Re: [syzbot] [btrfs?] BUG: MAX_LOCKDEP_CHAIN_HLOCKS too low! (6)

From: Josef Bacik
Date: Wed Aug 21 2024 - 16:13:50 EST


On Wed, Aug 21, 2024 at 12:45:25PM -0700, syzbot wrote:
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: 5c43d43bad35 Merge branches 'for-next/acpi', 'for-next/mis..
> git tree: git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci
> console output: https://syzkaller.appspot.com/x/log.txt?x=13471a05980000
> kernel config: https://syzkaller.appspot.com/x/.config?x=c91f83ae59feaa1f
> dashboard link: https://syzkaller.appspot.com/bug?extid=dfb6eff2a68b42d557d3
> compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
> userspace arch: arm64
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=10efded5980000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=12e94093980000
>
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/cc2dd4be620e/disk-5c43d43b.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/81d40d99ddbf/vmlinux-5c43d43b.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/bc6aed0f2bc5/Image-5c43d43b.gz.xz
> mounted in repro: https://storage.googleapis.com/syzbot-assets/d55321fffedc/mount_0.gz
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+dfb6eff2a68b42d557d3@xxxxxxxxxxxxxxxxxxxxxxxxx
>
> BUG: MAX_LOCKDEP_CHAIN_HLOCKS too low!

Can we disable syzbot issues for this specific error? Btrfs uses lockdep
annotations for our tree locks, so we _easily_ cross this threshold on the
default configuration. Our CI config requires the following settings to get
lockdep to work longer than two or three tests

CONFIG_LOCKDEP_BITS=20
CONFIG_LOCKDEP_CHAINS_BITS=20
CONFIG_LOCKDEP_STACK_TRACE_BITS=19
CONFIG_LOCKDEP_STACK_TRACE_HASH_BITS=14
CONFIG_LOCKDEP_CIRCULAR_QUEUE_BITS=12

but there's no way to require that in our config (nor do I think we should
really be able to tbqh). It makes more sense for syzbot to just ignore this
particular error as it's not actually a bug. Thanks,

Josef