--- a/hotspot/src/share/vm/memory/metaspace.cpp	Mon Nov 28 14:57:12 2016 +0100
+++ b/hotspot/src/share/vm/memory/metaspace.cpp	Wed Nov 23 14:36:32 2016 +0100
@@ -153,7 +153,7 @@
 
   // Map a size to a list index assuming that there are lists
   // for special, small, medium, and humongous chunks.
-  static ChunkIndex list_index(size_t size);
+  ChunkIndex list_index(size_t size);
 
   // Remove the chunk from its freelist.  It is
   // expected to be on one of the _free_chunks[] lists.
@@ -1794,7 +1794,11 @@
   st->print_cr("Sum free chunk total " SIZE_FORMAT "  count " SIZE_FORMAT,
                 sum_free_chunks(), sum_free_chunks_count());
 }
+
 ChunkList* ChunkManager::free_chunks(ChunkIndex index) {
+  assert(index == SpecializedIndex || index == SmallIndex || index == MediumIndex,
+         "Bad index: %d", (int)index);
+
   return &_free_chunks[index];
 }
 
@@ -1898,7 +1902,7 @@
   }
 
   assert((word_size <= chunk->word_size()) ||
-         list_index(chunk->word_size() == HumongousIndex),
+         (list_index(chunk->word_size()) == HumongousIndex),
          "Non-humongous variable sized chunk");
   Log(gc, metaspace, freelist) log;
   if (log.is_debug()) {
@@ -2371,22 +2375,18 @@
 }
 
 ChunkIndex ChunkManager::list_index(size_t size) {
-  switch (size) {
-    case SpecializedChunk:
-      assert(SpecializedChunk == ClassSpecializedChunk,
-             "Need branch for ClassSpecializedChunk");
-      return SpecializedIndex;
-    case SmallChunk:
-    case ClassSmallChunk:
-      return SmallIndex;
-    case MediumChunk:
-    case ClassMediumChunk:
-      return MediumIndex;
-    default:
-      assert(size > MediumChunk || size > ClassMediumChunk,
-             "Not a humongous chunk");
-      return HumongousIndex;
+  if (free_chunks(SpecializedIndex)->size() == size) {
+    return SpecializedIndex;
+  }
+  if (free_chunks(SmallIndex)->size() == size) {
+    return SmallIndex;
   }
+  if (free_chunks(MediumIndex)->size() == size) {
+    return MediumIndex;
+  }
+
+  assert(size > free_chunks(MediumIndex)->size(), "Not a humongous chunk");
+  return HumongousIndex;
 }
 
 void SpaceManager::deallocate(MetaWord* p, size_t word_size) {
@@ -2410,7 +2410,7 @@
 
   // Find the correct list and and set the current
   // chunk for that list.
-  ChunkIndex index = ChunkManager::list_index(new_chunk->word_size());
+  ChunkIndex index = chunk_manager()->list_index(new_chunk->word_size());
 
   if (index != HumongousIndex) {
     retire_current_chunk();
@@ -4034,6 +4034,43 @@
 
 // The following test is placed here instead of a gtest / unittest file
 // because the ChunkManager class is only available in this file.
+void ChunkManager_test_list_index() {
+  ChunkManager manager(ClassSpecializedChunk, ClassSmallChunk, ClassMediumChunk);
+
+  // Test previous bug where a query for a humongous class metachunk,
+  // incorrectly matched the non-class medium metachunk size.
+  {
+    assert(MediumChunk > ClassMediumChunk, "Precondition for test");
+
+    ChunkIndex index = manager.list_index(MediumChunk);
+
+    assert(index == HumongousIndex,
+           "Requested size is larger than ClassMediumChunk,"
+           " so should return HumongousIndex. Got index: %d", (int)index);
+  }
+
+  // Check the specified sizes as well.
+  {
+    ChunkIndex index = manager.list_index(ClassSpecializedChunk);
+    assert(index == SpecializedIndex, "Wrong index returned. Got index: %d", (int)index);
+  }
+  {
+    ChunkIndex index = manager.list_index(ClassSmallChunk);
+    assert(index == SmallIndex, "Wrong index returned. Got index: %d", (int)index);
+  }
+  {
+    ChunkIndex index = manager.list_index(ClassMediumChunk);
+    assert(index == MediumIndex, "Wrong index returned. Got index: %d", (int)index);
+  }
+  {
+    ChunkIndex index = manager.list_index(ClassMediumChunk + 1);
+    assert(index == HumongousIndex, "Wrong index returned. Got index: %d", (int)index);
+  }
+}
+
+
+// The following test is placed here instead of a gtest / unittest file
+// because the ChunkManager class is only available in this file.
 class SpaceManagerTest : AllStatic {
   friend void SpaceManager_test_adjust_initial_chunk_size();
 

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/hotspot/test/native/memory/test_chunkManager.cpp	Wed Nov 23 14:36:32 2016 +0100
@@ -0,0 +1,39 @@
+/*
+ * Copyright (c) 2016, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+#include "precompiled.hpp"
+
+// The test function is only available in debug builds
+#ifdef ASSERT
+
+#include "unittest.hpp"
+
+void ChunkManager_test_list_index();
+
+TEST(ChunkManager, list_index) {
+  // The ChunkManager is only available in metaspace.cpp,
+  // so the test code is located in that file.
+  ChunkManager_test_list_index();
+}
+
+#endif // ASSERT