--- old/src/share/vm/gc_implementation/g1/g1CollectedHeap.cpp	2013-02-26 10:10:11.852712805 -0800
+++ new/src/share/vm/gc_implementation/g1/g1CollectedHeap.cpp	2013-02-26 10:10:11.638047496 -0800
@@ -1765,7 +1765,7 @@
     update_committed_space(old_end, new_end);
 
     FreeRegionList expansion_list("Local Expansion List");
-    MemRegion mr = _hrs.expand_by(old_end, new_end, &expansion_list);
+    MemRegion mr = _hrs.expand_to(new_end, &expansion_list);
     assert(mr.start() == old_end, "post-condition");
     // mr might be a smaller region than what was requested if
     // expand_by() was unable to allocate the HeapRegion instances
@@ -1820,7 +1820,9 @@
   aligned_shrink_bytes = align_size_down(aligned_shrink_bytes,
                                          HeapRegion::GrainBytes);
   uint num_regions_deleted = 0;
-  MemRegion mr = _hrs.shrink_by(aligned_shrink_bytes, &num_regions_deleted);
+  HeapWord* desired_new_end =
+        (HeapWord*) _g1_storage.high() - (aligned_shrink_bytes / HeapWordSize);
+  MemRegion mr = _hrs.shrink_to(desired_new_end, &num_regions_deleted);
   HeapWord* old_end = (HeapWord*) _g1_storage.high();
   assert(mr.end() == old_end, "post-condition");
 
@@ -2039,10 +2041,12 @@
                            g1_rs.size()/HeapWordSize);
 
   _g1_storage.initialize(g1_rs, 0);
-  _g1_committed = MemRegion((HeapWord*)_g1_storage.low(), (size_t) 0);
+  _g1_committed = MemRegion((HeapWord*) _g1_storage.low(), (size_t) 0);
   _hrs.initialize((HeapWord*) _g1_reserved.start(),
-                  (HeapWord*) _g1_reserved.end(),
-                  _expansion_regions);
+                  (HeapWord*) _g1_reserved.end());
+  assert(_hrs.max_length() == _expansion_regions,
+         err_msg("max length: %u expansion regions: %u",
+                 _hrs.max_length(), _expansion_regions));
 
   // 6843694 - ensure that the maximum region index can fit
   // in the remembered set structures.