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

[Lin Ma]

在 2015年03月27日 22:35, Igor Mammedov 写道:
> On Fri, 27 Mar 2015 13:36:11 +0800
> Lin Ma <address@hidden> 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 <address@hidden>
> > ---
> >   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 = {