Added TODO comment about a possible deadlock Marcus just found :-)

git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@23450 a95241bf-73f2-0310-859d-f6bbb57e9c96

src/system/kernel/vm/vm_page.cpp

@@ -1016,6 +1016,9 @@ page_writer(void* /*unused*/)
 			busyConditions[i].Unpublish();
 
 			mutex_unlock(&cache->lock);
+			// TODO: we need to release the cache references after all
+			// pages are made unbusy again - otherwise releasing a vnode
+			// could deadlock.
 			if (cache->store->ops->release_ref != NULL)
 				cache->store->ops->release_ref(cache->store);
 			vm_cache_release_ref(cache);