ocfs2: sparse b-tree support

Introduce tree rotations into the b-tree code. This will allow ocfs2 to
support sparse files. Much of the added code is designed to be generic (in
the ocfs2 sense) so that it can later be re-used to implement large
extended attributes.

This patch only adds the rotation code and does minimal updates to callers
of the extent api.

Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>
diff --git a/fs/ocfs2/file.h b/fs/ocfs2/file.h
index cc973f0..e2f6551 100644
--- a/fs/ocfs2/file.h
+++ b/fs/ocfs2/file.h
@@ -39,6 +39,7 @@
 };
 int ocfs2_do_extend_allocation(struct ocfs2_super *osb,
 			       struct inode *inode,
+			       u32 *cluster_start,
 			       u32 clusters_to_add,
 			       struct buffer_head *fe_bh,
 			       handle_t *handle,