Re: [Qemu-devel] [PATCH v4 1/2] qom: Add can_be_deleted callback to UserCreatableClass

[Lin Ma <lma@suse.com>]

在 2015年03月27日 22:35, Igor Mammedov 写道:
> On Fri, 27 Mar 2015 13:36:11 +0800
> Lin Ma <lma@suse.com> wrote:
>
>> If backends implement the can_be_deleted and it returns false,
>> Then the qmp_object_del won't delete the given backends.
>>
>> Signed-off-by: Lin Ma <lma@suse.com>
>> ---
>>   include/qom/object_interfaces.h | 14 ++++++++++++++
>>   qmp.c                           |  5 +++++
>>   qom/object_interfaces.c         | 15 +++++++++++++++
>>   3 files changed, 34 insertions(+)
>>
>> diff --git a/include/qom/object_interfaces.h b/include/qom/object_interfaces.h
>> index b792283..012b653 100644
>> --- a/include/qom/object_interfaces.h
>> +++ b/include/qom/object_interfaces.h
>> @@ -25,6 +25,8 @@ typedef struct UserCreatable {
>>    * UserCreatableClass:
>>    * @parent_class: the base class
>>    * @complete: callback to be called after @obj's properties are set.
>> + * @can_be_deleted: callback to be called before an object is removed
>> + * to check if @obj can be removed safely.
>>    *
>>    * Interface is designed to work with -object/object-add/object_add
>>    * commands.
>> @@ -47,6 +49,7 @@ typedef struct UserCreatableClass {
>>   
>>       /* <public> */
>>       void (*complete)(UserCreatable *uc, Error **errp);
>> +    bool (*can_be_deleted)(UserCreatable *uc, Error **errp);
>>   } UserCreatableClass;
>>   
>>   /**
>> @@ -59,4 +62,15 @@ typedef struct UserCreatableClass {
>>    * nothing.
>>    */
>>   void user_creatable_complete(Object *obj, Error **errp);
>> +
>> +/**
>> + * user_creatable_can_be_deleted:
>> + * @obj: the object whose can_be_deleted() method is called if defined
>> + * @errp: if an error occurs, a pointer to an area to store the error
>> + *
>> + * Wrapper to call can_be_deleted() method if one of types it's inherited
>> + * from implements USER_CREATABLE interface, otherwise the call does
>> + * nothing.
>> + */
>> +bool user_creatable_can_be_deleted(Object *obj, Error **errp);
>>   #endif
>> diff --git a/qmp.c b/qmp.c
>> index c479e77..dc61da1 100644
>> --- a/qmp.c
>> +++ b/qmp.c
>> @@ -711,6 +711,11 @@ void qmp_object_del(const char *id, Error **errp)
>>           error_setg(errp, "object id not found");
>>           return;
>>       }
>> +
>> +    if (!user_creatable_can_be_deleted(obj, errp)) {
>> +        error_setg(errp, "%s is in used, can not be deleted", id);
>                                  ^^^ is in use || is used
                                                  Thanks for catching 
this. I'll modify it to 'in use'
>> +        return;
>> +    }
>>       object_unparent(obj);
>>   }
>>   
>> diff --git a/qom/object_interfaces.c b/qom/object_interfaces.c
>> index 6360818..25ae6ca 100644
>> --- a/qom/object_interfaces.c
>> +++ b/qom/object_interfaces.c
>> @@ -18,6 +18,21 @@ void user_creatable_complete(Object *obj, Error **errp)
>>       }
>>   }
>>   
>> +bool user_creatable_can_be_deleted(Object *obj, Error **errp)
>> +{
>> +
>> +    UserCreatableClass *ucc;
>> +    UserCreatable *uc =
>> +        (UserCreatable *)object_dynamic_cast(obj, TYPE_USER_CREATABLE);
> direc cast is wron, pls use type specific caster with QOM objects
> in this case you can even drop dynamic cast since /objects holds
> only TYPE_USER_CREATABLE objects and just do
>    UserCreatable *uc = USER_CREATABLE(obj)
will do.
> you don't check for null pointer anyway
May I have your suggestion about checking the null pointer? says:
if (!uc) {
     return false;  // is this make sense?
}
>
>> +
>> +    ucc = USER_CREATABLE_GET_CLASS(uc);
>> +    if (ucc->can_be_deleted) {
>> +        return ucc->can_be_deleted(uc, errp);
>> +    } else {
>> +        return true;
>> +    }
>> +}
>> +
>>   static void register_types(void)
>>   {
>>       static const TypeInfo uc_interface_info = {
>