commit edf064e7c6fec3646b06c944a8e35d1a3de5c2c3 (HEAD, refs/bisect/bad)
Author: Goldwyn Rodrigues <rgoldwyn@suse.com>
Date:   Tue Jun 20 07:05:49 2017 -0500

    btrfs: nowait aio support

apparently breaks several shell related features on my system.
In zsh history stopped working, because no new entries are added
anymore.
I fist noticed the issue when I tried to build mplayer. It uses a shell
script to generate a help_mp.h file:

  % help/help_create.sh help/help_mp-en.h UTF-8

This file gets corrupted:

--- help_mp_good.h      2017-07-04 05:38:33.161640826 +0200
+++ help_mp_bad.h       2017-07-04 05:51:00.650730726 +0200
@@ -1,14 +1,8 @@
-/* WARNING! This is a generated file, do NOT edit.
- * See the help/ subdirectory for the editable files. */
 
 -#ifndef MPLAYER_HELP_MP_H
 -#define MPLAYER_HELP_MP_H
 -
 -#include <inttypes.h>
 -#include "config.h"
 +#endif /* MPLAYER_HELP_MP_H */
 +he English master file */
  
  -// $Revision: 37846 $
  -// MASTER FILE. Use this file as base for translations.
  + for translations.
...
(I have attached the testcase.)

/dev/sdc3 on / type btrfs (rw,noatime,lazytime,compress=lzo,ssd,noacl,space_cache=v2,subvolid=5,subvol=/) 
 # cat /sys/block/sdc/queue/scheduler
[none] mq-deadline 

-- 
Markus