- /* Allow some slack between valud of curr_events and last_events,
- * as there are some uninteresting races.
+ /* The difference between curr_events and last_events
+ * will be affected by any new non-sync IO (making
+ * curr_events bigger) and any difference in the amount of
+ * in-flight syncio (making current_events bigger or smaller)
+ * The amount in-flight is currently limited to
+ * 32*64K in raid1/10 and 256*PAGE_SIZE in raid5/6
+ * which is at most 4096 sectors.
+ * These numbers are fairly fragile and should be made
+ * more robust, probably by enforcing the
+ * 'window size' that md_do_sync sort-of uses.
+ *