WARNING - OLD ARCHIVES

This is an archived copy of the Xen.org mailing list, which we have preserved to ensure that existing links to archives are not broken. The live archive, which contains the latest emails, can be found at http://lists.xen.org/
   
 
 
Xen 
 
Home Products Support Community News
 
   
 

xen-devel

Re: [Xen-devel] RFC: Making QEMU honour 'readonly' flag for disks

To: "Daniel P. Berrange" <berrange@xxxxxxxxxx>
Subject: Re: [Xen-devel] RFC: Making QEMU honour 'readonly' flag for disks
From: Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>
Date: Wed, 30 Jul 2008 10:01:29 +0100
Cc: xen-devel@xxxxxxxxxxxxxxxxxxx
Delivery-date: Wed, 30 Jul 2008 02:33:15 -0700
Envelope-to: www-data@xxxxxxxxxxxxxxxxxxx
In-reply-to: <20080724113627.GU1138@xxxxxxxxxx>
List-help: <mailto:xen-devel-request@lists.xensource.com?subject=help>
List-id: Xen developer discussion <xen-devel.lists.xensource.com>
List-post: <mailto:xen-devel@lists.xensource.com>
List-subscribe: <http://lists.xensource.com/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=subscribe>
List-unsubscribe: <http://lists.xensource.com/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=unsubscribe>
Newsgroups: chiark.mail.xen.devel
References: <20080724113627.GU1138@xxxxxxxxxx> <18568.34189.57005.491667@xxxxxxxxxxxxxxxxxxxxxxxx>
Sender: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
Daniel P. Berrange writes ("[Xen-devel] RFC: Making QEMU honour 'readonly' flag 
for disks"):
> The Xen disk configuration syntax allows a block device to be marked as
> readonly, exclusive writable or shared writeable. The xen hotplug scripts
> will clash for clashing configs between domains, but  it is upto the
> backend drivers to actually enforce the readonly flag on I/O operations.
> The paravirt backend disk driver does this fine, but QEMU's emulated
> backend driver does not.

I still think this is a fix we should have but your patch is very
intrusive.  Is there some reason why you didn't just invent
BDRV_O_RDONLY_NO__ACTUALLY__READONLY ?  A new parameter to bdrv_new
seems quite wrong.

(It's a shame that the existing BDRV_O_RDONLY does something strange
and probably wrong, but we probably don't want to fix that in our
branch.)

Would you be willing to prepare a revised patch along those lines ?
If you don't want to deal with upstream I can put your change in the
pile with the others ...

Ian.

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel