On 03/19/2012 10:18 AM, Jiri Denemark wrote:
Destination daemon should not rely on the client or source daemon (depending on the type of migration) to call Finish when migration fails, because the client may crash before it can do so. The domain prepared for incoming migration is set to be destroyed (and migration job cleaned up) when connection with the client closes but this is not enough. If the associated qemu process crashes after Prepare step and the domain is cleaned up before the connection gets closed, autodestroy is not called for the domain and migration jobs remains set. In case the domain is defined on destination host (i.e., it is not completely removed once destroyed) we keep the job set for ever. To fix this, we register a cleanup callback which is responsible to clean migration-in job when a domain dies anywhere between Prepare and Finish steps. Note that we can't blindly clean any job when spotting EOF on monitor since normally an API is running at that time. --- src/qemu/qemu_domain.c | 2 -- src/qemu/qemu_domain.h | 2 ++ src/qemu/qemu_migration.c | 22 ++++++++++++++++++++++ 3 files changed, 24 insertions(+), 2 deletions(-)
I'm restating my understanding of the bug, to make sure I am sure why your patch helps: - src requests a migration - dest starts a qemu process using information from the src, but the destination happens to be running an older qemu that can't support the full migration - qemu dies, but the destination hasn't seen a 'Finish' from the source, so the job remains open and the domain remains - connection is broken, but the open job prevents reclaiming the autodestroy domain on the destination - new connection is made, but source can't migrate because destination is already locked up on the stale attempt and the fix is adding a new callback, which says if qemu dies while the callback is registered, we cancel the migration job; therefore, even without a 'Finish' from the source, the autodestroy can now kick in ACK. -- Eric Blake eblake@redhat.com +1-919-301-3266 Libvirt virtualization library http://libvirt.org