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

[Lin Ma <lma@suse.com>]

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);
+        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);
+
+    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