Re: [libvirt] [PATCH v13] support offline migration

On 11/08/2012 08:54 PM, li guang wrote: > 在 2012-11-08四的 20:28 -0700，Eric Blake写道： >> On 11/08/2012 07:57 PM, li guang wrote: >>>> What if you want to offline migrate a domain that is currently running? >>>> I think it's better to first move qemuDomainCheckEjectableMedia down to >>>> qemuMigrationBegin in a separate patch and then just use the code from >>>> v12 (without using the offline label). >>> >>> sorry, I don't like to do offline migrate for a domain that's running. >> >> Why not, when we've already argued it can be useful? You don't have to >> support it in the same patch, but you should at least take the advice on >> how to refactor things so that someone else that does like the idea can >> extend things to provide it. There's nothing wrong with having >> persistent definitions of the same domain on more than one machine, as >> long as only one machine at a time is running it; and after all, with >> live migration, if you _don't_ pass the --undefinesource flag, you will >> be left in the same situation where a persistent domain on the source is >> left behind even when the running domain has migrated. > > I mean we should do this explicitly, e.g. an flag to notify us we are > doing job for active domain by walking through offline path. > I said this before, at comment on virsh change. You ARE being explicit when you say 'virsh migrate --offline'. If the domain is transient, it must fail, but if the domain is persistent, then whether or not it is running, you are requesting that ONLY the offline state be migrated.

>>> >>> without this how do you know you a offline migration at target side? >> >> By the presence or absence of the flag. If the flag is present, you are > > seem flags was forgotten at qemuDomainMigratePrepare3, so any > preparation for offline migration will be impossible, isn't it? > do you mean I should change MigratePrepare functions to add > flags as a parameter? Huh? qemuDomainMigratePrepare3 already has a flags argument (arg 8), and it is directly related to the flags argument that was originally passed to virDomainMigrate() in libvirt.c.