[PATCH v3 8/9] memory: Do not create circular reference with subregion

[Akihiko Odaki]

memory_region_update_container_subregions() calls memory_region_ref()
on behalf of the owner of the container. memory_region_ref() must not
be called if the owner of the container also owns the subregion.

Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
---
 system/memory.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/system/memory.c b/system/memory.c
index 2d6952136066..09c98042e443 100644
--- a/system/memory.c
+++ b/system/memory.c
@@ -2625,7 +2625,10 @@ static void 
memory_region_update_container_subregions(MemoryRegion *subregion)
 
     memory_region_transaction_begin();
 
-    memory_region_ref(subregion);
+    if (mr->owner != subregion->owner) {
+        memory_region_ref(subregion);
+    }
+
     QTAILQ_FOREACH(other, &mr->subregions, subregions_link) {
         if (subregion->priority >= other->priority) {
             QTAILQ_INSERT_BEFORE(other, subregion, subregions_link);
@@ -2683,7 +2686,11 @@ void memory_region_del_subregion(MemoryRegion *mr,
         assert(alias->mapped_via_alias >= 0);
     }
     QTAILQ_REMOVE(&mr->subregions, subregion, subregions_link);
-    memory_region_unref(subregion);
+
+    if (mr->owner != subregion->owner) {
+        memory_region_unref(subregion);
+    }
+
     memory_region_update_pending |= mr->enabled && subregion->enabled;
     memory_region_transaction_commit();
 }

-- 
2.45.2