Re: [PATCH v13] mm: report per-page metadata information
From: Pasha Tatashin
Date: Tue Aug 06 2024 - 17:38:18 EST
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