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Re: [Qemu-devel] [PATCH] Add interface to traverse the qmp command list


From: Michael Roth
Subject: Re: [Qemu-devel] [PATCH] Add interface to traverse the qmp command list by QmpCommand
Date: Fri, 27 Sep 2013 11:16:06 -0500
User-agent: alot/0.3.4

Quoting Mark Wu (2013-09-25 20:56:39)
> 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) to O(n^2)
> 
> Signed-off-by: Mark Wu <address@hidden>

Thanks, the qmp_for_each_command stuff is a nice cleanup.

Looks good other than previous comments.

> ---
>  include/qapi/qmp/dispatch.h |  3 +-
>  qapi/qmp-registry.c         | 28 ++-----------------
>  qga/commands.c              | 39 ++++++++++----------------
>  qga/main.c                  | 68 
> +++++++++++++++++----------------------------
>  4 files changed, 45 insertions(+), 93 deletions(-)
> 
> diff --git a/include/qapi/qmp/dispatch.h b/include/qapi/qmp/dispatch.h
> index 1ce11f5..fb174f6 100644
> --- a/include/qapi/qmp/dispatch.h
> +++ b/include/qapi/qmp/dispatch.h
> @@ -48,8 +48,9 @@ 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);
>  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..844d597 100644
> --- a/qapi/qmp-registry.c
> +++ b/qapi/qmp-registry.c
> @@ -66,35 +66,11 @@ void qmp_enable_command(const char *name)
>      qmp_toggle_command(name, true);
>  }
> 
> -bool qmp_command_is_enabled(const char *name)
> +void qmp_for_each_command(qmp_cmd_callback_fn fn, void *opaque)
>  {
>      QmpCommand *cmd;
> 
>      QTAILQ_FOREACH(cmd, &qmp_commands, node) {
> -        if (strcmp(cmd->name, name) == 0) {
> -            return cmd->enabled;
> -        }
> +        fn(cmd, opaque);
>      }
> -
> -    return false;
> -}
> -
> -char **qmp_get_command_list(void)
> -{
> -    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++;
> -    }
> -
> -    return list_head;
>  }
> diff --git a/qga/commands.c b/qga/commands.c
> index 528b082..602cd47 100644
> --- a/qga/commands.c
> +++ b/qga/commands.c
> @@ -45,35 +45,26 @@ 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 = (GuestAgentInfo *)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_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 = g_malloc0(sizeof(GuestAgentCommandInfo));
> +    cmd_info->name = g_strdup(cmd->name);
> +    cmd_info->enabled = cmd->enabled;
> +    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..1741d3f 100644
> --- a/qga/main.c
> +++ b/qga/main.c
> @@ -347,48 +347,34 @@ 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);
> +    whitelisted = false;
> +    i = 0;
> +    while (ga_freeze_whitelist[i] != NULL) {
> +        if (strcmp(cmd->name, ga_freeze_whitelist[i]) == 0) {
> +            whitelisted = true;
>          }
> -        g_free(*list);
> -        list++;
> +        i++;
> +    }
> +    if (!whitelisted) {
> +        g_debug("disabling command: %s", cmd->name);
> +        qmp_disable_command(cmd->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 = (GList *)opaque;
> +    if (g_list_find_custom(blacklist, cmd->name, ga_strcmp) == NULL &&
> +        !cmd->enabled) {
> +        g_debug("enabling command: %s", cmd->name);
> +        qmp_enable_command(cmd->name);
>      }
> -    g_free(list_head);
>  }
> 
>  static bool ga_create_file(const char *path)
> @@ -424,7 +410,7 @@ 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 +446,7 @@ 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 +906,11 @@ int64_t ga_get_fd_handle(GAState *s, Error **errp)
>      return handle;
>  }
> 
> +static void ga_print_cmd(QmpCommand *cmd, void *opaque)
> +{
> +    printf("%s\n", cmd->name);
> +}
> +
>  int main(int argc, char **argv)
>  {
>      const char *sopt = "hVvdm:p:l:f:F::b:s:t:";
> @@ -996,15 +987,8 @@ 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 +1110,7 @@ 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);
> -- 
> 1.8.3.1



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