campbell <Ian.Campbell@citrix.com>
Subject: Re: [PATCH v2] introduce a cache options for PV disks
Date: Thu, 27 Jun 2013 17:58:51 +0100
Message-ID: <1372352331.8976.51.camel@zakaz.uk.xensource.com>
References: <alpine.DEB.2.02.1306271238100.4782@kaball.uk.xensource.com>
	<20940.19076.523978.4704@mariner.uk.xensource.com>
	<20940.25537.183890.394352@mariner.uk.xensource.com>
	<1372350299.8976.26.camel@zakaz.uk.xensource.com>
	<20940.26810.227963.193621@mariner.uk.xensource.com>
	<20940.27003.695837.65658@mariner.uk.xensource.com>
	<1372351312.8976.44.camel@zakaz.uk.xensource.com>
	<20940.28013.656000.329381@mariner.uk.xensource.com>
Mime-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit
Return-path: <xen-devel-bounces@lists.xen.org>
In-Reply-To: <20940.28013.656000.329381@mariner.uk.xensource.com>
List-Unsubscribe: <http://lists.xen.org/cgi-bin/mailman/options/xen-devel>,
	<mailto:xen-devel-request@lists.xen.org?subject=unsubscribe>
List-Post: <mailto:xen-devel@lists.xen.org>
List-Help: <mailto:xen-devel-request@lists.xen.org?subject=help>
List-Subscribe: <http://lists.xen.org/cgi-bin/mailman/listinfo/xen-devel>,
	<mailto:xen-devel-request@lists.xen.org?subject=subscribe>
Sender: xen-devel-bounces@lists.xen.org
Errors-To: xen-devel-bounces@lists.xen.org
To: Ian Jackson <Ian.Jackson@eu.citrix.com>
Cc: xen-devel@lists.xensource.com, Stefano Stabellini <stefano.stabellini@eu.citrix.com>
List-Id: xen-devel@lists.xenproject.org

On Thu, 2013-06-27 at 17:50 +0100, Ian Jackson wrote:
> Ian Campbell writes ("Re: [PATCH v2] introduce a cache options for PV disks"):
> > I think I can parse it now. It doesn't really say what the option does
> > though. I'd expect it to say something about "disabling the workaround"
> > or "the backend may use O_DIRECT".
> 
> How about:

Sounds good thanks.

> 
>  * direct-io-safe
>  *      Values:         0/1 (boolean)
>  *      Default Value:  0
>  *
>  *      The underlying storage is not affected by the direct IO memory
>  *      lifetime bug.  See:
>  *        http://lists.xen.org/archives/html/xen-devel/2012-12/msg01154.html
>  *
>  *      Therefore this option gives the backend permission to use
>  *      O_DIRECT, notwithstanding that bug.
>  *
>  *      That is, if this option is enabled, use of O_DIRECT is safe,
>  *      in circumstances where we would normally have avoided it as a
>  *      workaround for that bug.  This option is not relevant for all
>  *      backends, and even not necessarily supported for those for
>  *      which it is relevant.  A backend which knows that it is not
>  *      affected by the bug can ignore this option.
>  *
>  *      This option doesn't require a backend to use O_DIRECT, so it
>  *      should not be used to try to control the caching behaviour.
> 
> Ian.