Potential regression on kernel 5.19-rc0: kernel BUG at mm/page_table_check.c:51!

Potential regression on kernel 5.19-rc0: kernel BUG at mm/page_table_check.c:51!

[Zorro Lang]

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.

Thanks,
Zorro

Re: Potential regression on kernel 5.19-rc0: kernel BUG at mm/page_table_check.c:51!

[Zorro Lang]

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

> 
> Thanks,
> Zorro

Re: Potential regression on kernel 5.19-rc0: kernel BUG at mm/page_table_check.c:51!

[Dave Chinner]

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@fromorbit.com

Re: Potential regression on kernel 5.19-rc0: kernel BUG at mm/page_table_check.c:51!

[Matthew Wilcox]

On Tue, May 31, 2022 at 08:29:19AM +1000, Dave Chinner wrote:
> On Tue, May 31, 2022 at 02:39:08AM +0800, Zorro Lang wrote:
> > 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'?

You guys know about tools/testing/ktest/config-bisect.pl right?