Btrfs: devid filter

Relocate chunks which have at least one stripe located on a device with
devid X.

Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index eee77fc..7cfec03 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -201,6 +201,7 @@
  */
 #define BTRFS_BALANCE_ARGS_PROFILES	(1ULL << 0)
 #define BTRFS_BALANCE_ARGS_USAGE	(1ULL << 1)
+#define BTRFS_BALANCE_ARGS_DEVID	(1ULL << 2)
 
 struct btrfs_balance_args;
 struct btrfs_balance_control {