Re: [Qemu-devel] [PATCH V3 7/7] Migration/colo.c: Make user obtain the COLO mode info after failover

[Dr. David Alan Gilbert]

* Zhang, Chen (address@hidden) wrote:
> 
> 
> 
> -----Original Message-----
> From: Dr. David Alan Gilbert [mailto:address@hidden 
> Sent: Saturday, March 9, 2019 1:46 AM
> To: Zhang, Chen <address@hidden>
> Cc: Li Zhijian <address@hidden>; Zhang Chen <address@hidden>; Juan Quintela 
> <address@hidden>; zhanghailiang <address@hidden>; Markus Armbruster 
> <address@hidden>; Eric Blake <address@hidden>; qemu-dev <address@hidden>
> Subject: Re: [PATCH V3 7/7] Migration/colo.c: Make user obtain the COLO mode 
> info after failover
> 
> * Zhang Chen (address@hidden) wrote:
> > From: Zhang Chen <address@hidden>
> > 
> > Add the last_colo_mode to save the status after failover.
> > This patch can solve the issue that user got nothing to call 
> > query_colo_status after failover.
> 
> I don't understand what this is doing; cna you show me an example of the way 
> the state looks before and after the patch?
> 
> Sure.
> In current codes, when we use the " query_colo_status "  after failover, the 
> mode field will always return "none".
> Because after failover we can't use  " get_colo_mode()" to get the mode, we 
> need the last_colo_mode args to save the last state.
> I think we will use this args in new colo feature development.

But, after a fail-over, 'none' is correct isn't it?  There's no colo
protection any more, so it's wrong to say that the VM is either a
primary or a secondary.

Dave

> Thanks
> Zhang Chen
> 
> Dave
> 
> > Signed-off-by: Zhang Chen <address@hidden>
> > ---
> >  migration/colo.c | 28 +++++++++++++++++++++++-----
> >  1 file changed, 23 insertions(+), 5 deletions(-)
> > 
> > diff --git a/migration/colo.c b/migration/colo.c index 
> > d1ae2e6d11..6eba8e06f2 100644
> > --- a/migration/colo.c
> > +++ b/migration/colo.c
> > @@ -38,6 +38,9 @@
> >  static bool vmstate_loading;
> >  static Notifier packets_compare_notifier;
> >  
> > +/* User need to know colo mode after COLO failover */ static COLOMode 
> > +last_colo_mode;
> > +
> >  #define COLO_BUFFER_BASE_SIZE (4 * 1024 * 1024)
> >  
> >  bool migration_in_colo_state(void)
> > @@ -197,7 +200,10 @@ void colo_do_failover(MigrationState *s)
> >          vm_stop_force_state(RUN_STATE_COLO);
> >      }
> >  
> > -    switch (get_colo_mode()) {
> > +    /* Update last_COLO_mode to avoid unexpectedly exit COLO status */
> > +    last_colo_mode = get_colo_mode();
> > +
> > +    switch (last_colo_mode) {
> >      case COLO_MODE_PRIMARY:
> >          primary_vm_do_failover();
> >          break;
> > @@ -263,7 +269,7 @@ COLOStatus *qmp_query_colo_status(Error **errp)  {
> >      COLOStatus *s = g_new0(COLOStatus, 1);
> >  
> > -    s->mode = get_colo_mode();
> > +    s->mode = last_colo_mode;
> >  
> >      switch (failover_get_state()) {
> >      case FAILOVER_STATUS_NONE:
> > @@ -515,6 +521,12 @@ static void colo_process_checkpoint(MigrationState *s)
> >      Error *local_err = NULL;
> >      int ret;
> >  
> > +    last_colo_mode = get_colo_mode();
> > +    if (last_colo_mode != COLO_MODE_PRIMARY) {
> > +        error_report("COLO mode must be COLO_MODE_PRIMARY");
> > +        return;
> > +    }
> > +
> >      failover_init_state();
> >  
> >      s->rp_state.from_dst_file = 
> > qemu_file_get_return_path(s->to_dst_file);
> > @@ -682,12 +694,18 @@ void *colo_process_incoming_thread(void *opaque)
> >      Error *local_err = NULL;
> >      int ret;
> >  
> > -    rcu_register_thread();
> > -    qemu_sem_init(&mis->colo_incoming_sem, 0);
> > -
> >      migrate_set_state(&mis->state, MIGRATION_STATUS_ACTIVE,
> >                        MIGRATION_STATUS_COLO);
> >  
> > +    last_colo_mode = get_colo_mode();
> > +    if (last_colo_mode != COLO_MODE_SECONDARY) {
> > +        error_report("COLO mode must be COLO_MODE_SECONDARY");
> > +        return NULL;
> > +    }
> > +
> > +    rcu_register_thread();
> > +    qemu_sem_init(&mis->colo_incoming_sem, 0);
> > +
> >      failover_init_state();
> >  
> >      mis->to_src_file = qemu_file_get_return_path(mis->from_src_file);
> > --
> > 2.17.GIT
> > 
> --
> Dr. David Alan Gilbert / address@hidden / Manchester, UK
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK