Btrfs: Add new ioctl to add devices

Signed-off-by: Chris Mason <chris.mason@oracle.com>
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index ac7106e..b9257b3 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -551,6 +551,8 @@
 	u64 data_alloc_profile;
 	u64 metadata_alloc_profile;
 	u64 system_alloc_profile;
+
+	void *bdev_holder;
 };
 
 /*