linux-kernel - Re: compaction: VM_BUG_ON_PAGE(!zone_spans_pfn(page

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Date:   Sun, 26 Apr 2020 17:41:39 +0300
From:   Mike Rapoport <rppt@...ux.ibm.com>
To:     Qian Cai <cai@....pw>
Cc:     Mel Gorman <mgorman@...e.de>, Vlastimil Babka <vbabka@...e.cz>,
        Michal Hocko <mhocko@...nel.org>,
        David Hildenbrand <david@...hat.com>,
        Linux-MM <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>, Baoquan He <bhe@...hat.com>
Subject: Re: compaction: VM_BUG_ON_PAGE(!zone_spans_pfn(page_zone(page), pfn))

Hi,

On Thu, Apr 23, 2020 at 05:25:56PM -0400, Qian Cai wrote:
> Compaction starts to crash below on linux-next today. The faulty page belongs to Node 0 DMA32 zone.
> I’ll continue to narrow it down, but just want to give a headup in case someone could beat me to it.
> 
> Debug output from free_area_init_core()
> [    0.000000] KK start page = ffffea0000000040, end page = ffffea0000040000, nid = 0 DMA
> [    0.000000] KK start page = ffffea0000040000, end page = ffffea0004000000, nid = 0 DMA32
> [    0.000000] KK start page = ffffea0004000000, end page = ffffea0012000000, nid = 0 NORMAL
> [    0.000000] KK start page = ffffea0012000000, end page = ffffea0021fc0000, nid = 4 NORMAL
> 
> I don’t understand how it could end up in such a situation. There are several recent patches look
> more related than some others.

Can you please add "mminit_loglevel=4 memblock=debug" to the kernel
command line?

> - mm: rework free_area_init*() funcitons
> https://lore.kernel.org/linux-mm/20200412194859.12663-1-rppt@kernel.org/
> Could this somehow allow an invalid pfn to escape into the page allocator?
> Especially, is it related to skip the checks in memmap_init_zone()?
> https://lore.kernel.org/linux-mm/20200412194859.12663-16-rppt@kernel.org


-- 
Sincerely yours,
Mike.