linux-ext4 - Re: Potential regression on kernel 5.19-rc0: kernel BUG at mm/page_table

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Message-ID: <20220530222919.GA1098723@dread.disaster.area>
Date:   Tue, 31 May 2022 08:29:19 +1000
From:   Dave Chinner <david@...morbit.com>
To:     Zorro Lang <zlang@...hat.com>
Cc:     linux-mm@...ck.org, linux-xfs@...r.kernel.org,
        linux-ext4@...r.kernel.org, nvdimm@...ts.linux.dev
Subject: Re: Potential regression on kernel 5.19-rc0: kernel BUG at
 mm/page_table_check.c:51!

On Tue, May 31, 2022 at 02:39:08AM +0800, Zorro Lang wrote:
> On Mon, May 30, 2022 at 04:06:16PM +0800, Zorro Lang wrote:
> > Hi mm folks:
> > 
> > I reported a regression bug on latest upstream linux:
> > https://bugzilla.kernel.org/show_bug.cgi?id=216047
> > 
> > It's about xfs/ext4 + DAX, panic at mm/page_table_check.c:51!
> > 
> >   static struct page_table_check *get_page_table_check(struct page_ext *page_ext)
> >   {
> > ==>     BUG_ON(!page_ext);
> >         return (void *)(page_ext) + page_table_check_ops.offset;
> >   }
> > 
> > It's 100% reproducible for me, by running fstests generic/623:
> >   https://git.kernel.org/pub/scm/fs/xfs/xfstests-dev.git/tree/tests/generic/623
> > on xfs or ext4 with DAX enabled.
> > 
> > It doesn't look like a xfs or ext4 issue, so send to linux-mm to get more
> > reviewing. More details please refer to above bug link. I changed its Pruduct
> > to mm, but the Assignee isn't changed by default.
> 
> It's not a regression *recently* at least, I still can reproduce this bug on
> linux v5.16.
> 
> But I found it's related with someone kernel configuration (sorry I haven't
> figured out which one config is). I've upload two kernel config files, one[1]
> can build a kernel which reproduce this bug, the other[2] can't. Hope that
> helps.
> 
> Thanks,
> Zorro
> 
> [1]
> https://bugzilla.kernel.org/attachment.cgi?id=301076
> 
> [2]
> https://bugzilla.kernel.org/attachment.cgi?id=301077

Rather than make anyone looking at this download multiple files and
run diff, perhaps you could just post the output of 'diff -u
config.good config.bad'?

Cheers,

Dave.
-- 
Dave Chinner
david@...morbit.com