Patchwork [v2] Add interface to traverse the qmp command list by QmpCommand

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Submitter Mark Wu
Date Oct. 8, 2013, 6:23 a.m.
Message ID <1381213389-11440-1-git-send-email-wudxw@linux.vnet.ibm.com>
Download mbox | patch
Permalink /patch/281331/
State New
Headers show

Comments

Mark Wu - Oct. 8, 2013, 6:23 a.m.
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>
---
Changes:
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 |  5 ++--
 qapi/qmp-registry.c         | 27 +++---------------
 qga/commands.c              | 38 ++++++++++---------------
 qga/main.c                  | 68 +++++++++++++++++----------------------------
 4 files changed, 48 insertions(+), 90 deletions(-)
Eric Blake - Oct. 8, 2013, 1:15 p.m.
On 10/08/2013 12:23 AM, 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>
> ---
> Changes:
> 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 |  5 ++--
>  qapi/qmp-registry.c         | 27 +++---------------
>  qga/commands.c              | 38 ++++++++++---------------
>  qga/main.c                  | 68 +++++++++++++++++----------------------------
>  4 files changed, 48 insertions(+), 90 deletions(-)

Reviewed-by: Eric Blake <eblake@redhat.com>

> +++ 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) {

This (and several other instances) accesses cmd->name directly where we
were formally using the string from the returned list.  Should these
spots be modified to go through an accessor method instead, similar to
qmp_command_is_enabled, so that QmpCommand can be treated as an opaque
type from this file?
Michael Roth - Oct. 8, 2013, 8:01 p.m.
Quoting Mark Wu (2013-10-08 01:23:09)
> 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>
> ---
> Changes:
> 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 |  5 ++--
>  qapi/qmp-registry.c         | 27 +++---------------
>  qga/commands.c              | 38 ++++++++++---------------
>  qga/main.c                  | 68 +++++++++++++++++----------------------------
>  4 files changed, 48 insertions(+), 90 deletions(-)
> 
> diff --git a/include/qapi/qmp/dispatch.h b/include/qapi/qmp/dispatch.h
> index 1ce11f5..b6eb49e 100644
> --- a/include/qapi/qmp/dispatch.h
> +++ b/include/qapi/qmp/dispatch.h
> @@ -47,9 +47,10 @@ 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);
>  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..3fcf10e 100644
> --- a/qapi/qmp-registry.c
> +++ b/qapi/qmp-registry.c
> @@ -66,35 +66,16 @@ 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 false;
> +    return cmd->enabled;
>  }
> 
> -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..ff2ee03 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 = opaque;
> +    if (g_list_find_custom(blacklist, cmd->name, ga_strcmp) == NULL &&
> +        !cmd->enabled) {

qmp_command_is_enabled(cmd)

I also agree with Eric's comments about using an accessor for cmd->name to
we can continue treating QmpCommand as an opaque.

Other than that, looks good.

Patch

diff --git a/include/qapi/qmp/dispatch.h b/include/qapi/qmp/dispatch.h
index 1ce11f5..b6eb49e 100644
--- a/include/qapi/qmp/dispatch.h
+++ b/include/qapi/qmp/dispatch.h
@@ -47,9 +47,10 @@  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);
 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..3fcf10e 100644
--- a/qapi/qmp-registry.c
+++ b/qapi/qmp-registry.c
@@ -66,35 +66,16 @@  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 false;
+    return cmd->enabled;
 }
 
-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..ff2ee03 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 = 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);