linux-kernel - Fwd: block/badblocks.c warning in 6.7-rc2

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Date:   Wed, 29 Nov 2023 06:47:20 +0700
From:   Bagas Sanjaya <bagasdotme@...il.com>
To:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux Regressions <regressions@...ts.linux.dev>,
        Linux Block Devices <linux-block@...r.kernel.org>,
        Linux RAID <linux-raid@...r.kernel.org>,
        Linux bcachefs <linux-bcachefs@...r.kernel.org>
Cc:     Coly Li <colyli@...e.de>, Xiao Ni <xni@...hat.com>,
        Geliang Tang <geliang.tang@...e.com>,
        Jens Axboe <axboe@...nel.dk>, Song Liu <song@...nel.org>,
        Kent Overstreet <kent.overstreet@...ux.dev>,
        Janpieter Sollie <janpieter.sollie@...net.be>
Subject: Fwd: block/badblocks.c warning in 6.7-rc2

Hi,

I notice a regression report that is rather well-handled on Bugzilla [1].
Quoting from it:

> 
> when booting from 6.7-rc2, compiled with clang, I get this warning on one of my 3 bcachefs volumes:
> WARNING: CPU: 3 PID: 712 at block/badblocks.c:1284 badblocks_check (block/badblocks.c:1284) 
> The reason why isn't clear, but the stack trace points to an error in md error handling.
> This bug didn't happen in 6.6
> there are 3 commits in 6.7-rc2 which may cause them,
> in attachment:
> - decoded stacktrace of dmesg
> - kernel .config

The culprit author then replied:

> The warning is from this line of code in _badblocks_check(),
> 1284         WARN_ON(bb->shift < 0 || sectors == 0);
> 
> It means the caller sent an invalid range to check. From the oops information,
> "RDX: 0000000000000000" means parameter 'sectors' is 0.
> 
> So the question is, why does md raid code send a 0-length range for badblocks check? Is this behavior on purpose, or improper?
> ...
> IMHO, it doesn't make sense for caller to check a zero-length LBA range. The warning works as expect to detect improper call to badblocks_check().

See Bugzilla for the full thread and attached decoded dmesg and kernel config.

Anyway, I'm adding this regression to regzbot:

#regzbot introduced: 3ea3354cb9f03e https://bugzilla.kernel.org/show_bug.cgi?id=218184
#regzbot title: badblocks_check regression (md error handling) on bcachefs volume

Thanks.

[1]: https://bugzilla.kernel.org/show_bug.cgi?id=218184

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