On Fri, Dec 26, 2025 at 06:19:15PM -0300, Fabiano Rosas wrote:
> Simplify migration_channel_connect() and migration_connect() to not
> take an error as input. Move the error handling into the paths that
> generate the error.
> 
> To achive this, call migration_connect_error_propagate() from socket.c
> and tls.c, which are the async paths.
> 
> For the sync paths, the handling is done as normal by returning all
> the way to qmp_migrate_finish(), except that now the sync paths don't
> pass the error forward into migration_connect() anymore.
> 
> Signed-off-by: Fabiano Rosas <[email protected]>

Yeah this looks better in general, feel free to take:

Reviewed-by: Peter Xu <[email protected]>

One thing to mention:

Strictly speaking, migration_tls_channel_connect() doesn't fall into the
"async op" category - it was invoked from migration core, so logically it
can still keep its errp, then the migration core should also be able to
process the error in migration_channel_connect().  It's not like the other
two "async ops" where migration context was lost.

IOW, I can kind of see why we used to pass an Error into the current
migration_channel_connect(), and it still makes some sense.  OTOH, it
doesn't really make sense to me to keep passing it to migration_connect()..

But since that's the only user of migration_tls_channel_connect(), I assume
it's not a huge deal, anyway.

> ---
>  migration/channel.c    | 46 +++++++++++++++++-------------------------
>  migration/channel.h    |  4 +---
>  migration/exec.c       |  2 +-
>  migration/fd.c         |  2 +-
>  migration/file.c       |  2 +-
>  migration/migration.c  | 11 ++--------
>  migration/migration.h  |  3 ++-
>  migration/rdma.c       |  2 +-
>  migration/socket.c     | 17 ++++++++--------
>  migration/tls.c        | 19 ++++++++---------
>  migration/tls.h        |  4 +---
>  migration/trace-events |  2 +-
>  12 files changed, 49 insertions(+), 65 deletions(-)
> 
> diff --git a/migration/channel.c b/migration/channel.c
> index ba14f66d85..7243b99108 100644
> --- a/migration/channel.c
> +++ b/migration/channel.c
> @@ -60,38 +60,30 @@ void migration_channel_process_incoming(QIOChannel *ioc)
>   *
>   * @s: Current migration state
>   * @ioc: Channel to which we are connecting
> - * @error: Error indicating failure to connect, free'd here
>   */
> -void migration_channel_connect(MigrationState *s,
> -                               QIOChannel *ioc,
> -                               Error *error)
> +void migration_channel_connect(MigrationState *s, QIOChannel *ioc)
>  {
> -    trace_migration_set_outgoing_channel(
> -        ioc, object_get_typename(OBJECT(ioc)), error);
> +    trace_migration_set_outgoing_channel(ioc, 
> object_get_typename(OBJECT(ioc)));
>  
> -    if (!error) {
> -        if (migrate_channel_requires_tls_upgrade(ioc)) {
> -            migration_tls_channel_connect(s, ioc, &error);
> +    if (migrate_channel_requires_tls_upgrade(ioc)) {
> +        migration_tls_channel_connect(s, ioc);
>  
> -            if (!error) {
> -                /* tls_channel_connect will call back to this
> -                 * function after the TLS handshake,
> -                 * so we mustn't call migration_connect until then
> -                 */
> -
> -                return;
> -            }
> -        } else {
> -            QEMUFile *f = qemu_file_new_output(ioc);
> -
> -            migration_ioc_register_yank(ioc);
> -
> -            qemu_mutex_lock(&s->qemu_file_lock);
> -            s->to_dst_file = f;
> -            qemu_mutex_unlock(&s->qemu_file_lock);
> -        }
> +        /*
> +         * async: the above will call back to this function after
> +         * the TLS handshake is successfully completed.
> +         */
> +        return;
>      }
> -    migration_connect(s, error);
> +
> +    QEMUFile *f = qemu_file_new_output(ioc);
> +
> +    migration_ioc_register_yank(ioc);
> +
> +    qemu_mutex_lock(&s->qemu_file_lock);
> +    s->to_dst_file = f;
> +    qemu_mutex_unlock(&s->qemu_file_lock);
> +
> +    migration_connect(s);
>  }
>  
>  
> diff --git a/migration/channel.h b/migration/channel.h
> index 2215091323..ccfeaaef18 100644
> --- a/migration/channel.h
> +++ b/migration/channel.h
> @@ -20,9 +20,7 @@
>  
>  void migration_channel_process_incoming(QIOChannel *ioc);
>  
> -void migration_channel_connect(MigrationState *s,
> -                               QIOChannel *ioc,
> -                               Error *error_in);
> +void migration_channel_connect(MigrationState *s, QIOChannel *ioc);
>  
>  int migration_channel_read_peek(QIOChannel *ioc,
>                                  const char *buf,
> diff --git a/migration/exec.c b/migration/exec.c
> index 78fe0fff13..d83a07435a 100644
> --- a/migration/exec.c
> +++ b/migration/exec.c
> @@ -55,7 +55,7 @@ void exec_start_outgoing_migration(MigrationState *s, 
> strList *command,
>      }
>  
>      qio_channel_set_name(ioc, "migration-exec-outgoing");
> -    migration_channel_connect(s, ioc, NULL);
> +    migration_channel_connect(s, ioc);
>      object_unref(OBJECT(ioc));
>  }
>  
> diff --git a/migration/fd.c b/migration/fd.c
> index c956b260a4..0144a70742 100644
> --- a/migration/fd.c
> +++ b/migration/fd.c
> @@ -70,7 +70,7 @@ void fd_start_outgoing_migration(MigrationState *s, const 
> char *fdname, Error **
>      }
>  
>      qio_channel_set_name(ioc, "migration-fd-outgoing");
> -    migration_channel_connect(s, ioc, NULL);
> +    migration_channel_connect(s, ioc);
>      object_unref(OBJECT(ioc));
>  }
>  
> diff --git a/migration/file.c b/migration/file.c
> index c490f2b219..7bb9c1c79f 100644
> --- a/migration/file.c
> +++ b/migration/file.c
> @@ -122,7 +122,7 @@ void file_start_outgoing_migration(MigrationState *s,
>          return;
>      }
>      qio_channel_set_name(ioc, "migration-file-outgoing");
> -    migration_channel_connect(s, ioc, NULL);
> +    migration_channel_connect(s, ioc);
>  }
>  
>  static gboolean file_accept_incoming_migration(QIOChannel *ioc,
> diff --git a/migration/migration.c b/migration/migration.c
> index a66b2d7aaf..5c6c76f110 100644
> --- a/migration/migration.c
> +++ b/migration/migration.c
> @@ -1572,7 +1572,7 @@ static void migrate_error_free(MigrationState *s)
>      }
>  }
>  
> -static void migration_connect_error_propagate(MigrationState *s, Error 
> *error)
> +void migration_connect_error_propagate(MigrationState *s, Error *error)
>  {
>      MigrationStatus current = s->state;
>      MigrationStatus next = MIGRATION_STATUS_NONE;
> @@ -4033,7 +4033,7 @@ fail_setup:
>      return NULL;
>  }
>  
> -void migration_connect(MigrationState *s, Error *error_in)
> +void migration_connect(MigrationState *s)
>  {
>      Error *local_err = NULL;
>      uint64_t rate_limit;
> @@ -4041,13 +4041,6 @@ void migration_connect(MigrationState *s, Error 
> *error_in)
>      int ret;
>  
>      s->expected_downtime = migrate_downtime_limit();
> -    if (error_in) {
> -        migration_connect_error_propagate(s, error_in);
> -        if (s->error) {
> -            error_report_err(error_copy(s->error));
> -        }
> -        return;
> -    }
>  
>      if (resume) {
>          /* This is a resumed migration */
> diff --git a/migration/migration.h b/migration/migration.h
> index 4d42e8f9a7..f340cd518d 100644
> --- a/migration/migration.h
> +++ b/migration/migration.h
> @@ -532,10 +532,11 @@ void migration_incoming_process(void);
>  
>  bool  migration_has_all_channels(void);
>  
> +void migration_connect_error_propagate(MigrationState *s, Error *error);
>  void migrate_error_propagate(MigrationState *s, Error *error);
>  bool migrate_has_error(MigrationState *s);
>  
> -void migration_connect(MigrationState *s, Error *error_in);
> +void migration_connect(MigrationState *s);
>  
>  int migration_call_notifiers(MigrationState *s, MigrationEventType type,
>                               Error **errp);
> diff --git a/migration/rdma.c b/migration/rdma.c
> index 337b415889..596a1aba0b 100644
> --- a/migration/rdma.c
> +++ b/migration/rdma.c
> @@ -3997,7 +3997,7 @@ void rdma_start_outgoing_migration(void *opaque,
>  
>      s->to_dst_file = rdma_new_output(rdma);
>      s->rdma_migration = true;
> -    migration_connect(s, NULL);
> +    migration_connect(s);
>      return;
>  return_path_err:
>      qemu_rdma_cleanup(rdma);
> diff --git a/migration/socket.c b/migration/socket.c
> index 426f363b99..298bac30cc 100644
> --- a/migration/socket.c
> +++ b/migration/socket.c
> @@ -59,24 +59,25 @@ static void socket_outgoing_migration(QIOTask *task,
>                                        gpointer opaque)
>  {
>      struct SocketConnectData *data = opaque;
> -    QIOChannel *sioc = QIO_CHANNEL(qio_task_get_source(task));
> +    g_autoptr(QIOChannel) sioc = QIO_CHANNEL(qio_task_get_source(task));
>      Error *err = NULL;
>  
>      if (qio_task_propagate_error(task, &err)) {
> -        trace_migration_socket_outgoing_error(error_get_pretty(err));
> -           goto out;
> +        goto err;
>      }
>  
> -    trace_migration_socket_outgoing_connected();
> -
>      if (migrate_zero_copy_send() &&
>          !qio_channel_has_feature(sioc, QIO_CHANNEL_FEATURE_WRITE_ZERO_COPY)) 
> {
>          error_setg(&err, "Zero copy send feature not detected in host 
> kernel");
> +        goto err;
>      }
>  
> -out:
> -    migration_channel_connect(data->s, sioc, err);
> -    object_unref(OBJECT(sioc));
> +    trace_migration_socket_outgoing_connected();
> +    migration_channel_connect(data->s, sioc);
> +    return;
> +err:
> +    trace_migration_socket_outgoing_error(error_get_pretty(err));
> +    migration_connect_error_propagate(data->s, err);
>  }
>  
>  void socket_start_outgoing_migration(MigrationState *s,
> diff --git a/migration/tls.c b/migration/tls.c
> index 82f58cbc78..a54e8e6e14 100644
> --- a/migration/tls.c
> +++ b/migration/tls.c
> @@ -104,16 +104,17 @@ static void migration_tls_outgoing_handshake(QIOTask 
> *task,
>                                               gpointer opaque)
>  {
>      MigrationState *s = opaque;
> -    QIOChannel *ioc = QIO_CHANNEL(qio_task_get_source(task));
> +    g_autoptr(QIOChannel) ioc = QIO_CHANNEL(qio_task_get_source(task));
>      Error *err = NULL;
>  
>      if (qio_task_propagate_error(task, &err)) {
>          trace_migration_tls_outgoing_handshake_error(error_get_pretty(err));
> -    } else {
> -        trace_migration_tls_outgoing_handshake_complete();
> +        migration_connect_error_propagate(s, err);
> +        return;
>      }
> -    migration_channel_connect(s, ioc, err);
> -    object_unref(OBJECT(ioc));
> +
> +    trace_migration_tls_outgoing_handshake_complete();
> +    migration_channel_connect(s, ioc);
>  }
>  
>  QIOChannelTLS *migration_tls_client_create(QIOChannel *ioc,
> @@ -129,14 +130,14 @@ QIOChannelTLS *migration_tls_client_create(QIOChannel 
> *ioc,
>      return qio_channel_tls_new_client(ioc, creds, migrate_tls_hostname(), 
> errp);
>  }
>  
> -void migration_tls_channel_connect(MigrationState *s,
> -                                   QIOChannel *ioc,
> -                                   Error **errp)
> +void migration_tls_channel_connect(MigrationState *s, QIOChannel *ioc)
>  {
>      QIOChannelTLS *tioc;
> +    Error *local_err = NULL;
>  
> -    tioc = migration_tls_client_create(ioc, errp);
> +    tioc = migration_tls_client_create(ioc, &local_err);
>      if (!tioc) {
> +        migration_connect_error_propagate(s, local_err);
>          return;
>      }
>  
> diff --git a/migration/tls.h b/migration/tls.h
> index 7cd9c76013..7399c42edf 100644
> --- a/migration/tls.h
> +++ b/migration/tls.h
> @@ -29,9 +29,7 @@ void migration_tls_channel_process_incoming(QIOChannel 
> *ioc, Error **errp);
>  QIOChannelTLS *migration_tls_client_create(QIOChannel *ioc,
>                                             Error **errp);
>  
> -void migration_tls_channel_connect(MigrationState *s,
> -                                   QIOChannel *ioc,
> -                                   Error **errp);
> +void migration_tls_channel_connect(MigrationState *s, QIOChannel *ioc);
>  void migration_tls_channel_end(QIOChannel *ioc, Error **errp);
>  /* Whether the QIO channel requires further TLS handshake? */
>  bool migrate_channel_requires_tls_upgrade(QIOChannel *ioc);
> diff --git a/migration/trace-events b/migration/trace-events
> index da8f909cac..cbf10d0b63 100644
> --- a/migration/trace-events
> +++ b/migration/trace-events
> @@ -204,7 +204,7 @@ migration_transferred_bytes(uint64_t qemu_file, uint64_t 
> multifd, uint64_t rdma)
>  
>  # channel.c
>  migration_set_incoming_channel(void *ioc, const char *ioctype) "ioc=%p 
> ioctype=%s"
> -migration_set_outgoing_channel(void *ioc, const char *ioctype, void *err)  
> "ioc=%p ioctype=%s err=%p"
> +migration_set_outgoing_channel(void *ioc, const char *ioctype) "ioc=%p 
> ioctype=%s"
>  
>  # global_state.c
>  migrate_state_too_big(void) ""
> -- 
> 2.51.0
> 

-- 
Peter Xu


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