[Qemu-devel] [PATCH v5 0/2] Add generic can_be_deleted to UserCreatableClass.

[Qemu-devel] [PATCH v5 0/2] Add generic can_be_deleted to UserCreatableClass.

[Lin Ma]

The patchset adds a generic can_be_deleted callback to UserCreatableClass.
It prevents removing a usercreatable object if the callback returns false.

Backends could implement the callback if it shoudn't be removed while it's
in use.

Thank Peter Crosthwaite, Paolo Bonzini, Andreas Färber and Igor Mammedov for
helping review.


ChangeLog:
V5:
Use specific caster instead of dynamic cast in user_creatable_can_be_deleted.

V4:
Add function user_creatable_can_be_deleted to wrapper can_be_deleted method.
Remove some unnecessary code.

V3:
Move the callback to the correct place: UserCreatableClass.
Move the backend callback implementation to hostmem.c.

V2:
Make it generic, add the can_be_deleted callback to TypeInfo and TypeImpl.
Implement the callback in hostmem-file.c and hostmem-ram.c.

V1:
Initial version, hard coded in object_del to prevent removing an in-use
host memory backend.


Lin Ma (2):
  qom: Add can_be_deleted callback to UserCreatableClass
  hostmem: Prevent removing an in-use memory backend

 backends/hostmem.c              | 14 ++++++++++++++
 include/qom/object_interfaces.h | 14 ++++++++++++++
 qmp.c                           |  5 +++++
 qom/object_interfaces.c         | 14 ++++++++++++++
 4 files changed, 47 insertions(+)

-- 
2.1.4

[Qemu-devel] [PATCH v5 1/2] qom: Add can_be_deleted callback to UserCreatableClass

[Lin Ma]

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         | 14 ++++++++++++++
 3 files changed, 33 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..48f54c9 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 use, can not be deleted", id);
+        return;
+    }
     object_unparent(obj);
 }
 
diff --git a/qom/object_interfaces.c b/qom/object_interfaces.c
index 6360818..608b436 100644
--- a/qom/object_interfaces.c
+++ b/qom/object_interfaces.c
@@ -18,6 +18,20 @@ void user_creatable_complete(Object *obj, Error **errp)
     }
 }
 
+bool user_creatable_can_be_deleted(Object *obj, Error **errp)
+{
+
+    UserCreatableClass *ucc;
+    UserCreatable *uc = USER_CREATABLE(obj);
+
+    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 = {
-- 
2.1.4

[Qemu-devel] [PATCH v5 2/2] hostmem: Prevent removing an in-use memory backend

[Lin Ma]

showing a memory device whose memdev is removed leads an assert:

(qemu) object_add memory-backend-ram,id=ram0,size=128M
(qemu) device_add pc-dimm,id=d0,memdev=ram0
(qemu) object_del ram0
(qemu) info memory-devices
**
ERROR:qom/object.c:1274:object_get_canonical_path_component:\
                            assertion failed: (obj->parent != NULL)
Aborted

The patch prevents removing an in-use mem backend and error out.

Signed-off-by: Lin Ma <lma@suse.com>
---
 backends/hostmem.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/backends/hostmem.c b/backends/hostmem.c
index 99e8f99..b7b6cf8 100644
--- a/backends/hostmem.c
+++ b/backends/hostmem.c
@@ -335,12 +335,26 @@ host_memory_backend_memory_complete(UserCreatable *uc, Error **errp)
     }
 }
 
+static bool
+host_memory_backend_can_be_deleted(UserCreatable *uc, Error **errp)
+{
+    MemoryRegion *mr;
+
+    mr = host_memory_backend_get_memory(MEMORY_BACKEND(uc), errp);
+    if (memory_region_is_mapped(mr)) {
+        return false;
+    } else {
+        return true;
+    }
+}
+
 static void
 host_memory_backend_class_init(ObjectClass *oc, void *data)
 {
     UserCreatableClass *ucc = USER_CREATABLE_CLASS(oc);
 
     ucc->complete = host_memory_backend_memory_complete;
+    ucc->can_be_deleted = host_memory_backend_can_be_deleted;
 }
 
 static const TypeInfo host_memory_backend_info = {
-- 
2.1.4

Re: [Qemu-devel] [PATCH v5 1/2] qom: Add can_be_deleted callback to UserCreatableClass

[Igor Mammedov]

On Sat, 28 Mar 2015 00:55:29 +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         | 14 ++++++++++++++
>  3 files changed, 33 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
s/obj/uc/
s/defined/implemented/

> + * @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.
drop ", otherwise the call does nothing"

> +bool user_creatable_can_be_deleted(Object *obj, Error **errp);
[...]
>  
> +bool user_creatable_can_be_deleted(Object *obj, Error **errp)
> +{
> +
> +    UserCreatableClass *ucc;
> +    UserCreatable *uc = USER_CREATABLE(obj);
Function description doesn't match what it does, I mean part
"otherwise the call does nothing."

How about changing prototype to:

bool user_creatable_can_be_deleted(UserCreatable *uc, Error **errp)

and calling it in qmp.c like:
  user_creatable_can_be_deleted(USER_CREATABLE(obj), errp);

Re: [Qemu-devel] [PATCH v5 1/2] qom: Add can_be_deleted callback to UserCreatableClass

[Lin Ma]

在 2015年03月28日 01:20, Igor Mammedov 写道:
> On Sat, 28 Mar 2015 00:55:29 +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         | 14 ++++++++++++++
>>   3 files changed, 33 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
> s/obj/uc/
> s/defined/implemented/
>
>> + * @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.
> drop ", otherwise the call does nothing"
>
>> +bool user_creatable_can_be_deleted(Object *obj, Error **errp);
> [...]
>>   
>> +bool user_creatable_can_be_deleted(Object *obj, Error **errp)
>> +{
>> +
>> +    UserCreatableClass *ucc;
>> +    UserCreatable *uc = USER_CREATABLE(obj);
> Function description doesn't match what it does, I mean part
> "otherwise the call does nothing."
>
> How about changing prototype to:
>
> bool user_creatable_can_be_deleted(UserCreatable *uc, Error **errp)
>
> and calling it in qmp.c like:
>    user_creatable_can_be_deleted(USER_CREATABLE(obj), errp);
That makes sense.

But If so, Does prototype of user_creatable_complete need to be changed 
as well by a new patch?

Re: [Qemu-devel] [PATCH v5 1/2] qom: Add can_be_deleted callback to UserCreatableClass

[Igor Mammedov]

On Sat, 28 Mar 2015 01:53:28 +0800
Lin Ma <lma@suse.com> wrote:

> 
> 在 2015年03月28日 01:20, Igor Mammedov 写道:
> > On Sat, 28 Mar 2015 00:55:29 +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         | 14 ++++++++++++++
> >>   3 files changed, 33 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
> > s/obj/uc/
> > s/defined/implemented/
> >
> >> + * @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.
> > drop ", otherwise the call does nothing"
> >
> >> +bool user_creatable_can_be_deleted(Object *obj, Error **errp);
> > [...]
> >>   
> >> +bool user_creatable_can_be_deleted(Object *obj, Error **errp)
> >> +{
> >> +
> >> +    UserCreatableClass *ucc;
> >> +    UserCreatable *uc = USER_CREATABLE(obj);
> > Function description doesn't match what it does, I mean part
> > "otherwise the call does nothing."
> >
> > How about changing prototype to:
> >
> > bool user_creatable_can_be_deleted(UserCreatable *uc, Error **errp)
> >
> > and calling it in qmp.c like:
> >    user_creatable_can_be_deleted(USER_CREATABLE(obj), errp);
> That makes sense.
> 
> But If so, Does prototype of user_creatable_complete need to be changed 
> as well by a new patch?
Yep, make it a separate patch though.