block: Add BLKROTATIONAL ioctl

Introduce an ioctl which permits applications to query whether a block
device is rotational.

Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/block/ioctl.c b/block/ioctl.c
index ca939fc..337d207 100644
--- a/block/ioctl.c
+++ b/block/ioctl.c
@@ -278,6 +278,8 @@
 		return put_uint(arg, bdev_discard_zeroes_data(bdev));
 	case BLKSECTGET:
 		return put_ushort(arg, queue_max_sectors(bdev_get_queue(bdev)));
+	case BLKROTATIONAL:
+		return put_ushort(arg, !blk_queue_nonrot(bdev_get_queue(bdev)));
 	case BLKRASET:
 	case BLKFRASET:
 		if(!capable(CAP_SYS_ADMIN))