Re: [Qemu-devel] [PATCH 17/23] migration: make sure we always have a migration state

[Anthony Liguori <anthony@codemonkey.ws>]

On 09/23/2011 07:57 AM, Juan Quintela wrote:
> This cleans up a lot the code as we don't have to check anymore if
> the variable is NULL or not.
>
> We don't make it static, because when we integrate fault tolerance, we
> can have several migrations at once.
>
> Signed-off-by: Juan Quintela<quintela@redhat.com>
> ---
>   migration.c |  126 +++++++++++++++++++++++++---------------------------------
>   1 files changed, 54 insertions(+), 72 deletions(-)
>
> diff --git a/migration.c b/migration.c
> index 1cc21f0..c382383 100644
> --- a/migration.c
> +++ b/migration.c
> @@ -34,7 +34,13 @@
>   /* Migration speed throttling */
>   static int64_t max_throttle = (32<<  20);
>
> -static MigrationState *current_migration;
> +/* When we add fault tolerance, we could have several
> +   migrations at once.  For now we don't need to add
> +   dynamic creation of migration */
> +static MigrationState current_migration_static = {
> +    .state = MIG_STATE_NONE,
> +};
> +static MigrationState *current_migration =&current_migration_static;

This doesn't make sense to me.  We can have two migration states that are both 
in the MIG_STATE_NONE?  What does that actually mean?

I don't see the point in making migration state nullable via the state member 
other than avoiding the if (s == NULL) check.

Regards,

Anthony Liguori

>
>   static NotifierList migration_state_notifiers =
>       NOTIFIER_LIST_INITIALIZER(migration_state_notifiers);
> @@ -136,37 +142,34 @@ void do_info_migrate(Monitor *mon, QObject **ret_data)
>   {
>       QDict *qdict;
>
> -    if (current_migration) {
> -
> -        switch (current_migration->state) {
> -        case MIG_STATE_NONE:
> -            /* no migration has happened ever */
> -            break;
> -        case MIG_STATE_ACTIVE:
> -            qdict = qdict_new();
> -            qdict_put(qdict, "status", qstring_from_str("active"));
> -
> -            migrate_put_status(qdict, "ram", ram_bytes_transferred(),
> -                               ram_bytes_remaining(), ram_bytes_total());
> -
> -            if (blk_mig_active()) {
> -                migrate_put_status(qdict, "disk", blk_mig_bytes_transferred(),
> -                                   blk_mig_bytes_remaining(),
> -                                   blk_mig_bytes_total());
> -            }
> -
> -            *ret_data = QOBJECT(qdict);
> -            break;
> -        case MIG_STATE_COMPLETED:
> -            *ret_data = qobject_from_jsonf("{ 'status': 'completed' }");
> -            break;
> -        case MIG_STATE_ERROR:
> -            *ret_data = qobject_from_jsonf("{ 'status': 'failed' }");
> -            break;
> -        case MIG_STATE_CANCELLED:
> -            *ret_data = qobject_from_jsonf("{ 'status': 'cancelled' }");
> -            break;
> +    switch (current_migration->state) {
> +    case MIG_STATE_NONE:
> +        /* no migration has happened ever */
> +        break;
> +    case MIG_STATE_ACTIVE:
> +        qdict = qdict_new();
> +        qdict_put(qdict, "status", qstring_from_str("active"));
> +
> +        migrate_put_status(qdict, "ram", ram_bytes_transferred(),
> +                           ram_bytes_remaining(), ram_bytes_total());
> +
> +        if (blk_mig_active()) {
> +            migrate_put_status(qdict, "disk", blk_mig_bytes_transferred(),
> +                               blk_mig_bytes_remaining(),
> +                               blk_mig_bytes_total());
>           }
> +
> +        *ret_data = QOBJECT(qdict);
> +        break;
> +    case MIG_STATE_COMPLETED:
> +        *ret_data = qobject_from_jsonf("{ 'status': 'completed' }");
> +        break;
> +    case MIG_STATE_ERROR:
> +        *ret_data = qobject_from_jsonf("{ 'status': 'failed' }");
> +        break;
> +    case MIG_STATE_CANCELLED:
> +        *ret_data = qobject_from_jsonf("{ 'status': 'cancelled' }");
> +        break;
>       }
>   }
>
> @@ -357,11 +360,7 @@ void remove_migration_state_change_notifier(Notifier *notify)
>
>   int get_migration_state(void)
>   {
> -    if (current_migration) {
> -        return current_migration->state;
> -    } else {
> -        return MIG_STATE_ERROR;
> -    }
> +    return current_migration->state;
>   }
>
>   void migrate_fd_connect(MigrationState *s)
> @@ -386,28 +385,23 @@ void migrate_fd_connect(MigrationState *s)
>       migrate_fd_put_ready(s);
>   }
>
> -static MigrationState *migrate_create_state(Monitor *mon,
> -                                            int64_t bandwidth_limit,
> -                                            int detach, int blk, int inc)
> +static void migrate_init_state(Monitor *mon, int64_t bandwidth_limit,
> +                               int detach, int blk, int inc)
>   {
> -    MigrationState *s = g_malloc0(sizeof(*s));
> -
> -    s->blk = blk;
> -    s->shared = inc;
> -    s->mon = NULL;
> -    s->bandwidth_limit = bandwidth_limit;
> -    s->state = MIG_STATE_NONE;
> +    memset(current_migration, 0, sizeof(current_migration));
> +    current_migration->blk = blk;
> +    current_migration->shared = inc;
> +    current_migration->mon = NULL;
> +    current_migration->bandwidth_limit = bandwidth_limit;
> +    current_migration->state = MIG_STATE_NONE;
>
>       if (!detach) {
> -        migrate_fd_monitor_suspend(s, mon);
> +        migrate_fd_monitor_suspend(current_migration, mon);
>       }
> -
> -    return s;
>   }
>
>   int do_migrate(Monitor *mon, const QDict *qdict, QObject **ret_data)
>   {
> -    MigrationState *s = NULL;
>       const char *p;
>       int detach = qdict_get_try_bool(qdict, "detach", 0);
>       int blk = qdict_get_try_bool(qdict, "blk", 0);
> @@ -415,8 +409,7 @@ int do_migrate(Monitor *mon, const QDict *qdict, QObject **ret_data)
>       const char *uri = qdict_get_str(qdict, "uri");
>       int ret;
>
> -    if (current_migration&&
> -        current_migration->state == MIG_STATE_ACTIVE) {
> +    if (current_migration->state == MIG_STATE_ACTIVE) {
>           monitor_printf(mon, "migration already in progress\n");
>           return -1;
>       }
> @@ -425,43 +418,35 @@ int do_migrate(Monitor *mon, const QDict *qdict, QObject **ret_data)
>           return -1;
>       }
>
> -    s = migrate_create_state(mon, max_throttle, detach, blk, inc);
> +    migrate_init_state(mon, max_throttle, detach, blk, inc);
>
>       if (strstart(uri, "tcp:",&p)) {
> -        ret = tcp_start_outgoing_migration(s, p);
> +        ret = tcp_start_outgoing_migration(current_migration, p);
>   #if !defined(WIN32)
>       } else if (strstart(uri, "exec:",&p)) {
> -        ret = exec_start_outgoing_migration(s, p);
> +        ret = exec_start_outgoing_migration(current_migration, p);
>       } else if (strstart(uri, "unix:",&p)) {
> -        ret = unix_start_outgoing_migration(s, p);
> +        ret = unix_start_outgoing_migration(current_migration, p);
>       } else if (strstart(uri, "fd:",&p)) {
> -        ret = fd_start_outgoing_migration(s, p);
> +        ret = fd_start_outgoing_migration(current_migration, p);
>   #endif
>       } else {
>           monitor_printf(mon, "unknown migration protocol: %s\n", uri);
> -        ret  = -EINVAL;
> -        goto free_migrate_state;
> +        return -EINVAL;
>       }
>
>       if (ret<  0) {
>           monitor_printf(mon, "migration failed\n");
> -        goto free_migrate_state;
> +        return ret;
>       }
>
> -    g_free(current_migration);
> -    current_migration = s;
>       notifier_list_notify(&migration_state_notifiers, NULL);
>       return 0;
> -free_migrate_state:
> -    g_free(s);
> -    return -1;
>   }
>
>   int do_migrate_cancel(Monitor *mon, const QDict *qdict, QObject **ret_data)
>   {
> -    if (current_migration) {
> -        migrate_fd_cancel(current_migration);
> -    }
> +    migrate_fd_cancel(current_migration);
>       return 0;
>   }
>
> @@ -475,10 +460,7 @@ int do_migrate_set_speed(Monitor *mon, const QDict *qdict, QObject **ret_data)
>       }
>       max_throttle = d;
>
> -    if (current_migration) {
> -        qemu_file_set_rate_limit(current_migration->file, max_throttle);
> -    }
> -
> +    qemu_file_set_rate_limit(current_migration->file, max_throttle);
>       return 0;
>   }
>