syzbot has bisected this bug to:

commit 867c90eeea9d81ad1336881b61a4dcf692fc5d50
Author: Stephen Rothwell [off-list ref]
Date:   Mon Jul 8 00:22:38 2019 +0000

     Merge remote-tracking branch 'xfs/for-next'

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=16c69bc3a00000
start commit:   d58b5ab9 Add linux-next specific files for 20190708
git tree:       linux-next
final crash:    https://syzkaller.appspot.com/x/report.txt?x=15c69bc3a00000
console output: https://syzkaller.appspot.com/x/log.txt?x=11c69bc3a00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=bf9882946ecc11d9
dashboard link: https://syzkaller.appspot.com/bug?extid=f70e9b00f8c7d4187bd0
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=173375c7a00000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1536f9bfa00000

Reported-by: syzbot+f70e9b00f8c7d4187bd0@syzkaller.appspotmail.com
Fixes: 867c90eeea9d ("Merge remote-tracking branch 'xfs/for-next'")

For information about bisection process see: https://goo.gl/tpsmEJ#bisection