ext4: trace punch_hole correctly in ext4_ext_map_blocks

When ext4_ext_map_blocks() is called by punch_hole, trace should
trace blocks punched out.

Signed-off-by: Yongqiang Yang <xiaoqiangnk@gmail.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

fs/ext4/extents.c

@@ -4171,12 +4171,12 @@ out2:
 		ext4_ext_drop_refs(path);
 		kfree(path);
 	}
-	trace_ext4_ext_map_blocks_exit(inode, map->m_lblk,
-		newblock, map->m_len, err ? err : allocated);
-
 	result = (flags & EXT4_GET_BLOCKS_PUNCH_OUT_EXT) ?
 			punched_out : allocated;
 
+	trace_ext4_ext_map_blocks_exit(inode, map->m_lblk,
+		newblock, map->m_len, err ? err : result);
+
 	return err ? err : result;
 }