linux-ext4 - Re: next: kernel BUG at fs/ext4/mballoc.c:4369!

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Date:   Tue, 18 Jul 2023 17:17:52 +0530
From:   Naresh Kamboju <naresh.kamboju@...aro.org>
To:     "Theodore Ts'o" <tytso@....edu>
Cc:     Ritesh Harjani <ritesh.list@...il.com>,
        open list <linux-kernel@...r.kernel.org>,
        linux-mm <linux-mm@...ck.org>, lkft-triage@...ts.linaro.org,
        linux-ext4 <linux-ext4@...r.kernel.org>,
        LTP List <ltp@...ts.linux.it>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Arnd Bergmann <arnd@...db.de>,
        Dan Carpenter <dan.carpenter@...aro.org>,
        Andreas Dilger <adilger.kernel@...ger.ca>,
        Ojaswin Mujoo <ojaswin@...ux.ibm.com>
Subject: Re: next: kernel BUG at fs/ext4/mballoc.c:4369!

On Tue, 18 Jul 2023 at 03:04, Theodore Ts'o <tytso@....edu> wrote:
>
> On Mon, Jul 17, 2023 at 08:04:54PM +0530, Ritesh Harjani wrote:
> >
> > These can basically trigger in extremely low memory space and only when
> > such ranges exist in the PA rbtree. Hence, I guess it is a little hard
> > to tigger race.
>
> Ritesh, thanks for looking into this!
>
> Naresh, how easy is it for you to trigger the BUG when using LTP?  I
> did two xfstests runs using "gce-xfstests -c ext2/default -g auto",
> one on the ext4 dev branch, and one on linux-next 20230717, and I
> wasn't able to trigger the BUG.
>
> If you can trivially trigger it using LTP (perhaps with a low memory
> configuration in your test setup?), that would be useful to know.

In our setup it is not easy to reproduce with the same device and
same build on x86_4 and arm64 juno-r2 connected with SSD drive
and running LTP fs testing.

LTP fs_fill is triggering several ENOSPC before getting this reported
kernel BUG at fs/ext4/mballoc.c:4369!

The reported issues are not noticed on latest Linux next tags.

- Naresh

>
> Cheers,
>
>                                         - Ted