Re: [PATCH v13] mm: report per-page metadata information

[Pasha Tatashin]

On Tue, Aug 6, 2024 at 4:53 PM Ira Weiny <iweiny@iweiny-mobl> wrote:
>
> On Tue, Aug 06, 2024 at 01:59:54PM -0400, Pasha Tatashin wrote:
> > On Mon, Aug 5, 2024 at 7:06 PM Dan Williams <dan.j.williams@xxxxxxxxx> wrote:
> > >
> > > Pasha Tatashin wrote:
> > > [..]
> > > > Thank you for the heads up. Can you please attach a full config file,
> > > > also was anyone able to reproduce this problem in qemu with emulated
> > > > nvdimm?
> > >
> > > Yes, I can reproduce the crash just by trying to reconfigure the mode of
> > > a pmem namespace:
> > >
> > > # ndctl create-namespace -m raw -f -e namespace0.0
> > >
> > > ...where namespace0.0 results from:
> > >
> > >     memmap=4G!4G
> > >
> > > ...passed on the kernel command line.
> > >
> > > Kernel config here:
> > >
> > > https://gist.github.com/djbw/143705077103d43a735c179395d4f69a
> >
> > Excellent, I was able to reproduce this problem.
> >
> > The problem appear to be caused by this code:
> >
> > Calling page_pgdat() in depopulate_section_memmap():
> >
> > static void depopulate_section_memmap(unsigned long pfn, unsigned long nr_pages,
> >                 struct vmem_altmap *altmap)
> > {
> >         unsigned long start = (unsigned long) pfn_to_page(pfn);
> >         unsigned long end = start + nr_pages * sizeof(struct page);
> >
> >         mod_node_page_state(page_pgdat(pfn_to_page(pfn)), NR_MEMMAP,
> > <<<< We cannot do it.
> >                             -1L * (DIV_ROUND_UP(end - start, PAGE_SIZE)));
> >         vmemmap_free(start, end, altmap);
> > }
> >
> > The page_pgdat() returns NULL starting from:
> > pageunmap_range()
> >     remove_pfn_range_from_zone() <- page is removed from the zone.
>
> Is there any idea on a fix?  I'm seeing the same error.
>
> [  561.867431]  ? mod_node_page_state+0x11/0xa0
> [  561.867963]  section_deactivate+0x2a0/0x2c0
> [  561.868496]  __remove_pages+0x59/0x90
> [  561.868975]  arch_remove_memory+0x1a/0x40
> [  561.869491]  memunmap_pages+0x206/0x3d0
> [  561.869972]  devres_release_all+0xa8/0xe0
> [  561.870466]  device_unbind_cleanup+0xe/0x70
> [  561.870960]  device_release_driver_internal+0x1ca/0x210
> [  561.871529]  driver_detach+0x47/0x90
> [  561.871981]  bus_remove_driver+0x6c/0xf0
>
> Shall we revert this patch until we figure out a fix?

I am working on a fix, and will send it out in a couple hours.

Pasha