Btrfs: Throttle file_write when data=ordered is flushing the inode

Signed-off-by: Chris Mason <chris.mason@oracle.com>
diff --git a/fs/btrfs/btrfs_inode.h b/fs/btrfs/btrfs_inode.h
index fe6ef8e..5ba8389 100644
--- a/fs/btrfs/btrfs_inode.h
+++ b/fs/btrfs/btrfs_inode.h
@@ -31,6 +31,7 @@
 	struct extent_io_tree io_tree;
 	struct extent_io_tree io_failure_tree;
 	struct inode vfs_inode;
+	atomic_t ordered_writeback;
 
 	u64 ordered_trans;
 	/*