[PATCH] qga: return a more explicit error on why a command is disabled

[PATCH] qga: return a more explicit error on why a command is disabled

[marcandre.lureau]

From: Marc-André Lureau <marcandre.lureau@redhat.com>

qmp_disable_command() now takes an optional error string to return a
more explicit error message.

Fixes:
https://bugzilla.redhat.com/show_bug.cgi?id=1928806

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
---
 include/qapi/qmp/dispatch.h | 3 ++-
 qapi/qmp-dispatch.c         | 2 +-
 qapi/qmp-registry.c         | 9 +++++----
 qga/main.c                  | 4 ++--
 4 files changed, 10 insertions(+), 8 deletions(-)

diff --git a/include/qapi/qmp/dispatch.h b/include/qapi/qmp/dispatch.h
index 1486cac3ef..d50420cdd8 100644
--- a/include/qapi/qmp/dispatch.h
+++ b/include/qapi/qmp/dispatch.h
@@ -36,6 +36,7 @@ typedef struct QmpCommand
     QmpCommandOptions options;
     QTAILQ_ENTRY(QmpCommand) node;
     bool enabled;
+    const char *err_msg;
 } QmpCommand;
 
 typedef QTAILQ_HEAD(QmpCommandList, QmpCommand) QmpCommandList;
@@ -44,7 +45,7 @@ void qmp_register_command(QmpCommandList *cmds, const char *name,
                           QmpCommandFunc *fn, QmpCommandOptions options);
 const QmpCommand *qmp_find_command(const QmpCommandList *cmds,
                                    const char *name);
-void qmp_disable_command(QmpCommandList *cmds, const char *name);
+void qmp_disable_command(QmpCommandList *cmds, const char *name, const char *err_msg);
 void qmp_enable_command(QmpCommandList *cmds, const char *name);
 
 bool qmp_command_is_enabled(const QmpCommand *cmd);
diff --git a/qapi/qmp-dispatch.c b/qapi/qmp-dispatch.c
index 0a2b20a4e4..ce4bf56b2c 100644
--- a/qapi/qmp-dispatch.c
+++ b/qapi/qmp-dispatch.c
@@ -157,7 +157,7 @@ QDict *qmp_dispatch(const QmpCommandList *cmds, QObject *request,
     }
     if (!cmd->enabled) {
         error_set(&err, ERROR_CLASS_COMMAND_NOT_FOUND,
-                  "The command %s has been disabled for this instance",
+                  cmd->err_msg ?: "The command %s has been disabled for this instance",
                   command);
         goto out;
     }
diff --git a/qapi/qmp-registry.c b/qapi/qmp-registry.c
index 58c65b5052..ddc49b8f2d 100644
--- a/qapi/qmp-registry.c
+++ b/qapi/qmp-registry.c
@@ -43,26 +43,27 @@ const QmpCommand *qmp_find_command(const QmpCommandList *cmds, const char *name)
 }
 
 static void qmp_toggle_command(QmpCommandList *cmds, const char *name,
-                               bool enabled)
+                               bool enabled, const char *err_msg)
 {
     QmpCommand *cmd;
 
     QTAILQ_FOREACH(cmd, cmds, node) {
         if (strcmp(cmd->name, name) == 0) {
             cmd->enabled = enabled;
+            cmd->err_msg = err_msg;
             return;
         }
     }
 }
 
-void qmp_disable_command(QmpCommandList *cmds, const char *name)
+void qmp_disable_command(QmpCommandList *cmds, const char *name, const char *err_msg)
 {
-    qmp_toggle_command(cmds, name, false);
+    qmp_toggle_command(cmds, name, false, err_msg);
 }
 
 void qmp_enable_command(QmpCommandList *cmds, const char *name)
 {
-    qmp_toggle_command(cmds, name, true);
+    qmp_toggle_command(cmds, name, true, NULL);
 }
 
 bool qmp_command_is_enabled(const QmpCommand *cmd)
diff --git a/qga/main.c b/qga/main.c
index e7f8f3b161..c59b610691 100644
--- a/qga/main.c
+++ b/qga/main.c
@@ -375,7 +375,7 @@ static void ga_disable_non_whitelisted(const QmpCommand *cmd, void *opaque)
     }
     if (!whitelisted) {
         g_debug("disabling command: %s", name);
-        qmp_disable_command(&ga_commands, name);
+        qmp_disable_command(&ga_commands, name, "The command was disabled after fsfreeze.");
     }
 }
 
@@ -1329,7 +1329,7 @@ static GAState *initialize_agent(GAConfig *config, int socket_activation)
         s->blacklist = config->blacklist;
         do {
             g_debug("disabling command: %s", (char *)l->data);
-            qmp_disable_command(&ga_commands, l->data);
+            qmp_disable_command(&ga_commands, l->data, NULL);
             l = g_list_next(l);
         } while (l);
     }
-- 
2.29.0

Re: [PATCH] qga: return a more explicit error on why a command is disabled

[no-reply]

Patchew URL: https://patchew.org/QEMU/20210216133837.2347190-1-marcandre.lureau@redhat.com/



Hi,

This series seems to have some coding style problems. See output below for
more information:

Type: series
Message-id: 20210216133837.2347190-1-marcandre.lureau@redhat.com
Subject: [PATCH] qga: return a more explicit error on why a command is disabled

=== TEST SCRIPT BEGIN ===
#!/bin/bash
git rev-parse base > /dev/null || exit 0
git config --local diff.renamelimit 0
git config --local diff.renames True
git config --local diff.algorithm histogram
./scripts/checkpatch.pl --mailback base..
=== TEST SCRIPT END ===

Updating 3c8cf5a9c21ff8782164d1def7f44bd888713384
Switched to a new branch 'test'
a762179 qga: return a more explicit error on why a command is disabled

=== OUTPUT BEGIN ===
WARNING: line over 80 characters
#39: FILE: include/qapi/qmp/dispatch.h:48:
+void qmp_disable_command(QmpCommandList *cmds, const char *name, const char *err_msg);

WARNING: line over 80 characters
#52: FILE: qapi/qmp-dispatch.c:160:
+                  cmd->err_msg ?: "The command %s has been disabled for this instance",

WARNING: line over 80 characters
#79: FILE: qapi/qmp-registry.c:59:
+void qmp_disable_command(QmpCommandList *cmds, const char *name, const char *err_msg)

ERROR: line over 90 characters
#101: FILE: qga/main.c:378:
+        qmp_disable_command(&ga_commands, name, "The command was disabled after fsfreeze.");

total: 1 errors, 3 warnings, 70 lines checked

Commit a7621793c6d6 (qga: return a more explicit error on why a command is disabled) has style problems, please review.  If any of these errors
are false positives report them to the maintainer, see
CHECKPATCH in MAINTAINERS.
=== OUTPUT END ===

Test command exited with code: 1


The full log is available at
http://patchew.org/logs/20210216133837.2347190-1-marcandre.lureau@redhat.com/testing.checkpatch/?type=message.
---
Email generated automatically by Patchew [https://patchew.org/].
Please send your feedback to patchew-devel@redhat.com

Re: [PATCH] qga: return a more explicit error on why a command is disabled

[Peter Krempa]

On Tue, Feb 16, 2021 at 17:38:37 +0400, marcandre.lureau@redhat.com wrote:
> From: Marc-André Lureau <marcandre.lureau@redhat.com>
> 
> qmp_disable_command() now takes an optional error string to return a
> more explicit error message.
> 
> Fixes:
> https://bugzilla.redhat.com/show_bug.cgi?id=1928806
> 
> Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
> ---
>  include/qapi/qmp/dispatch.h | 3 ++-
>  qapi/qmp-dispatch.c         | 2 +-
>  qapi/qmp-registry.c         | 9 +++++----
>  qga/main.c                  | 4 ++--
>  4 files changed, 10 insertions(+), 8 deletions(-)

[...]

> diff --git a/qapi/qmp-dispatch.c b/qapi/qmp-dispatch.c
> index 0a2b20a4e4..ce4bf56b2c 100644
> --- a/qapi/qmp-dispatch.c
> +++ b/qapi/qmp-dispatch.c
> @@ -157,7 +157,7 @@ QDict *qmp_dispatch(const QmpCommandList *cmds, QObject *request,
>      }
>      if (!cmd->enabled) {
>          error_set(&err, ERROR_CLASS_COMMAND_NOT_FOUND,
> -                  "The command %s has been disabled for this instance",
> +                  cmd->err_msg ?: "The command %s has been disabled for this instance",

Passing in the formatting string from a variable looks shady and it's
hard to ensure that callers pass in the appropriate format modifier ...

>                    command);
>          goto out;
>      }

[...]

> diff --git a/qga/main.c b/qga/main.c
> index e7f8f3b161..c59b610691 100644
> --- a/qga/main.c
> +++ b/qga/main.c
> @@ -375,7 +375,7 @@ static void ga_disable_non_whitelisted(const QmpCommand *cmd, void *opaque)
>      }
>      if (!whitelisted) {
>          g_debug("disabling command: %s", name);
> -        qmp_disable_command(&ga_commands, name);
> +        qmp_disable_command(&ga_commands, name, "The command was disabled after fsfreeze.");

... such as here where '%s' is missing. Luckily that is not a problem
compared to when there would be more than one format modifier.

But the error message looks definitely better.

>      }
>  }

My suggestion would be to store a boolean flag that the command was
disabled due to an ongoing fsfreeze and then choose the appropriate
error message directly at the point where it's reported.

Re: [PATCH] qga: return a more explicit error on why a command is disabled

[Marc-André Lureau]

[-- Attachment #1: Type: text/plain, Size: 2561 bytes --]

On Tue, Feb 16, 2021 at 6:33 PM Peter Krempa <pkrempa@redhat.com> wrote:

> On Tue, Feb 16, 2021 at 17:38:37 +0400, marcandre.lureau@redhat.com wrote:
> > From: Marc-André Lureau <marcandre.lureau@redhat.com>
> >
> > qmp_disable_command() now takes an optional error string to return a
> > more explicit error message.
> >
> > Fixes:
> > https://bugzilla.redhat.com/show_bug.cgi?id=1928806
> >
> > Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
> > ---
> >  include/qapi/qmp/dispatch.h | 3 ++-
> >  qapi/qmp-dispatch.c         | 2 +-
> >  qapi/qmp-registry.c         | 9 +++++----
> >  qga/main.c                  | 4 ++--
> >  4 files changed, 10 insertions(+), 8 deletions(-)
>
> [...]
>
> > diff --git a/qapi/qmp-dispatch.c b/qapi/qmp-dispatch.c
> > index 0a2b20a4e4..ce4bf56b2c 100644
> > --- a/qapi/qmp-dispatch.c
> > +++ b/qapi/qmp-dispatch.c
> > @@ -157,7 +157,7 @@ QDict *qmp_dispatch(const QmpCommandList *cmds,
> QObject *request,
> >      }
> >      if (!cmd->enabled) {
> >          error_set(&err, ERROR_CLASS_COMMAND_NOT_FOUND,
> > -                  "The command %s has been disabled for this instance",
> > +                  cmd->err_msg ?: "The command %s has been disabled for
> this instance",
>
> Passing in the formatting string from a variable looks shady and it's
> hard to ensure that callers pass in the appropriate format modifier ...
>
> >                    command);
> >          goto out;
> >      }
>
> [...]
>
> > diff --git a/qga/main.c b/qga/main.c
> > index e7f8f3b161..c59b610691 100644
> > --- a/qga/main.c
> > +++ b/qga/main.c
> > @@ -375,7 +375,7 @@ static void ga_disable_non_whitelisted(const
> QmpCommand *cmd, void *opaque)
> >      }
> >      if (!whitelisted) {
> >          g_debug("disabling command: %s", name);
> > -        qmp_disable_command(&ga_commands, name);
> > +        qmp_disable_command(&ga_commands, name, "The command was
> disabled after fsfreeze.");
>
> ... such as here where '%s' is missing. Luckily that is not a problem
> compared to when there would be more than one format modifier.
>
>
Sure, although it's an internal API, I agree it's error prone.

But the error message looks definitely better.
>

> >      }
> >  }
>
> My suggestion would be to store a boolean flag that the command was
> disabled due to an ongoing fsfreeze and then choose the appropriate
> error message directly at the point where it's reported.
>

Let's make it an enum for the reason.
thanks


-- 
Marc-André Lureau

[-- Attachment #2: Type: text/html, Size: 3989 bytes --]

Re: [PATCH] qga: return a more explicit error on why a command is disabled

[Eric Blake]

On 2/16/21 7:38 AM, marcandre.lureau@redhat.com wrote:
> From: Marc-André Lureau <marcandre.lureau@redhat.com>
> 
> qmp_disable_command() now takes an optional error string to return a
> more explicit error message.
> 
> Fixes:
> https://bugzilla.redhat.com/show_bug.cgi?id=1928806
> 
> Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
> ---

> +++ b/qapi/qmp-dispatch.c
> @@ -157,7 +157,7 @@ QDict *qmp_dispatch(const QmpCommandList *cmds, QObject *request,
>      }
>      if (!cmd->enabled) {
>          error_set(&err, ERROR_CLASS_COMMAND_NOT_FOUND,
> -                  "The command %s has been disabled for this instance",
> +                  cmd->err_msg ?: "The command %s has been disabled for this instance",

No trailing dot (good),...

> +++ b/qga/main.c
> @@ -375,7 +375,7 @@ static void ga_disable_non_whitelisted(const QmpCommand *cmd, void *opaque)
>      }
>      if (!whitelisted) {
>          g_debug("disabling command: %s", name);
> -        qmp_disable_command(&ga_commands, name);
> +        qmp_disable_command(&ga_commands, name, "The command was disabled after fsfreeze.");

...while this introduces one (not good).

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org