[PATCH] md: Only checkpoint expansion progress occasionally

Instead of checkpointing at each stripe, only checkpoint when a new write
would overwrite uncheckpointed data.  Block any write to the uncheckpointed
area.  Arbitrarily checkpoint at least every 3Meg.

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, 3 insertions, 0 deletions

diff --git a/include/linux/raid/raid5.h b/include/linux/raid/raid5.h
index abcdf0d0658a..914af667044f 100644
--- a/include/linux/raid/raid5.h
+++ b/include/linux/raid/raid5.h
@@ -217,6 +217,9 @@ struct raid5_private_data {
 
         /* used during an expand */
         sector_t                expand_progress;        /* MaxSector when no expand happening */
+        sector_t                expand_lo; /* from here up to expand_progress it out-of-bounds
+                                            * as we haven't flushed the metadata yet
+                                            */
         int                     previous_raid_disks;
 
         struct list_head        handle_list; /* stripes needing handling */