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

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

* Zhang Chen (zhangckid@gmail.com) wrote:
> On Tue, Aug 7, 2018 at 10:30 PM Dr. David Alan Gilbert <dgilbert@redhat.com>
> wrote:
> 
> > * 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.
> > >
> > > 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;
> > > +    }
> >
> > 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.

OK, it might be worth clarifying the docs.

Dave

> 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 / dgilbert@redhat.com / Manchester, UK
> >
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK