[RFC PATCH v3 12/30] migration/multifd: Allow QIOTask error reporting without an object

[Fabiano Rosas]

The only way for the channel backend to report an error to the multifd
core during creation is by setting the QIOTask error. We must allow
the channel backend to set the error even if the QIOChannel has failed
to be created, which means the QIOTask source object would be NULL.

At multifd_new_send_channel_async() move the QOM casting of the
channel until after we have checked for the QIOTask error.

Signed-off-by: Fabiano Rosas <farosas@suse.de>
---
context: When doing multifd + file, it's possible that we fail to open
the file. I'll use the empty QIOTask to report the error back to
multifd.
---
 migration/multifd.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/migration/multifd.c b/migration/multifd.c
index 9625640d61..123ff0dec0 100644
--- a/migration/multifd.c
+++ b/migration/multifd.c
@@ -865,8 +865,7 @@ static bool multifd_channel_connect(MultiFDSendParams *p,
     return true;
 }
 
-static void multifd_new_send_channel_cleanup(MultiFDSendParams *p,
-                                             QIOChannel *ioc, Error *err)
+static void multifd_new_send_channel_cleanup(MultiFDSendParams *p, Error *err)
 {
      migrate_set_error(migrate_get_current(), err);
      /* Error happen, we need to tell who pay attention to me */
@@ -878,20 +877,20 @@ static void 
multifd_new_send_channel_cleanup(MultiFDSendParams *p,
       * its status.
       */
      p->quit = true;
-     object_unref(OBJECT(ioc));
      error_free(err);
 }
 
 static void multifd_new_send_channel_async(QIOTask *task, gpointer opaque)
 {
     MultiFDSendParams *p = opaque;
-    QIOChannel *ioc = QIO_CHANNEL(qio_task_get_source(task));
+    Object *obj = qio_task_get_source(task);
     Error *local_err = NULL;
 
     trace_multifd_new_send_channel_async(p->id);
     if (!qio_task_propagate_error(task, &local_err)) {
-        p->c = ioc;
-        qio_channel_set_delay(p->c, false);
+        QIOChannel *ioc = QIO_CHANNEL(obj);
+
+        qio_channel_set_delay(ioc, false);
         p->running = true;
         if (multifd_channel_connect(p, ioc, &local_err)) {
             return;
@@ -899,7 +898,8 @@ static void multifd_new_send_channel_async(QIOTask *task, 
gpointer opaque)
     }
 
     trace_multifd_new_send_channel_async_error(p->id, local_err);
-    multifd_new_send_channel_cleanup(p, ioc, local_err);
+    multifd_new_send_channel_cleanup(p, local_err);
+    object_unref(obj);
 }
 
 static void multifd_new_send_channel_create(gpointer opaque)
-- 
2.35.3