Re: [libvirt] [PATCH] qemu: fix migration with local and VIR_STORAGE_TYPE_NETWORK disks

On 02/07/2018 12:05 PM, Daniel P. Berrangé wrote: > On Wed, Feb 07, 2018 at 11:57:19AM -0600, Chris Friesen wrote: > > In the current implementation of qemuMigrateDisk() the value of the > > "nmigrate_disks" parameter wrongly impacts the decision whether or not > > to migrate a disk that is not a member of "migrate_disks": > > > > 1) If "nmigrate_disks" is zero, "disk" is migrated if it's non-shared > > non-readonly with source. > > > > 2) If "nmigrate_disks" is non-zero and "disk" is not a member of > > "migrate_disks" then "disk" is not migrated. This should instead proceed > > with checking conditions as per 1) and allow migration of non-shared > > non-readonly disks with source. > > Huh, this doesn't make sense. If an app has passed a list of disks > in migrate_disks, we must *never* touch any disk that is not present > in this list. If the app wanted the other disk(s) migrated, it would > have included it in the list of disks it passed in. Okay, that makes sense. I can restore the "return false" here. Are you okay with the other change?

Our original problem scenario was where the root disk is rbd and there is a read-only ISO config-drive, and "nmigrate_disks" is zero. What we see in this case is that qemuMigrateDisk() returns "true" for the rbd disk, which then causes qemuMigrationPrecreateStorage() to fail with "pre-creation of storage targets for incremental storage migration is not supported".