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/aops.c b/fs/ocfs2/aops.c
index 9db9d64..33e03c5 100644
--- a/fs/ocfs2/aops.c
+++ b/fs/ocfs2/aops.c
@@ -1712,7 +1712,7 @@
 		goto out;
 	} else if (ret == 1) {
 		ret = ocfs2_refcount_cow(inode, di_bh,
-					 wc->w_cpos, wc->w_clen);
+					 wc->w_cpos, wc->w_clen, UINT_MAX);
 		if (ret) {
 			mlog_errno(ret);
 			goto out;