linux-kernel - Re: BUG: MAX_LOCKDEP_CHAIN

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Message-Id: <1d1afda7-2b4b-4984-adbe-51339ebbdd18@www.fastmail.com>
Date:   Wed, 03 Aug 2022 16:00:40 -0400
From:   "Chris Murphy" <lists@...orremedies.com>
To:     Михаил Гаврилов 
        <mikhail.v.gavrilov@...il.com>, "David Sterba" <dsterba@...e.cz>,
        "Btrfs BTRFS" <linux-btrfs@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Cc:     "Tetsuo Handa" <penguin-kernel@...ove.sakura.ne.jp>,
        dvyukov@...gle.com
Subject: Re: BUG: MAX_LOCKDEP_CHAIN_HLOCKS too low!



On Wed, Aug 3, 2022, at 3:28 PM, 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.
>
> I confirm that after bumping LOCKDEP_CHAINS_BITS to 18 several days of
> continuous writing on the BTRFS partition with different files with a
> total size of 10Tb I didn't see this kernel bug message again.
> Tetsuo, I saw your commit 5dc33592e95534dc8455ce3e9baaaf3dae0fff82 [1]
> set for LOCKDEP_CHAINS_BITS default value 16.
> Why not increase LOCKDEP_CHAINS_BITS to 18 by default?

This will be making it into Fedora debug kernels, which have lockdep enabled on them, starting with 5.20 series, which are now building in koji.
https://gitlab.com/cki-project/kernel-ark/-/merge_requests/1921




-- 
Chris Murphy