Re: crisv32 runtime failure in -next due to 'page-flags: define behavior SL*B-related flags on compound pages'

[Guenter Roeck]

On 09/21/2015 08:34 AM, Kirill A. Shutemov wrote:
> Guenter Roeck wrote:
> > On 09/18/2015 07:53 AM, Jesper Nilsson wrote:
> > > On Fri, Sep 18, 2015 at 05:25:07PM +0300, Kirill A. Shutemov wrote:
> > > > On Thu, Sep 17, 2015 at 09:29:27AM -0700, Guenter Roeck wrote:
> > > > > Hi,
> > > > >
> > > > > my crisv32 qemu test fails with next-20150917 as follows.
> > > > >
> > > > > NET: Registered protocol family 16
> > > > > kernel BUG at mm/slab.c:1648!
> > > > > Linux 4.3.0-rc1-next-20150917 #1 Wed Sep 16 23:56:59 PDT 2015
> > > > > Oops: 0000
> > > > >
> > > > > [ register dump follows ]
> > > > >
> > > > > See http://server.roeck-us.net:8010/builders/qemu-crisv32-next/builds/83/steps/qemubuildcommand/logs/stdio
> > > > > for a complete log.
> > > >
> > > > Is there a chance to get proper backtrace?
> > >
> > > Yes, it should be possible with CONFIG_KALLSYMS=y in the kconfig.
> >
> > Good to know. I added it to my configuration.
> >
> > Here it is:
> >
> > kernel BUG at mm/slab.c:1648!
>
> I still don't understand what's going on :(
> Could you try with this instrumentation:
>
> diff --git a/mm/slab.c b/mm/slab.c
> index ce9c6531e6f7..10035d1a06d3 100644
> --- a/mm/slab.c
> +++ b/mm/slab.c
> @@ -1645,7 +1645,11 @@ static void kmem_freepages(struct kmem_cache *cachep, struct page *page)
>                  sub_zone_page_state(page_zone(page),
>                                  NR_SLAB_UNRECLAIMABLE, nr_freed);
>
> -       BUG_ON(!PageSlab(page));
> +       if (!PageSlab(page)) {
> +               dump_page(page, "page");
> +               dump_page(compound_head(page), "compound_head(page)");
> +               BUG();
> +       }
>          __ClearPageSlabPfmemalloc(page);
>          __ClearPageSlab(page);
>          page_mapcount_reset(page);

page:c04a5340 count:1 mapcount:1 mapping:c1f34080 index:0xc1f34060
flags: 0x80(slab)
page dumped because: page
page:c1f17a04 count:0 mapcount:1 mapping:00d13600 index:0xc0
flags: 0x0()
page dumped because: compound_head(page)

Does that help ?

Guenter

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