Re: [PATCH] block: Error out on image creation with conflicting size options

[Eric Blake]

On 11/26/19 10:26 AM, Kevin Wolf wrote:

> > Actually, your patch fails to diagnose:
> >
> > $ qemu-img create -o size=1m,size=2m -f qcow2 x.qcow2
> > Formatting 'x.qcow2', fmt=qcow2 size=2097152 cluster_size=65536
> > lazy_refcounts=off refcount_bits=16
> >
> > so you may want to enhance this patch to also catch the case of -o size used
> > more than once.
>
> Hm... Isn't this something that QemuOpts should already catch? Or do we
> have callers that actually expect the same option specified multiple
> times?

QemuOpts is horrible.  It allows duplication, and leaves it up to the 
client what to do about it.  Some clients use the duplication to collect 
multiple arguments (such as specifying more than one cpu), some callers 
treat duplication by honoring only the FIRST option specified (and 
ignoring later uses - I find this ugly), and yet other callers treat 
duplication by honoring only the LAST option specified.

> Somehow I'm almost sure that Markus will know an example...

Probably of all three (ab)uses of QemuOpt duplication.

> But anyway, I figure the same problem exists for almost all options.
>
> Kevin

--
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org