Re: [Qemu-devel] [PATCH] migration: re-active images when migration fails to complete

[Hailiang Zhang <zhang.zhanghailiang@huawei.com>]

Cc: qemu-stable@nongnu.org

On 2016/11/19 19:43, zhanghailiang wrote:
> commit fe904ea8242cbae2d7e69c052c754b8f5f1ba1d6 fixed a case
> which migration aborted QEMU because it didn't regain the control
> of images while some errors happened.
>
> Actually, we have another case in that error path to abort QEMU
> because of the same reason:
>      migration_thread()
>          migration_completion()
>             bdrv_inactivate_all() ----------------> inactivate images
>             qemu_savevm_state_complete_precopy()
>                 socket_writev_buffer() --------> error because destination fails
>               qemu_fflush() -------------------> set error on migration stream
>             qemu_mutex_unlock_iothread() ------> unlock
>      qmp_migrate_cancel() ---------------------> user cancelled migration
>          migrate_set_state() ------------------> set migrate CANCELLING
>      migration_completion() -----------------> go on to fail_invalidate
>          if (s->state == MIGRATION_STATUS_ACTIVE) -> Jump this branch
>      migration_thread() -----------------------> break migration loop
>        vm_start() -----------------------------> restart guest with inactive
>                                                  images
> We failed to regain the control of images because we only regain it
> while the migration state is "active", but here users cancelled the migration
> when they found some errors happened (for example, libvirtd daemon is shutdown
> in destination unexpectedly).
>
> Signed-off-by: zhanghailiang <zhang.zhanghailiang@huawei.com>
> ---
>   migration/migration.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/migration/migration.c b/migration/migration.c
> index f498ab8..0c1ee6d 100644
> --- a/migration/migration.c
> +++ b/migration/migration.c
> @@ -1752,7 +1752,8 @@ fail_invalidate:
>       /* If not doing postcopy, vm_start() will be called: let's regain
>        * control on images.
>        */
> -    if (s->state == MIGRATION_STATUS_ACTIVE) {
> +    if (s->state == MIGRATION_STATUS_ACTIVE ||
> +        s->state == MIGRATION_STATUS_CANCELLING) {
>           Error *local_err = NULL;
>
>           bdrv_invalidate_cache_all(&local_err);
>