ocfs2: unmap_mapping_range() in ocfs2_truncate()

We weren't calling this before, but since ocfs2 handles the entire truncate
operation, we should.
Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>

fs/ocfs2/file.c

@@ -326,6 +326,7 @@ static int ocfs2_truncate_file(struct inode *inode,
 		   (unsigned long long)OCFS2_I(inode)->ip_blkno,
 		   (unsigned long long)new_i_size);
 
+	unmap_mapping_range(inode->i_mapping, new_i_size + PAGE_SIZE - 1, 0, 1);
 	truncate_inode_pages(inode->i_mapping, new_i_size);
 
 	fe = (struct ocfs2_dinode *) di_bh->b_data;