md/raid5: clearly differentiate 'before' and 'after' stripes during reshape.

During a raid5 reshape, we have some stripes in the cache that are
'before' the reshape (and are still to be processed) and some that are
'after'.  They are currently differentiated by having different
->disks values as the only reshape current supported involves changing
the number of disks.

However we will soon support reshapes that do not change the number
of disks (chunk parity or chunk size).  So make the difference more
explicit with a 'generation' number.

Signed-off-by: NeilBrown <neilb@suse.de>

1 files changed, 3 insertions, 0 deletions

diff --git a/drivers/md/raid5.h b/drivers/md/raid5.h
index b2edcc434e41..a081fb40a5a2 100644
--- a/drivers/md/raid5.h
+++ b/drivers/md/raid5.h
@@ -198,6 +198,8 @@ struct stripe_head {
         struct hlist_node       hash;
         struct list_head        lru;          /* inactive_list or handle_list */
         struct raid5_private_data *raid_conf;
+        short                   generation;     /* increments with every
+                                                 * reshape */
         sector_t                sector;         /* sector of this row */
         short                   pd_idx;         /* parity disk index */
         short                   qd_idx;         /* 'Q' disk index for raid6 */
@@ -348,6 +350,7 @@ struct raid5_private_data {
          */
         sector_t                reshape_safe;
         int                     previous_raid_disks;
+        short                   generation; /* increments with every reshape */
 
         struct list_head        handle_list; /* stripes needing handling */
         struct list_head        hold_list; /* preread ready stripes */