linux-kernel - Re: BUG: MAX_LOCKDEP_CHAIN

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Message-ID: <20230125171517.GV11562@twin.jikos.cz>
Date:   Wed, 25 Jan 2023 18:15:17 +0100
From:   David Sterba <dsterba@...e.cz>
To:     Mikhail Gavrilov <mikhail.v.gavrilov@...il.com>
Cc:     dsterba@...e.cz, Btrfs BTRFS <linux-btrfs@...r.kernel.org>,
        Linux List Kernel Mailing <linux-kernel@...r.kernel.org>,
        Chris Murphy <lists@...orremedies.com>
Subject: Re: BUG: MAX_LOCKDEP_CHAIN_HLOCKS too low!

On Wed, Jan 25, 2023 at 01:27:48AM +0500, Mikhail Gavrilov wrote:
> On Tue, Jul 26, 2022 at 9:47 PM David Sterba <dsterba@...e.cz> wrote:
> >
> > On Tue, Jul 26, 2022 at 05:32:54PM +0500, Mikhail Gavrilov wrote:
> > > Hi guys.
> > > Always with intensive writing on a btrfs volume, the message "BUG:
> > > MAX_LOCKDEP_CHAIN_HLOCKS too low!" appears in the kernel logs.
> >
> > Increase the config value of LOCKDEP_CHAINS_BITS, default is 16, 18
> > tends to work.
> 
> Hi,
> Today I was able to get the message "BUG: MAX_LOCKDEP_CHAIN_HLOCKS too
> low!" again even with LOCKDEP_CHAINS_BITS=18 and kernel 6.2-rc5.
> 
> ❯ cat /boot/config-`uname -r` | grep LOCKDEP_CHAINS_BITS
> CONFIG_LOCKDEP_CHAINS_BITS=18
> 
> [88685.088099] BUG: MAX_LOCKDEP_CHAIN_HLOCKS too low!
> [88685.088124] turning off the locking correctness validator.
> [88685.088133] Please attach the output of /proc/lock_stat to the bug report
> [88685.088142] CPU: 14 PID: 1749746 Comm: mv Tainted: G        W    L
>   -------  ---  6.2.0-0.rc5.20230123git2475bf0250de.38.fc38.x86_64 #1
> [88685.088154] Hardware name: System manufacturer System Product
> Name/ROG STRIX X570-I GAMING, BIOS 4408 10/28/2022
> 
> What's next? Increase this value to 19?

Yes, though increasing the value is a workaround so you may see the
warning again.