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Date: Mon, 27 Aug 2007 23:37:48 +0300
From: Avi Kivity <avi@qumranet.com>
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Subject: Re: [Qemu-devel] Re: [et-mgmt-tools] Image Corruption Possible with
	qemu and qemu-kvm
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To: "Daniel P. Berrange" <berrange@redhat.com>, qemu-devel@nongnu.org
Cc: Fedora/Linux Management Tools <et-mgmt-tools@redhat.com>

Daniel P. Berrange wrote:
> On Mon, Aug 27, 2007 at 10:19:42PM +0200, Sven Oehme wrote:
>   
>> i thought it might be good to post this on qemu-devel as well, as i see 
>> this as a general qemu / kvm / xen /whatevercomesnext issue .
>>
>> are there any plans to implement a default in qemu to prevent accessing 
>> the same image multiple times ? 
>>     
>
> Each QEMU instance is unware of each other so can't directly check this. One
> possiblity would be for QEMU to use fcntl() to take a lock on a disk image
> when opening it. With raw disk images at least, it is, however, safe to let
> multiple QEMU instances use it at once *provided* you have a clustered
> filesystem installed, rather than regular FAT or ext2/3, so one wouldn't want
> to exclude this use case.
>   

Yes, taking an advisory lock is a good idea, provided there is an option 
to override it.

I've killed a few images myself...

-- 
Any sufficiently difficult bug is indistinguishable from a feature.