+ /*
+ * There are currently two references to the buffer - the active
+ * LRU reference and the buf log item. What we are about to do
+ * here - simulate a failed IO completion - requires 3
+ * references.
+ *
+ * The LRU reference is removed by the xfs_buf_stale() call. The
+ * buf item reference is removed by the xfs_buf_iodone()
+ * callback that is run by xfs_buf_do_callbacks() during ioend
+ * processing (via the bp->b_iodone callback), and then finally
+ * the ioend processing will drop the IO reference if the buffer
+ * is marked XBF_ASYNC.
+ *
+ * Hence we need to take an additional reference here so that IO
+ * completion processing doesn't free the buffer prematurely.
+ */