[Qemu-devel] Re: [RFC][STABLE 0.13] Revert "qcow2: Use bdrv_(p)write_sync for metadata writes"

[Avi Kivity]

 On 08/24/2010 04:40 PM, Anthony Liguori wrote:
> > 1. Allocate a cluster (increase refcount table)
> >
> > 2. Link cluster to L2 table
> >
> > 3. Second operation makes it to disk; first still in pagecache
> >
> > 4. Crash
> >
> > 5. Dangling pointer from L2 to freed cluster
>
>
> Yes, having this discussion in IRC.
>
> The problem is that we maintain a refcount table. 

Are you sure that's the only issue?

> If we didn't do internal disk snapshots, we wouldn't have this 
> problem.  IOW, VMDK doesn't have this problem so the answer to my very 
> first question is that qcow2 is too difficult a format to get right.

One doesn't follow from the other (though I'm no fan of internal 
snapshots, myself).

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error compiling committee.c: too many arguments to function