diff -r 2294594fbe6c Modules/posixmodule.c
--- a/Modules/posixmodule.c	Mon Aug 12 13:29:11 2013 -0400
+++ b/Modules/posixmodule.c	Mon Aug 12 14:23:31 2013 -0400
@@ -10252,6 +10252,17 @@
             goto exit;
         }
 
+        /*
+         * On Linux using ZFS (native), if attr is >128 bytes,
+         * and we ask for 128 bytes, we successfully get 128 bytes
+         * and no error is indicated.  So we always retry if we
+         * got exactly what we asked for.
+         */
+        if (result == buffer_size && buffer_size != XATTR_SIZE_MAX) {
+            Py_DECREF(buffer);
+            continue;
+        }
+
         if (result != buffer_size) {
             /* Can only shrink. */
             _PyBytes_Resize(&buffer, result);