[PATCH] md: fix raid6 resync check/repair code

raid6 currently does not check the P/Q syndromes when doing a resync, it just
calculates the correct value and writes it.  Doing the check can reduce writes
(often to 0) for a resync, and it is needed to properly implement the

  echo check > sync_action

operation.

This patch implements the appropriate checks and tidies up some related code.

It also allows raid6 user-requested resync to bypass the intent bitmap.

Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 2 insertions, 0 deletions

diff --git a/include/linux/raid/raid5.h b/include/linux/raid/raid5.h
index f025ba6fb14c..e9c1c0d4f90b 100644
--- a/include/linux/raid/raid5.h
+++ b/include/linux/raid/raid5.h
@@ -228,6 +228,8 @@ struct raid5_private_data {
                                             * Cleared when a sync completes.
                                             */
 
+        struct page             *spare_page; /* Used when checking P/Q in raid6 */
+
         /*
          * Free stripes pool
          */