Re: [Qemu-devel] [PATCH COLO-Frame v16 23/35] COLO failover: Don't do failover during loading VM's state

[Changlong Xie]

On 04/08/2016 02:26 PM, zhanghailiang wrote:
> We should not do failover work while the main thread is loading
> VM's state, otherwise it will destroy the consistent of VM's memory and
> device state.
>
> Here we add a new failover status 'RELAUNCH' which means we should
> relaunch the process of failover.
>
> Signed-off-by: zhanghailiang <address@hidden>
> Signed-off-by: Li Zhijian <address@hidden>
> Reviewed-by: Dr. David Alan Gilbert <address@hidden>
> ---
> v14:
> - Move the place of 'vmstate_loading = false;'.
> v13:
> - Add Reviewed-by tag
> ---
>   include/migration/failover.h |  2 ++
>   migration/colo.c             | 25 +++++++++++++++++++++++++
>   2 files changed, 27 insertions(+)
>
> diff --git a/include/migration/failover.h b/include/migration/failover.h
> index c4bd81e..99b0d58 100644
> --- a/include/migration/failover.h
> +++ b/include/migration/failover.h
> @@ -20,6 +20,8 @@ typedef enum COLOFailoverStatus {
>       FAILOVER_STATUS_REQUEST = 1, /* Request but not handled */
>       FAILOVER_STATUS_HANDLING = 2, /* In the process of handling failover */
>       FAILOVER_STATUS_COMPLETED = 3, /* Finish the failover process */
> +    /* Optional, Relaunch the failover process, again 'NONE' -> 'COMPLETED' */
> +    FAILOVER_STATUS_RELAUNCH = 4,
>   } COLOFailoverStatus;
>
>   void failover_init_state(void);
> diff --git a/migration/colo.c b/migration/colo.c
> index c4989c6..252a290 100644
> --- a/migration/colo.c
> +++ b/migration/colo.c
> @@ -20,6 +20,8 @@
>   #include "migration/failover.h"
>   #include "qapi-event.h"
>
> +static bool vmstate_loading;
> +
>   /* colo buffer */
>   #define COLO_BUFFER_BASE_SIZE (4 * 1024 * 1024)
>
> @@ -52,6 +54,19 @@ static void secondary_vm_do_failover(void)
>       int old_state;
>       MigrationIncomingState *mis = migration_incoming_get_current();
>
> +    /* Can not do failover during the process of VM's loading VMstate, Or
> +      * it will break the secondary VM.

Wrong comments style

> +      */
> +    if (vmstate_loading) {
> +        old_state = failover_set_state(FAILOVER_STATUS_HANDLING,
> +                                       FAILOVER_STATUS_RELAUNCH);
> +        if (old_state != FAILOVER_STATUS_HANDLING) {
> +            error_report("Unknown error while do failover for secondary VM,"
> +                         "old_state: %d", old_state);
> +        }
> +        return;
> +    }
> +
>       migrate_set_state(&mis->state, MIGRATION_STATUS_COLO,
>                         MIGRATION_STATUS_COMPLETED);
>
> @@ -561,13 +576,22 @@ void *colo_process_incoming_thread(void *opaque)
>
>           qemu_mutex_lock_iothread();
>           qemu_system_reset(VMRESET_SILENT);
> +        vmstate_loading = true;
>           if (qemu_loadvm_state(fb) < 0) {
>               error_report("COLO: loadvm failed");
>               qemu_mutex_unlock_iothread();
>               goto out;
>           }
> +
> +        vmstate_loading = false;
>           qemu_mutex_unlock_iothread();
>
> +        if (failover_get_state() == FAILOVER_STATUS_RELAUNCH) {
> +            failover_set_state(FAILOVER_STATUS_RELAUNCH, FAILOVER_STATUS_NONE);
> +            failover_request_active(NULL);
> +            goto out;
> +        }
> +
>           colo_send_message(mis->to_src_file, COLO_MESSAGE_VMSTATE_LOADED,
>                        &local_err);
>           if (local_err) {
> @@ -579,6 +603,7 @@ void *colo_process_incoming_thread(void *opaque)
>       }
>
>   out:
> +     vmstate_loading = false;

An redundant blank.

It seems there are many coding style issues in whole colo.c that you 
did't notice.

Thanks
        -Xie

>       /* Throw the unreported error message after exited from loop */
>       if (local_err) {
>           error_report_err(local_err);