qom: optimize qdev_get_canonical_path using a parent link

The full tree search was a bit unreasonable.
Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>

hw/qdev.c

@@ -1229,6 +1229,8 @@ void qdev_property_add_child(DeviceState *dev, const char *name,
                       NULL, NULL, child, errp);
 
     qdev_ref(child);
+    g_assert(child->parent == NULL);
+    child->parent = dev;
 
     g_free(type);
 }
@@ -1307,48 +1309,38 @@ void qdev_property_add_link(DeviceState *dev, const char *name,
     g_free(full_type);
 }
 
-static gchar *qdev_get_path_in(DeviceState *parent, DeviceState *dev)
+gchar *qdev_get_canonical_path(DeviceState *dev)
 {
-    DeviceProperty *prop;
+    DeviceState *root = qdev_get_root();
+    char *newpath = NULL, *path = NULL;
 
-    if (parent == dev) {
-        return g_strdup("");
-    }
+    while (dev != root) {
+        DeviceProperty *prop = NULL;
 
-    QTAILQ_FOREACH(prop, &parent->properties, node) {
-        gchar *subpath;
+        g_assert(dev->parent != NULL);
 
-        if (!strstart(prop->type, "child<", NULL)) {
-            continue;
-        }
+        QTAILQ_FOREACH(prop, &dev->parent->properties, node) {
+            if (!strstart(prop->type, "child<", NULL)) {
+                continue;
+            }
 
-        /* Check to see if the device is one of parent's children */
-        if (prop->opaque == dev) {
-            return g_strdup(prop->name);
+            if (prop->opaque == dev) {
+                if (path) {
+                    newpath = g_strdup_printf("%s/%s", prop->name, path);
+                    g_free(path);
+                    path = newpath;
+                } else {
+                    path = g_strdup(prop->name);
+                }
+                break;
+            }
         }
 
-        /* Check to see if the device is a child of our child */
-        subpath = qdev_get_path_in(prop->opaque, dev);
-        if (subpath) {
-            gchar *path;
+        g_assert(prop != NULL);
 
-            path = g_strdup_printf("%s/%s", prop->name, subpath);
-            g_free(subpath);
-
-            return path;
-        }
+        dev = dev->parent;
     }
 
-    return NULL;
-}
-
-gchar *qdev_get_canonical_path(DeviceState *dev)
-{
-    gchar *path, *newpath;
-
-    path = qdev_get_path_in(qdev_get_root(), dev);
-    g_assert(path != NULL);
-
     newpath = g_strdup_printf("/%s", path);
     g_free(path);
 

hw/qdev.h

@@ -92,6 +92,10 @@ struct DeviceState {
     uint32_t ref;
 
     QTAILQ_HEAD(, DeviceProperty) properties;
+
+    /* Do not, under any circumstance, use this parent link below anywhere
+     * outside of qdev.c.  You have been warned. */
+    DeviceState *parent;
 };
 
 typedef void (*bus_dev_printfn)(Monitor *mon, DeviceState *dev, int indent);