qemu-ga: Add interface to traverse the qmp command list by QmpCommand

In the original code, qmp_get_command_list is used to construct
a list of all commands' name. To get the information of all qga
commands, it traverses the name list and search the command info
with its name.  So it can cause O(n^2) in the number of commands.

This patch adds an interface to traverse the qmp command list by
QmpCommand to replace qmp_get_command_list. It can decrease the
complexity from O(n^2) to O(n).

Signed-off-by: Mark Wu <wudxw@linux.vnet.ibm.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
*fix up commit subject
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>

include/qapi/qmp/dispatch.h

@@ -47,9 +47,11 @@ QmpCommand *qmp_find_command(const char *name);
 QObject *qmp_dispatch(QObject *request);
 void qmp_disable_command(const char *name);
 void qmp_enable_command(const char *name);
-bool qmp_command_is_enabled(const char *name);
-char **qmp_get_command_list(void);
+bool qmp_command_is_enabled(const QmpCommand *cmd);
+const char *qmp_command_name(const QmpCommand *cmd);
 QObject *qmp_build_error_object(Error *errp);
+typedef void (*qmp_cmd_callback_fn)(QmpCommand *cmd, void *opaque);
+void qmp_for_each_command(qmp_cmd_callback_fn fn, void *opaque);
 
 #endif
 

qapi/qmp-registry.c

@@ -66,35 +66,21 @@ void qmp_enable_command(const char *name)
     qmp_toggle_command(name, true);
 }
 
-bool qmp_command_is_enabled(const char *name)
+bool qmp_command_is_enabled(const QmpCommand *cmd)
 {
-    QmpCommand *cmd;
-
-    QTAILQ_FOREACH(cmd, &qmp_commands, node) {
-        if (strcmp(cmd->name, name) == 0) {
-            return cmd->enabled;
-        }
-    }
+    return cmd->enabled;
+}
 
-    return false;
+const char *qmp_command_name(const QmpCommand *cmd)
+{
+    return cmd->name;
 }
 
-char **qmp_get_command_list(void)
+void qmp_for_each_command(qmp_cmd_callback_fn fn, void *opaque)
 {
     QmpCommand *cmd;
-    int count = 1;
-    char **list_head, **list;
-
-    QTAILQ_FOREACH(cmd, &qmp_commands, node) {
-        count++;
-    }
-
-    list_head = list = g_malloc0(count * sizeof(char *));
 
     QTAILQ_FOREACH(cmd, &qmp_commands, node) {
-        *list = g_strdup(cmd->name);
-        list++;
+        fn(cmd, opaque);
     }
-
-    return list_head;
 }

qga/commands.c

@@ -45,35 +45,27 @@ void qmp_guest_ping(Error **err)
     slog("guest-ping called");
 }
 
-struct GuestAgentInfo *qmp_guest_info(Error **err)
+static void qmp_command_info(QmpCommand *cmd, void *opaque)
 {
-    GuestAgentInfo *info = g_malloc0(sizeof(GuestAgentInfo));
+    GuestAgentInfo *info = opaque;
     GuestAgentCommandInfo *cmd_info;
     GuestAgentCommandInfoList *cmd_info_list;
-    char **cmd_list_head, **cmd_list;
-
-    info->version = g_strdup(QEMU_VERSION);
-
-    cmd_list_head = cmd_list = qmp_get_command_list();
-    if (*cmd_list_head == NULL) {
-        goto out;
-    }
 
-    while (*cmd_list) {
-        cmd_info = g_malloc0(sizeof(GuestAgentCommandInfo));
-        cmd_info->name = g_strdup(*cmd_list);
-        cmd_info->enabled = qmp_command_is_enabled(cmd_info->name);
+    cmd_info = g_malloc0(sizeof(GuestAgentCommandInfo));
+    cmd_info->name = g_strdup(qmp_command_name(cmd));
+    cmd_info->enabled = qmp_command_is_enabled(cmd);
 
-        cmd_info_list = g_malloc0(sizeof(GuestAgentCommandInfoList));
-        cmd_info_list->value = cmd_info;
-        cmd_info_list->next = info->supported_commands;
-        info->supported_commands = cmd_info_list;
+    cmd_info_list = g_malloc0(sizeof(GuestAgentCommandInfoList));
+    cmd_info_list->value = cmd_info;
+    cmd_info_list->next = info->supported_commands;
+    info->supported_commands = cmd_info_list;
+}
 
-        g_free(*cmd_list);
-        cmd_list++;
-    }
+struct GuestAgentInfo *qmp_guest_info(Error **err)
+{
+    GuestAgentInfo *info = g_malloc0(sizeof(GuestAgentInfo));
 
-out:
-    g_free(cmd_list_head);
+    info->version = g_strdup(QEMU_VERSION);
+    qmp_for_each_command(qmp_command_info, info);
     return info;
 }

qga/main.c

@@ -347,48 +347,35 @@ static gint ga_strcmp(gconstpointer str1, gconstpointer str2)
 }
 
 /* disable commands that aren't safe for fsfreeze */
-static void ga_disable_non_whitelisted(void)
+static void ga_disable_non_whitelisted(QmpCommand *cmd, void *opaque)
 {
-    char **list_head, **list;
-    bool whitelisted;
-    int i;
-
-    list_head = list = qmp_get_command_list();
-    while (*list != NULL) {
-        whitelisted = false;
-        i = 0;
-        while (ga_freeze_whitelist[i] != NULL) {
-            if (strcmp(*list, ga_freeze_whitelist[i]) == 0) {
-                whitelisted = true;
-            }
-            i++;
-        }
-        if (!whitelisted) {
-            g_debug("disabling command: %s", *list);
-            qmp_disable_command(*list);
+    bool whitelisted = false;
+    int i = 0;
+    const char *name = qmp_command_name(cmd);
+
+    while (ga_freeze_whitelist[i] != NULL) {
+        if (strcmp(name, ga_freeze_whitelist[i]) == 0) {
+            whitelisted = true;
         }
-        g_free(*list);
-        list++;
+        i++;
+    }
+    if (!whitelisted) {
+        g_debug("disabling command: %s", name);
+        qmp_disable_command(name);
     }
-    g_free(list_head);
 }
 
 /* [re-]enable all commands, except those explicitly blacklisted by user */
-static void ga_enable_non_blacklisted(GList *blacklist)
+static void ga_enable_non_blacklisted(QmpCommand *cmd, void *opaque)
 {
-    char **list_head, **list;
-
-    list_head = list = qmp_get_command_list();
-    while (*list != NULL) {
-        if (g_list_find_custom(blacklist, *list, ga_strcmp) == NULL &&
-            !qmp_command_is_enabled(*list)) {
-            g_debug("enabling command: %s", *list);
-            qmp_enable_command(*list);
-        }
-        g_free(*list);
-        list++;
+    GList *blacklist = opaque;
+    const char *name = qmp_command_name(cmd);
+
+    if (g_list_find_custom(blacklist, name, ga_strcmp) == NULL &&
+        !qmp_command_is_enabled(cmd)) {
+        g_debug("enabling command: %s", name);
+        qmp_enable_command(name);
     }
-    g_free(list_head);
 }
 
 static bool ga_create_file(const char *path)
@@ -424,7 +411,7 @@ void ga_set_frozen(GAState *s)
         return;
     }
     /* disable all non-whitelisted (for frozen state) commands */
-    ga_disable_non_whitelisted();
+    qmp_for_each_command(ga_disable_non_whitelisted, NULL);
     g_warning("disabling logging due to filesystem freeze");
     ga_disable_logging(s);
     s->frozen = true;
@@ -460,7 +447,7 @@ void ga_unset_frozen(GAState *s)
     }
 
     /* enable all disabled, non-blacklisted commands */
-    ga_enable_non_blacklisted(s->blacklist);
+    qmp_for_each_command(ga_enable_non_blacklisted, s->blacklist);
     s->frozen = false;
     if (!ga_delete_file(s->state_filepath_isfrozen)) {
         g_warning("unable to delete %s, fsfreeze may not function properly",
@@ -920,6 +907,11 @@ int64_t ga_get_fd_handle(GAState *s, Error **errp)
     return handle;
 }
 
+static void ga_print_cmd(QmpCommand *cmd, void *opaque)
+{
+    printf("%s\n", qmp_command_name(cmd));
+}
+
 int main(int argc, char **argv)
 {
     const char *sopt = "hVvdm:p:l:f:F::b:s:t:";
@@ -996,15 +988,8 @@ int main(int argc, char **argv)
             daemonize = 1;
             break;
         case 'b': {
-            char **list_head, **list;
             if (is_help_option(optarg)) {
-                list_head = list = qmp_get_command_list();
-                while (*list != NULL) {
-                    printf("%s\n", *list);
-                    g_free(*list);
-                    list++;
-                }
-                g_free(list_head);
+                qmp_for_each_command(ga_print_cmd, NULL);
                 return 0;
             }
             for (j = 0, i = 0, len = strlen(optarg); i < len; i++) {
@@ -1126,7 +1111,7 @@ int main(int argc, char **argv)
             s->deferred_options.log_filepath = log_filepath;
         }
         ga_disable_logging(s);
-        ga_disable_non_whitelisted();
+        qmp_for_each_command(ga_disable_non_whitelisted, NULL);
     } else {
         if (daemonize) {
             become_daemon(pid_filepath);