ocfs2: CoW a reflinked cluster when it is truncated.

When we truncate a file to a specific size which resides in a reflinked
cluster, we need to CoW it since ocfs2_zero_range_for_truncate will
zero the space after the size(just another type of write).

So we add a "max_cpos" in ocfs2_refcount_cow so that it will stop when
it hit the max cluster offset.

Signed-off-by: Tao Ma <tao.ma@oracle.com>
diff --git a/fs/ocfs2/refcounttree.h b/fs/ocfs2/refcounttree.h
index a8c15b0..356f99c 100644
--- a/fs/ocfs2/refcounttree.h
+++ b/fs/ocfs2/refcounttree.h
@@ -53,5 +53,5 @@
 					  int *credits,
 					  struct ocfs2_alloc_context **meta_ac);
 int ocfs2_refcount_cow(struct inode *inode, struct buffer_head *di_bh,
-		       u32 cpos, u32 write_len);
+		       u32 cpos, u32 write_len, u32 max_cpos);
 #endif /* OCFS2_REFCOUNTTREE_H */