Return the async task tag for exec typed incoming migration in
exec_start_incoming_migration().

Signed-off-by: Peter Xu <peterx@redhat.com>
---
 migration/exec.c | 18 +++++++++++-------
 migration/exec.h |  2 +-
 2 files changed, 12 insertions(+), 8 deletions(-)

diff --git a/migration/exec.c b/migration/exec.c
index 08b599e..ef1fb4c 100644
--- a/migration/exec.c
+++ b/migration/exec.c
@@ -52,7 +52,11 @@ static gboolean exec_accept_incoming_migration(QIOChannel *ioc,
     return FALSE; /* unregister */
 }
 
-void exec_start_incoming_migration(const char *command, Error **errp)
+/*
+ * Returns the tag ID of the watch that is attached to global main
+ * loop (>0), or zero if failure detected.
+ */
+guint exec_start_incoming_migration(const char *command, Error **errp)
 {
     QIOChannel *ioc;
     const char *argv[] = { "/bin/sh", "-c", command, NULL };
@@ -62,13 +66,13 @@ void exec_start_incoming_migration(const char *command, Error **errp)
                                                     O_RDWR,
                                                     errp));
     if (!ioc) {
-        return;
+        return 0;
     }
 
     qio_channel_set_name(ioc, "migration-exec-incoming");
-    qio_channel_add_watch(ioc,
-                          G_IO_IN,
-                          exec_accept_incoming_migration,
-                          NULL,
-                          NULL);
+    return qio_channel_add_watch(ioc,
+                                 G_IO_IN,
+                                 exec_accept_incoming_migration,
+                                 NULL,
+                                 NULL);
 }
diff --git a/migration/exec.h b/migration/exec.h
index b210ffd..0a7aada 100644
--- a/migration/exec.h
+++ b/migration/exec.h
@@ -19,7 +19,7 @@
 
 #ifndef QEMU_MIGRATION_EXEC_H
 #define QEMU_MIGRATION_EXEC_H
-void exec_start_incoming_migration(const char *host_port, Error **errp);
+guint exec_start_incoming_migration(const char *host_port, Error **errp);
 
 void exec_start_outgoing_migration(MigrationState *s, const char *host_port,
                                    Error **errp);
-- 
2.7.4