Re: [Qemu-devel] [PATCH 1/2] Add interface to traverse the qmp command list by QmpCommand

[Mark Wu <wudxw@linux.vnet.ibm.com>]

On Wed 09 Oct 2013 10:36:21 AM CST, Mark Wu wrote:
> 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>
> ---
> v3:
>      Add an accessor for cmd->name to avoid exposing internals of QmpCommand
> v2:
> 	1. Keep the signature of qmp_command_is_enabled (per Eric and Michael)
>      2. Remove the unnecessary pointer castings (per Eric)
>
>   include/qapi/qmp/dispatch.h |  6 ++--
>   qapi/qmp-registry.c         | 30 +++++-------------
>   qga/commands.c              | 38 +++++++++--------------
>   qga/main.c                  | 75 ++++++++++++++++++---------------------------
>   4 files changed, 57 insertions(+), 92 deletions(-)
>
> diff --git a/include/qapi/qmp/dispatch.h b/include/qapi/qmp/dispatch.h
> index 1ce11f5..7d759ef 100644
> --- a/include/qapi/qmp/dispatch.h
> +++ b/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
>
> diff --git a/qapi/qmp-registry.c b/qapi/qmp-registry.c
> index 28bbbe8..5e26710 100644
> --- a/qapi/qmp-registry.c
> +++ b/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;
>   }
> diff --git a/qga/commands.c b/qga/commands.c
> index 528b082..063b22b 100644
> --- a/qga/commands.c
> +++ b/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(cmd->name);
> +    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;
>   }
> diff --git a/qga/main.c b/qga/main.c
> index 6c746c8..c58b26a 100644
> --- a/qga/main.c
> +++ b/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);

Please ignore this mail because of the wrong patch revision number.  
Sorry for that.