[PATCH] md: teach raid5 the difference between 'check' and 'repair'.

With this, raid5 can be asked to check parity without repairing it.  It also
keeps a count of the number of incorrect parity blocks found (mismatches) and
reports them through sysfs.

Signed-off-by: Neil Brown <[email protected]>
Cc: Greg KH <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

include/linux/raid/md_k.h

@@ -175,6 +175,10 @@ struct mddev_s
 	sector_t			resync_mark_cnt;/* blocks written at resync_mark */
 
 	sector_t			resync_max_sectors; /* may be set by personality */
+
+	sector_t			resync_mismatches; /* count of sectors where
+							    * parity/replica mismatch found
+							    */
 	/* recovery/resync flags 
 	 * NEEDED:   we might need to start a resync/recover
 	 * RUNNING:  a thread is running, or about to be started