Add API for issuing 'balloon' monitor command

* src/qemu/qemu_monitor.c, src/qemu/qemu_monitor.h: Add new
  qemuMonitorSetBalloon() based on existing code in
  qemudDomainSetMemoryBalloon
* src/qemu/qemu_driver.c: Remove use of qemudDomainSetMemoryBalloon()
  in favour of qemuMonitorSetBalloon(). Fix error code when balloon
  is not supported

src/qemu/qemu_driver.c

@@ -107,9 +107,6 @@ static void qemudShutdownVMDaemon(virConnectPtr conn,
 
 static int qemudDomainGetMaxVcpus(virDomainPtr dom);
 
-static int qemudDomainSetMemoryBalloon(virConnectPtr conn,
-                                       virDomainObjPtr vm,
-                                       unsigned long newmem);
 static int qemuDetectVcpuPIDs(virConnectPtr conn,
                               virDomainObjPtr vm);
 
@@ -2137,7 +2134,7 @@ static int qemudStartVMDaemon(virConnectPtr conn,
         (qemuDetectVcpuPIDs(conn, vm) < 0) ||
         (qemudInitCpus(conn, vm, migrateFrom) < 0) ||
         (qemuInitPasswords(driver, vm) < 0) ||
-        (qemudDomainSetMemoryBalloon(conn, vm, vm->def->memory) < 0) ||
+        (qemuMonitorSetBalloon(vm, vm->def->memory) < 0) ||
         (virDomainSaveStatus(conn, driver->stateDir, vm) < 0)) {
         qemudShutdownVMDaemon(conn, driver, vm);
         ret = -1;
@@ -2999,50 +2996,6 @@ cleanup:
 }
 
 
-/*
- * Returns: 0 if balloon not supported, +1 if balloon query worked
- * or -1 on failure
- */
-static int qemudDomainSetMemoryBalloon(virConnectPtr conn,
-                                       virDomainObjPtr vm,
-                                       unsigned long newmem) {
-    char *cmd;
-    char *reply = NULL;
-    int ret = -1;
-
-    /*
-     * 'newmem' is in KB, QEMU monitor works in MB, and we all wish
-     * we just worked in bytes with unsigned long long everywhere.
-     */
-    if (virAsprintf(&cmd, "balloon %lu", (newmem / 1024)) < 0) {
-        virReportOOMError(conn);
-        goto cleanup;
-    }
-
-    if (qemudMonitorCommand(vm, cmd, &reply) < 0) {
-        qemudReportError(conn, dom, NULL, VIR_ERR_OPERATION_FAILED,
-                         "%s", _("could not balloon memory allocation"));
-        VIR_FREE(cmd);
-        goto cleanup;
-    }
-    VIR_FREE(cmd);
-
-    /* If the command failed qemu prints: 'unknown command'
-     * No message is printed on success it seems */
-    DEBUG ("%s: balloon reply: %s",vm->def->name,  reply);
-    if (strstr(reply, "\nunknown command:")) {
-        /* Don't set error - it is expected memory balloon fails on many qemu */
-        ret = 0;
-    } else {
-        ret = 1;
-    }
-
-cleanup:
-    VIR_FREE(reply);
-    return ret;
-}
-
-
 static int qemudDomainSetMemory(virDomainPtr dom, unsigned long newmem) {
     struct qemud_driver *driver = dom->conn->privateData;
     virDomainObjPtr vm;
@@ -3066,10 +3019,13 @@ static int qemudDomainSetMemory(virDomainPtr dom, unsigned long newmem) {
     }
 
     if (virDomainIsActive(vm)) {
-        ret = qemudDomainSetMemoryBalloon(dom->conn, vm, newmem);
-        if (ret == 0)
+        ret = qemuMonitorSetBalloon(vm, newmem);
+        /* Turn lack of balloon support into a fatal error */
+        if (ret == 0) {
             qemudReportError(dom->conn, dom, NULL, VIR_ERR_NO_SUPPORT,
                              "%s", _("cannot set memory of an active domain"));
+            ret = -1;
+        }
     } else {
         vm->def->memory = newmem;
         ret = 0;

src/qemu/qemu_monitor_text.c

@@ -551,6 +551,10 @@ error:
 /* The reply from QEMU contains 'ballon: actual=421' where value is in MB */
 #define BALLOON_PREFIX "balloon: actual="
 
+/*
+ * Returns: 0 if balloon not supported, +1 if balloon query worked
+ * or -1 on failure
+ */
 int qemuMonitorGetBalloonInfo(const virDomainObjPtr vm,
                               unsigned long *currmem)
 {
@@ -604,3 +608,46 @@ int qemuMonitorSetVNCPassword(const virDomainObjPtr vm,
     VIR_FREE(info);
     return 0;
 }
+
+/*
+ * Returns: 0 if balloon not supported, +1 if balloon adjust worked
+ * or -1 on failure
+ */
+int qemuMonitorSetBalloon(const virDomainObjPtr vm,
+                          unsigned long newmem)
+{
+    char *cmd;
+    char *reply = NULL;
+    int ret = -1;
+
+    /*
+     * 'newmem' is in KB, QEMU monitor works in MB, and we all wish
+     * we just worked in bytes with unsigned long long everywhere.
+     */
+    if (virAsprintf(&cmd, "balloon %lu", (newmem / 1024)) < 0) {
+        virReportOOMError(NULL);
+        return -1;
+    }
+
+    if (qemudMonitorCommand(vm, cmd, &reply) < 0) {
+        qemudReportError(NULL, NULL, NULL, VIR_ERR_OPERATION_FAILED,
+                         "%s", _("could not balloon memory allocation"));
+        VIR_FREE(cmd);
+        return -1;
+    }
+    VIR_FREE(cmd);
+
+    /* If the command failed qemu prints: 'unknown command'
+     * No message is printed on success it seems */
+    DEBUG ("%s: balloon reply: %s", vm->def->name,  reply);
+    if (strstr(reply, "\nunknown command:")) {
+        /* Don't set error - it is expected memory balloon fails on many qemu */
+        ret = 0;
+    } else {
+        ret = 1;
+    }
+
+    VIR_FREE(reply);
+    return ret;
+}
+

src/qemu/qemu_monitor_text.h

@@ -78,5 +78,7 @@ int qemuMonitorGetBalloonInfo(const virDomainObjPtr vm,
 
 int qemuMonitorSetVNCPassword(const virDomainObjPtr vm,
                               const char *password);
+int qemuMonitorSetBalloon(const virDomainObjPtr vm,
+                          unsigned long newmem);
 
 #endif /* QEMU_MONITOR_TEXT_H */