[PATCH] md: optimise reconstruction when re-adding a recently failed drive.

When an array is degraded, bit in the intent-bitmap are never cleared.  So if
a recently failed drive is re-added, we only need to reconstruct the block
that are still reflected in the bitmap.

This patch adds support for this re-adding.

Signed-off-by: Neil Brown <neilb@cse.unsw.edu.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 4 insertions, 0 deletions

diff --git a/include/linux/raid/md_k.h b/include/linux/raid/md_k.h
index 16e94a9f0f8c..6cdcb4434c6c 100644
--- a/include/linux/raid/md_k.h
+++ b/include/linux/raid/md_k.h
@@ -183,6 +183,10 @@ struct mdk_rdev_s
 
         int desc_nr;                    /* descriptor index in the superblock */
         int raid_disk;                  /* role of device in array */
+        int saved_raid_disk;            /* role that device used to have in the
+                                         * array and could again if we did a partial
+                                         * resync from the bitmap
+                                         */
 
         atomic_t        nr_pending;     /* number of pending requests.
                                          * only maintained for arrays that