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

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

On 2016/5/6 17:09, Changlong Xie wrote:
> 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 <zhang.zhanghailiang@huawei.com>
>> Signed-off-by: Li Zhijian <lizhijian@cn.fujitsu.com>
>> Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
>> ---
>> 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.
>

Good catch, i will fix them all in next version, thanks.

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