Prior to this update, COPYing an object onto itself (e.g., to change its metadata) reliably produces a truncated object, if the source object was originally created with rgw older than RHCS 1.2 using a non-multi-part upload. If the object was originally created via a multi-part upload, or was created with a newer rgw, such as RHCS 1.2, the problem does not occur.
The truncated object has correct metadata, including the original size, but the underlying RADOS object is smaller. When a client attempts to fetch the object, it receives less data than indicated by the Content-Length, blocks for more, and eventually times out.
RGW has been updated to handle old manifests properly, and COPYing old objects in the above scenario works as expected.