migration: simplify blockers

Modify migrate_add_blocker and migrate_del_blocker to take an Error **
reason.  This allows migration to own the Error object, so that if
an error occurs in migrate_add_blocker, migration code can free the Error
and clear the client handle, simplifying client code.  It also simplifies
the migrate_del_blocker call site.

In addition, this is a pre-requisite for a proposed future patch that would
add a mode argument to migration requests to support live update, and
maintain a list of blockers for each mode.  A blocker may apply to a single
mode or to multiple modes, and passing Error** will allow one Error object
to be registered for multiple modes.

No functional change.

Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
Tested-by: Michael Galaxy <mgalaxy@akamai.com>
Reviewed-by: Michael Galaxy <mgalaxy@akamai.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
Message-ID: <1697634216-84215-1-git-send-email-steven.sistare@oracle.com>

1 files changed, 2 insertions, 3 deletions

diff --git a/ui/vdagent.c b/ui/vdagent.c
index 00d36a8677..d8f2f95432 100644
--- a/ui/vdagent.c
+++ b/ui/vdagent.c
@@ -671,7 +671,7 @@ static void vdagent_chr_open(Chardev *chr,
     return;
 #endif
 
-    if (migrate_add_blocker(vd->migration_blocker, errp) != 0) {
+    if (migrate_add_blocker(&vd->migration_blocker, errp) != 0) {
         return;
     }
 
@@ -924,13 +924,12 @@ static void vdagent_chr_fini(Object *obj)
 {
     VDAgentChardev *vd = QEMU_VDAGENT_CHARDEV(obj);
 
-    migrate_del_blocker(vd->migration_blocker);
+    migrate_del_blocker(&vd->migration_blocker);
     vdagent_disconnect(vd);
     if (vd->mouse_hs) {
         qemu_input_handler_unregister(vd->mouse_hs);
     }
     buffer_free(&vd->outbuf);
-    error_free(vd->migration_blocker);
 }
 
 static const TypeInfo vdagent_chr_type_info = {