md/raid6: remove expectation that Q device is immediately after P device.

Code currently assumes that the devices in a raid6 stripe are
  0 1 ... N-1 P Q
in some rotated order.  We will shortly add new layouts in which
this strict pattern is broken.
So remove this expectation.  We still assume that the data disks
are roughly in-order.  However P and Q can be inserted anywhere within
that order.

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

1 files changed, 8 insertions, 7 deletions

diff --git a/drivers/md/raid5.h b/drivers/md/raid5.h
index 0ed22dff56e0..0c7375ad12bd 100644
--- a/drivers/md/raid5.h
+++ b/drivers/md/raid5.h
@@ -196,15 +196,16 @@ enum reconstruct_states {
 
 struct stripe_head {
         struct hlist_node       hash;
-        struct list_head        lru;                    /* inactive_list or handle_list */
-        struct raid5_private_data       *raid_conf;
-        sector_t                sector;                 /* sector of this row */
-        int                     pd_idx;                 /* parity disk index */
-        unsigned long           state;                  /* state flags */
-        atomic_t                count;                  /* nr of active thread/requests */
+        struct list_head        lru;          /* inactive_list or handle_list */
+        struct raid5_private_data *raid_conf;
+        sector_t                sector;         /* sector of this row */
+        short                   pd_idx;         /* parity disk index */
+        short                   qd_idx;         /* 'Q' disk index for raid6 */
+        unsigned long           state;          /* state flags */
+        atomic_t                count;        /* nr of active thread/requests */
         spinlock_t              lock;
         int                     bm_seq; /* sequence number for bitmap flushes */
-        int                     disks;                  /* disks in stripe */
+        int                     disks;          /* disks in stripe */
         enum check_states       check_state;
         enum reconstruct_states reconstruct_state;
         /* stripe_operations