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Re: [libvirt] [PATCH] Fix up basic migration.



On 05/21/2010 07:22 AM, Chris Lalancette wrote:
>>> -    virCheckFlags(VIR_MIGRATE_NON_SHARED_DISK | VIR_MIGRATE_NON_SHARED_INC,
>>> -                  -1);
>>> -
>>
>> Why are you removing the valid flag check altogether?  Is it a matter of
>> adding more valid flags, or is this just a forwarding routine to other
>> methods that also do a valid flag check?
> 
> Yeah, I guess I should have been a bit more explicit here.  There's no hard-and-fast
> rules about virCheckFlags(), but the general usage of it seems to be directly at
> the entry points to the driver (i.e. in qemuDomainSuspend(), etc).  doNativeMigrate()
> is not an entry point, it is a helper function.  In addition, there is a long list
> of flags that migration supports, so the above list is far from complete.  Would it
> be better if I added the check to qemuDomainMigratePerform() (with the complete
> list of flags), which is actually the entry point for this function?

Sounds good to me - if all entry points filter on all accepted flags,
then helper functions can assume that flags are already valid.  As long
as the filtering gets done somewhere, we've left the door open for
adding future flags while still correctly identifying situations where
we are talking to older implementations that can't honor new flags.
It's only when there is no flag filtering at all that we've locked
ourselves out of easy-to-validate future extensions.

-- 
Eric Blake   eblake redhat com    +1-801-349-2682
Libvirt virtualization library http://libvirt.org

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