block: gendisk integrity wrapper

This is a wrapper for accessing a gendisk's integrity bits.  It allows
the integrity support in MD to be compiled with BLK_DEV_INTEGRITY off.
Signed-off-by: NMartin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

include/linux/blkdev.h

@@ -1022,6 +1022,11 @@ struct blk_integrity *bdev_get_integrity(struct block_device *bdev)
 	return bdev->bd_disk->integrity;
 }
 
+static inline struct blk_integrity *blk_get_integrity(struct gendisk *disk)
+{
+	return disk->integrity;
+}
+
 static inline int blk_integrity_rq(struct request *rq)
 {
 	if (rq->bio == NULL)
@@ -1036,6 +1041,7 @@ static inline int blk_integrity_rq(struct request *rq)
 #define blk_rq_count_integrity_sg(a)		(0)
 #define blk_rq_map_integrity_sg(a, b)		(0)
 #define bdev_get_integrity(a)			(0)
+#define blk_get_integrity(a)			(0)
 #define blk_integrity_compare(a, b)		(0)
 #define blk_integrity_register(a, b)		(0)
 #define blk_integrity_unregister(a)		do { } while (0);