Re: kernel oops on mmotm-2015-10-15-15-20

[Minchan Kim <minchan@kernel.org>]

Hello Hugh,

On Wed, Oct 21, 2015 at 05:59:59PM -0700, Hugh Dickins wrote:
> On Thu, 22 Oct 2015, Minchan Kim wrote:
> > 
> > I added the code to check it and queued it again but I had another oops
> > in this time but symptom is related to anon_vma, too.
> > (kernel is based on recent mmotm + unconditional mkdirty for bug fix)
> > It seems page_get_anon_vma returns NULL since the page was not page_mapped
> > at that time but second check of page_mapped right before try_to_unmap seems
> > to be true.
> > 
> > Adding 4191228k swap on /dev/vda5.  Priority:-1 extents:1 across:4191228k FS
> > Adding 4191228k swap on /dev/vda5.  Priority:-1 extents:1 across:4191228k FS
> > page:ffffea0001cfbfc0 count:3 mapcount:1 mapping:ffff88007f1b5f51 index:0x600000aff
> > flags: 0x4000000000048019(locked|uptodate|dirty|swapcache|swapbacked)
> > page dumped because: VM_BUG_ON_PAGE(PageAnon(page) && !PageKsm(page) && !anon_vma)
> 
> That's interesting, that's one I added in my page migration series.
> Let me think on it, but it could well relate to the one you got before.

I will roll back to mm/madv_free-v4.3-rc5-mmotm-2015-10-15-15-20
instead of next-20151021 to remove noise from your migration cleanup
series and will test it again.
If it is fixed, I will test again with your migration patchset, then.

> 
> > page->mem_cgroup:ffff88007f3dcc00
> > ------------[ cut here ]------------
> > kernel BUG at mm/migrate.c:889!
> > invalid opcode: 0000 [#1] SMP 
> > Dumping ftrace buffer:
> >    (ftrace buffer empty)
> > Modules linked in:
> > CPU: 11 PID: 59 Comm: khugepaged Not tainted 4.3.0-rc6-next-20151021-THP-ref-madv_free+ #1557
> 
> Hmm, it might be me to blame, or it might be Kirill, don't know yet.

It might be me, either.

> 
> Oh, hold on, I think Andrew has just posted a new mmotm, and it includes
> an update to Kirill's migrate_pages-try-to-split-pages-on-queueing.patch:
> I haven't digested yet, but it might turn out to be relevant.
> 
> Hugh

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