md/raid6: asynchronous raid6 operations

[ Based on an original patch by Yuri Tikhonov ]

The raid_run_ops routine uses the asynchronous offload api and
the stripe_operations member of a stripe_head to carry out xor+pq+copy
operations asynchronously, outside the lock.

The operations performed by RAID-6 are the same as in the RAID-5 case
except for no support of STRIPE_OP_PREXOR operations. All the others
are supported:
STRIPE_OP_BIOFILL
 - copy data into request buffers to satisfy a read request
STRIPE_OP_COMPUTE_BLK
 - generate missing blocks (1 or 2) in the cache from the other blocks
STRIPE_OP_BIODRAIN
 - copy data out of request buffers to satisfy a write request
STRIPE_OP_RECONSTRUCT
 - recalculate parity for new data that has entered the cache
STRIPE_OP_CHECK
 - verify that the parity is correct

The flow is the same as in the RAID-5 case, and reuses some routines, namely:
1/ ops_complete_postxor (renamed to ops_complete_reconstruct)
2/ ops_complete_compute (updated to set up to 2 targets uptodate)
3/ ops_run_check (renamed to ops_run_check_p for xor parity checks)

[neilb@suse.de: fixes to get it to pass mdadm regression suite]
Reviewed-by: Andre Noll <maan@systemlinux.org>
Signed-off-by: Yuri Tikhonov <yur@emcraft.com>
Signed-off-by: Ilya Yanok <yanok@emcraft.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

1 files changed, 5 insertions, 3 deletions

diff --git a/drivers/md/raid5.h b/drivers/md/raid5.h
index 75f2c6c4cf90..116d0b44b2a9 100644
--- a/drivers/md/raid5.h
+++ b/drivers/md/raid5.h
@@ -176,7 +176,9 @@
  */
 enum check_states {
         check_state_idle = 0,
-        check_state_run, /* parity check */
+        check_state_run, /* xor parity check */
+        check_state_run_q, /* q-parity check */
+        check_state_run_pq, /* pq dual parity check */
         check_state_check_result,
         check_state_compute_run, /* parity repair */
         check_state_compute_result,
@@ -216,7 +218,7 @@ struct stripe_head {
          * @target - STRIPE_OP_COMPUTE_BLK target
          */
         struct stripe_operations {
-                int                  target;
+                int                  target, target2;
                 enum sum_check_flags zero_sum_result;
         } ops;
         struct r5dev {
@@ -299,7 +301,7 @@ struct r6_state {
 #define STRIPE_OP_COMPUTE_BLK   1
 #define STRIPE_OP_PREXOR        2
 #define STRIPE_OP_BIODRAIN      3
-#define STRIPE_OP_POSTXOR       4
+#define STRIPE_OP_RECONSTRUCT   4
 #define STRIPE_OP_CHECK 5
 
 /*