migration: small changes around rate-limiting

This patch extracts a few small changes from the next patch, which
are unrelated to adding generic rate-limiting functionality to
QEMUFile.  Make migration_set_rate_limit a simple accessor, and
use qemu_file_set_rate_limit consistently.  Also fix a typo where
INT_MAX should have been SIZE_MAX.

Reviewed-by: Orit Wasserman <owasserm@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>

migration.c

@@ -462,10 +462,15 @@ void qmp_migrate_set_speed(int64_t value, Error **errp)
     if (value < 0) {
         value = 0;
     }
+    if (value > SIZE_MAX) {
+        value = SIZE_MAX;
+    }
 
     s = migrate_get_current();
     s->bandwidth_limit = value;
-    qemu_file_set_rate_limit(s->file, s->bandwidth_limit);
+    if (s->file) {
+        qemu_file_set_rate_limit(s->file, s->bandwidth_limit / XFER_LIMIT_RATIO);
+    }
 }
 
 void qmp_migrate_set_downtime(double value, Error **errp)
@@ -567,11 +572,8 @@ static int64_t migration_set_rate_limit(void *opaque, int64_t new_rate)
     if (qemu_file_get_error(s->file)) {
         goto out;
     }
-    if (new_rate > SIZE_MAX) {
-        new_rate = SIZE_MAX;
-    }
 
-    s->xfer_limit = new_rate / XFER_LIMIT_RATIO;
+    s->xfer_limit = new_rate;
 
 out:
     return s->xfer_limit;
@@ -614,7 +616,7 @@ static void *migration_thread(void *opaque)
                 qemu_system_wakeup_request(QEMU_WAKEUP_REASON_OTHER);
                 old_vm_running = runstate_is_running();
                 vm_stop_force_state(RUN_STATE_FINISH_MIGRATE);
-                s->xfer_limit = INT_MAX;
+                qemu_file_set_rate_limit(s->file, INT_MAX);
                 qemu_savevm_state_complete(s->file);
                 qemu_mutex_unlock_iothread();
                 if (!qemu_file_get_error(s->file)) {
@@ -691,11 +693,12 @@ void migrate_fd_connect(MigrationState *s)
     /* This is a best 1st approximation. ns to ms */
     s->expected_downtime = max_downtime/1000000;
 
-    s->xfer_limit = s->bandwidth_limit / XFER_LIMIT_RATIO;
-
     s->cleanup_bh = qemu_bh_new(migrate_fd_cleanup, s);
     s->file = qemu_fopen_ops(s, &migration_file_ops);
 
+    qemu_file_set_rate_limit(s->file,
+                             s->bandwidth_limit / XFER_LIMIT_RATIO);
+
     qemu_thread_create(&s->thread, migration_thread, s,
                        QEMU_THREAD_JOINABLE);
     notifier_list_notify(&migration_state_notifiers, s);