Add a 'nop' lock driver implementation.

To allow hypervisor drivers to assume that a lock driver impl
will be guaranteed to exist, provide a 'nop' impl that is
compiled into the library

* src/Makefile.am: Add nop driver
* src/locking/lock_driver_nop.c, src/locking/lock_driver_nop.h:
  Nop lock driver implementation
* src/locking/lock_manager.c: Enable direct access of 'nop'
  driver, instead of dlopen()ing it.

src/Makefile.am

@@ -94,7 +94,9 @@ DRIVER_SOURCES =						\
 		fdstream.c fdstream.h                 \
 		$(NODE_INFO_SOURCES)				\
 		libvirt.c libvirt_internal.h			\
-		locking/lock_manager.c locking/lock_manager.h
+		locking/lock_manager.c locking/lock_manager.h   \
+		locking/lock_driver.h 				\
+		locking/lock_driver_nop.h locking/lock_driver_nop.c
 
 
 # XML configuration format handling sources

src/locking/lock_driver_nop.c

+/*
+ * lock_driver_nop.c: A lock driver which locks nothing
+ *
+ * Copyright (C) 2010-2011 Red Hat, Inc.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307  USA
+ *
+ */
+
+#include <config.h>
+
+#include "lock_driver_nop.h"
+#include "memory.h"
+#include "logging.h"
+#include "uuid.h"
+
+
+static int virLockManagerNopInit(unsigned int version,
+                                 unsigned int flags)
+{
+    VIR_DEBUG("version=%u flags=%u", version, flags);
+
+    return 0;
+}
+
+static int virLockManagerNopDeinit(void)
+{
+    VIR_DEBUG(" ");
+
+    return 0;
+}
+
+
+static int virLockManagerNopNew(virLockManagerPtr lock ATTRIBUTE_UNUSED,
+                                unsigned int type ATTRIBUTE_UNUSED,
+                                size_t nparams ATTRIBUTE_UNUSED,
+                                virLockManagerParamPtr params ATTRIBUTE_UNUSED,
+                                unsigned int flags ATTRIBUTE_UNUSED)
+{
+    return 0;
+}
+
+static int virLockManagerNopAddResource(virLockManagerPtr lock ATTRIBUTE_UNUSED,
+                                        unsigned int type ATTRIBUTE_UNUSED,
+                                        const char *name ATTRIBUTE_UNUSED,
+                                        size_t nparams ATTRIBUTE_UNUSED,
+                                        virLockManagerParamPtr params ATTRIBUTE_UNUSED,
+                                        unsigned int flags ATTRIBUTE_UNUSED)
+{
+
+    return 0;
+}
+
+
+static int virLockManagerNopAcquire(virLockManagerPtr lock ATTRIBUTE_UNUSED,
+                                    const char *state ATTRIBUTE_UNUSED,
+                                    unsigned int flags ATTRIBUTE_UNUSED)
+{
+
+    return 0;
+}
+
+static int virLockManagerNopRelease(virLockManagerPtr lock ATTRIBUTE_UNUSED,
+                                    char **state,
+                                    unsigned int flags ATTRIBUTE_UNUSED)
+{
+    *state = NULL;
+
+    return 0;
+}
+
+static int virLockManagerNopInquire(virLockManagerPtr lock ATTRIBUTE_UNUSED,
+                                    char **state,
+                                    unsigned int flags ATTRIBUTE_UNUSED)
+{
+
+    *state = NULL;
+
+    return 0;
+}
+
+static void virLockManagerNopFree(virLockManagerPtr lock ATTRIBUTE_UNUSED)
+{
+}
+
+virLockDriver virLockDriverNop =
+{
+    .version = VIR_LOCK_MANAGER_VERSION,
+    .flags = 0,
+
+    .drvInit = virLockManagerNopInit,
+    .drvDeinit = virLockManagerNopDeinit,
+
+    .drvNew = virLockManagerNopNew,
+    .drvFree = virLockManagerNopFree,
+
+    .drvAddResource = virLockManagerNopAddResource,
+
+    .drvAcquire = virLockManagerNopAcquire,
+    .drvRelease = virLockManagerNopRelease,
+
+    .drvInquire = virLockManagerNopInquire,
+};

src/locking/lock_driver_nop.h

+/*
+ * lock_driver_nop.h: A lock driver which locks nothing
+ *
+ * Copyright (C) 2010-2011 Red Hat, Inc.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307  USA
+ *
+ */
+
+#ifndef __VIR_LOCK_DRIVER_NOP_H__
+# define __VIR_LOCK_DRIVER_NOP_H__
+
+# include "lock_driver.h"
+
+extern virLockDriver virLockDriverNop;
+
+
+#endif /* __VIR_LOCK_DRIVER_NOP_H__ */

src/locking/lock_manager.c

@@ -22,6 +22,7 @@
 #include <config.h>
 
 #include "lock_manager.h"
+#include "lock_driver_nop.h"
 #include "virterror_internal.h"
 #include "logging.h"
 #include "util.h"
@@ -123,35 +124,39 @@ virLockManagerPluginPtr virLockManagerPluginNew(const char *name,
     const char *moddir = getenv("LIBVIRT_LOCK_MANAGER_PLUGIN_DIR");
     char *modfile = NULL;
 
-    if (moddir == NULL)
-        moddir = DEFAULT_LOCK_MANAGER_PLUGIN_DIR;
+    if (STREQ(name, "nop")) {
+        driver = &virLockDriverNop;
+    } else {
+        if (moddir == NULL)
+            moddir = DEFAULT_LOCK_MANAGER_PLUGIN_DIR;
 
-    VIR_DEBUG("Module load %s from %s", name, moddir);
+        VIR_DEBUG("Module load %s from %s", name, moddir);
 
-    if (virAsprintf(&modfile, "%s/%s.so", moddir, name) < 0) {
-        virReportOOMError();
-        return NULL;
-    }
+        if (virAsprintf(&modfile, "%s/%s.so", moddir, name) < 0) {
+            virReportOOMError();
+            return NULL;
+        }
 
-    if (access(modfile, R_OK) < 0) {
-        virReportSystemError(errno,
-                             _("Plugin %s not accessible"),
-                             modfile);
-        goto cleanup;
-    }
+        if (access(modfile, R_OK) < 0) {
+            virReportSystemError(errno,
+                                 _("Plugin %s not accessible"),
+                                 modfile);
+            goto cleanup;
+        }
 
-    handle = dlopen(modfile, RTLD_NOW | RTLD_LOCAL);
-    if (!handle) {
-        virLockError(VIR_ERR_SYSTEM_ERROR,
-                     _("Failed to load plugin %s: %s"),
-                     modfile, dlerror());
-        goto cleanup;
-    }
+        handle = dlopen(modfile, RTLD_NOW | RTLD_LOCAL);
+        if (!handle) {
+            virLockError(VIR_ERR_SYSTEM_ERROR,
+                         _("Failed to load plugin %s: %s"),
+                         modfile, dlerror());
+            goto cleanup;
+        }
 
-    if (!(driver = dlsym(handle, "virLockDriverImpl"))) {
-        virLockError(VIR_ERR_INTERNAL_ERROR, "%s",
-                     _("Missing plugin initialization symbol 'virLockDriverImpl'"));
-        goto cleanup;
+        if (!(driver = dlsym(handle, "virLockDriverImpl"))) {
+            virLockError(VIR_ERR_INTERNAL_ERROR, "%s",
+                         _("Missing plugin initialization symbol 'virLockDriverImpl'"));
+            goto cleanup;
+        }
     }
 
     if (driver->drvInit(VIR_LOCK_MANAGER_VERSION, flags) < 0) {