md/raid6: move raid6 data processing to raid6_pq.ko

Move the raid6 data processing routines into a standalone module
(raid6_pq) to prepare them to be called from async_tx wrappers and other
non-md drivers/modules.  This precludes a circular dependency of raid456
needing the async modules for data processing while those modules in
turn depend on raid456 for the base level synchronous raid6 routines.

To support this move:
1/ The exportable definitions in raid6.h move to include/linux/raid/pq.h
2/ The raid6_call, recovery calls, and table symbols are exported
3/ Extra #ifdef __KERNEL__ statements to enable the userspace raid6test to
   compile

Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: NeilBrown <neilb@suse.de>

1 files changed, 2 insertions, 0 deletions

diff --git a/drivers/md/raid5.h b/drivers/md/raid5.h
index c172371481c7..2934ee0a39c6 100644
--- a/drivers/md/raid5.h
+++ b/drivers/md/raid5.h
@@ -269,6 +269,8 @@ struct r6_state {
 #define READ_MODIFY_WRITE       2
 /* not a write method, but a compute_parity mode */
 #define CHECK_PARITY            3
+/* Additional compute_parity mode -- updates the parity w/o LOCKING */
+#define UPDATE_PARITY           4
 
 /*
  * Stripe state