On Tue, Sep 20, 2016 at 09:40:22 -0400, Corey S. McQuay wrote:
Currently Libvirt allows attempts to migrate read only disks. Qemu cannot handle this as read only disks cannot be written to on the destination system. The end result is a cryptic error message and a failed migration.
This is not necessarily true. Read only disks can sometimes be in fact backed by storage that is writable and it's desired to be migrated. I think you want to specify which storage to migrate using the VIR_MIGRATE_PARAM_MIGRATE_DISKS migration parameter for virDomainMigrate3. http://libvirt.org/html/libvirt-libvirt-domain.html#virDomainMigrate3 http://libvirt.org/html/libvirt-libvirt-domain.html#VIR_MIGRATE_PARAM_MIGRAT... Virsh also implements support for that flag.
This patch causes migration to fail earlier and provides a meaningful error message stating that migrating read only disks is not supported.
Signed-off-by: Corey S. McQuay <csmcquay@linux.vnet.ibm.com> Reviewed-by: Jason J. Herne <jjherne@linux.vnet.ibm.com> Reviewed-by: Boris Fiuczynski <fiuczy@linux.vnet.ibm.com> --- src/qemu/qemu_migration.c | 7 +++++++ 1 file changed, 7 insertions(+)
diff --git a/src/qemu/qemu_migration.c b/src/qemu/qemu_migration.c index e451ef6..011f349 100644 --- a/src/qemu/qemu_migration.c +++ b/src/qemu/qemu_migration.c @@ -2157,6 +2157,13 @@ qemuMigrationDriveMirror(virQEMUDriverPtr driver, if (!qemuMigrateDisk(disk, nmigrate_disks, migrate_disks)) continue;
+ if (disk->src->readonly) { + virReportError(VIR_ERR_OPERATION_UNSUPPORTED, + _("Cannot migrate read-only disk %s"), + disk->dst); + goto cleanup; + }
NACK this would break the above use case. You want to specify explicitly which storage to migrate using the above described API. Peter