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, 4 insertions, 0 deletions

diff --git a/drivers/md/Kconfig b/drivers/md/Kconfig
index 2281b5098e95..449d0b9cac14 100644
--- a/drivers/md/Kconfig
+++ b/drivers/md/Kconfig
@@ -121,6 +121,7 @@ config MD_RAID10
 config MD_RAID456
         tristate "RAID-4/RAID-5/RAID-6 mode"
         depends on BLK_DEV_MD
+        select MD_RAID6_PQ
         select ASYNC_MEMCPY
         select ASYNC_XOR
         ---help---
@@ -180,6 +181,9 @@ config MD_RAID5_RESHAPE
 
           If unsure, say Y.
 
+config MD_RAID6_PQ
+        tristate
+
 config MD_MULTIPATH
         tristate "Multipath I/O support"
         depends on BLK_DEV_MD