Re: [syzbot] WARNING in btrfs_space_info_update_bytes_may_use

[Matthew Wilcox]

Dmitry, I don't see a way to tell syzbot that its bisection has gone
astray.  Can you add one or document it if it already exists?

On Mon, Oct 31, 2022 at 04:51:22AM -0700, syzbot wrote:
> syzbot has bisected this issue to:
> 
> commit 0c7c575df56b957390206deb018c41acbb412159
> Author: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
> Date:   Wed Feb 24 20:01:52 2021 +0000
> 
>     mm/filemap: remove dynamically allocated array from filemap_read

This change affects the read path.  The crash happens in the unmount
path.  The data structure that's being checked is modified in the write
path.  I just can't see how this commit is in any way related.

> bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=119e21b6880000
> start commit:   b229b6ca5abb Merge tag 'perf-tools-fixes-for-v6.1-2022-10-..
> git tree:       upstream
> final oops:     https://syzkaller.appspot.com/x/report.txt?x=139e21b6880000
> console output: https://syzkaller.appspot.com/x/log.txt?x=159e21b6880000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=a66c6c673fb555e8
> dashboard link: https://syzkaller.appspot.com/bug?extid=8edfa01e46fd9fe3fbfb
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=17db9ab1880000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=124e21b6880000
> 
> Reported-by: syzbot+8edfa01e46fd9fe3fbfb@xxxxxxxxxxxxxxxxxxxxxxxxx
> Fixes: 0c7c575df56b ("mm/filemap: remove dynamically allocated array from filemap_read")
> 
> For information about bisection process see: https://goo.gl/tpsmEJ#bisection