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Enhance performance by adding sequential stream detection for RAID5/RAID6
sequential write requests. Reduce stripe lock contention with full-stripe
write operations.

There is one common stripe lock for each RAID volume that can be set by
either the RAID engine or the AIO engine. The AIO path has I/O request
sizes well below the stripe size resulting in many Read-Modify-Write
operations.

Sending the request to the RAID engine allows for coalescing requests into
full stripe operations resulting in reduced Read-Modify-Write operations.

Link: https://lore.kernel.org/r/161549375693.25025.2962141451773219796.stgit@brunhilda

Reviewed-by: Scott Benesh <scott.benesh@microchip.com>
Reviewed-by: Mike McGowen <mike.mcgowen@microchip.com>
Reviewed-by: Scott Teel <scott.teel@microchip.com>
Reviewed-by: Kevin Barnett <kevin.barnett@microchip.com>
Signed-off-by: Don Brace <don.brace@microchip.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>