[Qemu-devel] [PATCH v3] Add interface to traverse the qmp command list by QmpCommand

[Qemu-devel] [PATCH v3] Add interface to traverse the qmp command list by QmpCommand

[Mark Wu]

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);
-- 
1.8.3.1

Re: [Qemu-devel] [PATCH v3] Add interface to traverse the qmp command list by QmpCommand

[Eric Blake]

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On 10/08/2013 08:39 PM, 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

As your two patches are related, I'd send them threaded under one cover
letter if you have to respin.  But maybe we don't need that...

> 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(-)
> 

> -struct GuestAgentInfo *qmp_guest_info(Error **err)
> +static void qmp_command_info(QmpCommand *cmd, void *opaque)
>  {

> -    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);

Oops, not using qmp_command_name().

Seems minor enough that if it is the only change after this much churn,
and the maintainer is willing to fix it on your behalf, I could live with:

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

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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Re: [Qemu-devel] [PATCH v3] Add interface to traverse the qmp command list by QmpCommand

[Mark Wu]

Thanks a lot for your all kind and helpful comments.  I would fix it by 
myself to save the time of maintainer :)
Then I have to beg your another review.    BTW,  I would like to ask if 
there's good tools or practice to perform
an incremental review in qemu patch works.

Thanks.
Mark.


On Wed 09 Oct 2013 10:58:04 AM CST, Eric Blake wrote:
> On 10/08/2013 08:39 PM, 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
>
> As your two patches are related, I'd send them threaded under one cover
> letter if you have to respin.  But maybe we don't need that...
>
>> 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(-)
>>
>
>> -struct GuestAgentInfo *qmp_guest_info(Error **err)
>> +static void qmp_command_info(QmpCommand *cmd, void *opaque)
>>   {
>
>> -    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);
>
> Oops, not using qmp_command_name().
>
> Seems minor enough that if it is the only change after this much churn,
> and the maintainer is willing to fix it on your behalf, I could live with:
>
> Reviewed-by: Eric Blake <eblake@redhat.com>
>