Re: [Qemu-devel] [PATCH V10 05/20] COLO: Add block replication into colo process

[Zhang Chen]

On Tue, Aug 7, 2018 at 10:30 PM Dr. David Alan Gilbert <address@hidden>
wrote:

> * Zhang Chen (address@hidden) 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.
> >
> > Signed-off-by: zhanghailiang <address@hidden>
> > Signed-off-by: Li Zhijian <address@hidden>
> > Signed-off-by: Zhang Chen <address@hidden>
> > ---
> >  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;
> > +    }
>
> In docs/block-replication.txt it says:
>   b. replication_do_checkpoint_all()
>    This interface is called after all VM state is transferred to
>    Secondary QEMU. The Disk buffer will be dropped in this interface.
>    The caller must hold the I/O mutex lock if it is in migration/checkpoint
>    thread.
>
> but we're making this call before the call below that actually transfers
> all the state.  Which is right?
>

Hi Dave,

The "docs/block-replication.txt" means we should call the
replication_do_checkpoint_all() after VM state is transferred in secondary
node,
and in primary node this function no need to call before transfers all the
state.

Thanks
Zhang Chen



>
> Other than that I think it's OK.
>
> Dave
>
> >      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 ce06941706..c97b7660af 100644
> > --- a/migration/migration.c
> > +++ b/migration/migration.c
> > @@ -385,6 +385,7 @@ 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();
> > @@ -416,6 +417,14 @@ 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);
> > --
> > 2.17.1
> >
> --
> Dr. David Alan Gilbert / address@hidden / Manchester, UK
>