Re: [Qemu-devel] [PATCH V7 RESEND 05/17] COLO: Add block replication into colo process

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Zhang Chen (zhangckid@gmail.com) wrote:
> Make sure master start block replication after slave's block
> replication started.
> 
> Besides, we need to activate VM's blocks before goes into
> COLO state.

Stefan: This looks mostly OK to me, how does it look from the block
side?

The only thing I'd like to be convinced of is that
the replication_do_checkpoint_all() is synchronous enough
to know that the destination has received all disk IO
for one checkpoint before the primary starts running the next one.

Also, in the 'colo_do_checkpoint_transaction' the replication is called
near the start; is that the right point or should it be after any of the
device saves (could they spit out one last write?)

Dave

> Signed-off-by: zhanghailiang <zhang.zhanghailiang@huawei.com>
> Signed-off-by: Li Zhijian <lizhijian@cn.fujitsu.com>
> Signed-off-by: Zhang Chen <zhangckid@gmail.com>
> ---
>  migration/colo.c      | 43 +++++++++++++++++++++++++++++++++++++++++++
>  migration/migration.c |  9 +++++++++
>  2 files changed, 52 insertions(+)
> 
> diff --git a/migration/colo.c b/migration/colo.c
> index 081df1835f..e06640c3d6 100644
> --- a/migration/colo.c
> +++ b/migration/colo.c
> @@ -27,6 +27,7 @@
>  #include "replication.h"
>  #include "net/colo-compare.h"
>  #include "net/colo.h"
> +#include "block/block.h"
>  
>  static bool vmstate_loading;
>  static Notifier packets_compare_notifier;
> @@ -56,6 +57,7 @@ static void secondary_vm_do_failover(void)
>  {
>      int old_state;
>      MigrationIncomingState *mis = migration_incoming_get_current();
> +    Error *local_err = NULL;
>  
>      /* Can not do failover during the process of VM's loading VMstate, Or
>       * it will break the secondary VM.
> @@ -73,6 +75,11 @@ static void secondary_vm_do_failover(void)
>      migrate_set_state(&mis->state, MIGRATION_STATUS_COLO,
>                        MIGRATION_STATUS_COMPLETED);
>  
> +    replication_stop_all(true, &local_err);
> +    if (local_err) {
> +        error_report_err(local_err);
> +    }
> +
>      if (!autostart) {
>          error_report("\"-S\" qemu option will be ignored in secondary side");
>          /* recover runstate to normal migration finish state */
> @@ -110,6 +117,7 @@ static void primary_vm_do_failover(void)
>  {
>      MigrationState *s = migrate_get_current();
>      int old_state;
> +    Error *local_err = NULL;
>  
>      migrate_set_state(&s->state, MIGRATION_STATUS_COLO,
>                        MIGRATION_STATUS_COMPLETED);
> @@ -133,6 +141,13 @@ static void primary_vm_do_failover(void)
>                       FailoverStatus_str(old_state));
>          return;
>      }
> +
> +    replication_stop_all(true, &local_err);
> +    if (local_err) {
> +        error_report_err(local_err);
> +        local_err = NULL;
> +    }
> +
>      /* Notify COLO thread that failover work is finished */
>      qemu_sem_post(&s->colo_exit_sem);
>  }
> @@ -356,6 +371,11 @@ static int colo_do_checkpoint_transaction(MigrationState *s,
>      qemu_savevm_state_header(fb);
>      qemu_savevm_state_setup(fb);
>      qemu_mutex_lock_iothread();
> +    replication_do_checkpoint_all(&local_err);
> +    if (local_err) {
> +        qemu_mutex_unlock_iothread();
> +        goto out;
> +    }
>      qemu_savevm_state_complete_precopy(fb, false, false);
>      qemu_mutex_unlock_iothread();
>  
> @@ -446,6 +466,12 @@ static void colo_process_checkpoint(MigrationState *s)
>      object_unref(OBJECT(bioc));
>  
>      qemu_mutex_lock_iothread();
> +    replication_start_all(REPLICATION_MODE_PRIMARY, &local_err);
> +    if (local_err) {
> +        qemu_mutex_unlock_iothread();
> +        goto out;
> +    }
> +
>      vm_start();
>      qemu_mutex_unlock_iothread();
>      trace_colo_vm_state_change("stop", "run");
> @@ -585,6 +611,11 @@ void *colo_process_incoming_thread(void *opaque)
>      object_unref(OBJECT(bioc));
>  
>      qemu_mutex_lock_iothread();
> +    replication_start_all(REPLICATION_MODE_SECONDARY, &local_err);
> +    if (local_err) {
> +        qemu_mutex_unlock_iothread();
> +        goto out;
> +    }
>      vm_start();
>      trace_colo_vm_state_change("stop", "run");
>      qemu_mutex_unlock_iothread();
> @@ -665,6 +696,18 @@ void *colo_process_incoming_thread(void *opaque)
>              goto out;
>          }
>  
> +        replication_get_error_all(&local_err);
> +        if (local_err) {
> +            qemu_mutex_unlock_iothread();
> +            goto out;
> +        }
> +        /* discard colo disk buffer */
> +        replication_do_checkpoint_all(&local_err);
> +        if (local_err) {
> +            qemu_mutex_unlock_iothread();
> +            goto out;
> +        }
> +
>          vmstate_loading = false;
>          vm_start();
>          trace_colo_vm_state_change("stop", "run");
> diff --git a/migration/migration.c b/migration/migration.c
> index bca187275a..ddd0c4b988 100644
> --- a/migration/migration.c
> +++ b/migration/migration.c
> @@ -357,6 +357,7 @@ static void process_incoming_migration_co(void *opaque)
>      MigrationIncomingState *mis = migration_incoming_get_current();
>      PostcopyState ps;
>      int ret;
> +    Error *local_err = NULL;
>  
>      assert(mis->from_src_file);
>      mis->largest_page_size = qemu_ram_pagesize_largest();
> @@ -388,6 +389,14 @@ static void process_incoming_migration_co(void *opaque)
>  
>      /* we get COLO info, and know if we are in COLO mode */
>      if (!ret && migration_incoming_enable_colo()) {
> +        /* Make sure all file formats flush their mutable metadata */
> +        bdrv_invalidate_cache_all(&local_err);
> +        if (local_err) {
> +            migrate_set_state(&mis->state, MIGRATION_STATUS_ACTIVE,
> +                    MIGRATION_STATUS_FAILED);
> +            error_report_err(local_err);
> +            exit(EXIT_FAILURE);
> +        }
>          mis->migration_incoming_co = qemu_coroutine_self();
>          qemu_thread_create(&mis->colo_incoming_thread, "COLO incoming",
>               colo_process_incoming_thread, mis, QEMU_THREAD_JOINABLE);
> -- 
> 2.17.0
> 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK