Re: Re: [PATCH] Fix restore handling checks

[Michal Novotny <minovotn@redhat.com>]

On 06/23/2010 02:35 PM, Alan Cox wrote:
> On Wed, 23 Jun 2010 13:29:56 +0200
> Michal Novotny<minovotn@redhat.com>  wrote:
>
>    
>> On 06/23/2010 01:27 PM, Ian Jackson wrote:
>>      
>>> Paolo Bonzini writes ("Re: [PATCH] Fix restore handling checks"):
>>>
>>>        
>>>> We tried to get that to work, and we could not really find a device
>>>> error that worked reliably in the guests.  We often got infinite loops
>>>> on mount or little after that, on both Linux and Windows.
>>>>
>>>>          
>>> That's fine.  If the admins don't want that then they can use SCSI or
>>> PV or simply not tell the guest to write to the device.
>>>
>>> Disallowing the configuration entirely just because the error handling
>>> is suboptimal (but safe!) is not correct.
>>>
>>> Ian.
>>>
>>>        
>> Why do you think so, Ian? This follows the IDE specifications to
>> disallow read-only IDE disks since the specs doesn't support IDE
>> read-only disks. The only read-only device being supported by IDE specs
>> is the CD-ROM device.
>>      
> IDE (or more properly ATA) doesn't support CD-ROM either. ATAPI does, and
> it also supports other ATAPI devices with write protect including magneto
> optical and floppy.
>
>
>    

Agreed Alan. This is right that ATAPI does. Nevertheless in IDE specs 
it's about ATA and ATAPI. The read-only file systems are supported for 
IDE drives only for floppy and tape media according to the linux kernel 
source codes. Also, CD-ROM devices can be read-only but no other IDE 
media, i.e. no IDE disks.

Michal

-- 
Michal Novotny<minovotn@redhat.com>, RHCE
Virtualization Team (xen userspace), Red Hat