linux-ext4 - Re: [Bug 216529] New: [fstests generic/048] BUG: Kernel NULL pointer dereference at 0x00000069, filemap_release

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Date:   Mon, 10 Oct 2022 22:31:33 +0530
From:   "Ritesh Harjani (IBM)" <ritesh.list@...il.com>
To:     Theodore Ts'o <tytso@....edu>
Cc:     bugzilla-daemon@...nel.org, linux-ext4@...r.kernel.org
Subject: Re: [Bug 216529] New: [fstests generic/048] BUG: Kernel NULL pointer
 dereference at 0x00000069, filemap_release_folio+0x88/0xb0

On 22/09/27 11:40PM, Ritesh Harjani (IBM) wrote:
> On 22/09/26 01:02AM, Theodore Ts'o wrote:
> > On Sun, Sep 25, 2022 at 11:55:29AM +0000, bugzilla-daemon@...nel.org wrote:
> > > https://bugzilla.kernel.org/show_bug.cgi?id=216529
> > >
> > >
> > > Hit a panic on ppc64le, by running generic/048 with 1k block size:
> >
> > Hmm, does this reproduce reliably for you?  I test with a 1k block
> > size on x86_64 as a proxy 4k block sizes on PPC64, where the blocksize
> > < pagesize... and this isn't reproducing for me on x86, and I don't
> > have access to a PPC64LE system.
> >
> > Ritesh, is this something you can take a look at it?  Thanks!
>
> I was away for some personal work for last few days, but I am back to work from
> today. Sure, I will take a look at this and will get back.
>
> I did give this test a couple of runs though, but wasn't able to reproduce it.
> But let me try few more things along with more iterations. Will update
> accordingly.

I thought I had updated this. But I guess I forgot to update on this mail
thread...

I tested this for quite some time in a loop and also gave it a overnight run,
but I couldn't hit this issue. I had kept low memory size guest, so that we
could see more reclaim activity (which I also ensured by doing perf trace to see
if we are going over that path or not while test was running).

I am not sure whether this could be a timing issue or what. Maybe if you could
share your defconfig, I could give a try with that on my setup once.

-ritesh