qemu: Report better error message when renaming to existing domain name

Signed-off-by: NMartin Kletzander <mkletzan@redhat.com>

src/qemu/qemu_driver.c

@@ -19907,6 +19907,7 @@ static int qemuDomainRename(virDomainPtr dom,
     virQEMUDriverPtr driver = dom->conn->privateData;
     virQEMUDriverConfigPtr cfg = NULL;
     virDomainObjPtr vm = NULL;
+    virDomainObjPtr tmp_dom = NULL;
     virObjectEventPtr event_new = NULL;
     virObjectEventPtr event_old = NULL;
     int ret = -1;
@@ -19961,6 +19962,21 @@ static int qemuDomainRename(virDomainPtr dom,
         goto endjob;
     }
 
+    /*
+     * This is a rather racy check, but still better than reporting
+     * internal error.  And since new_name != name here, there's no
+     * deadlock imminent.
+     */
+    tmp_dom = virDomainObjListFindByName(driver->domains, new_name);
+    if (tmp_dom) {
+        virObjectUnlock(tmp_dom);
+        virObjectUnref(tmp_dom);
+        virReportError(VIR_ERR_OPERATION_INVALID,
+                       _("domain with name '%s' already exists"),
+                       new_name);
+        goto endjob;
+    }
+
     if (VIR_STRDUP(new_dom_name, new_name) < 0)
         goto endjob;