linux-kernel - Re: arm32: panic in move_freepages (Was [PATCH v2 0/4] arm64: drop pfn_valid_within() and simplify pfn

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Date:   Wed, 12 May 2021 04:50:47 +0100
From:   Matthew Wilcox <willy@...radead.org>
To:     Kefeng Wang <wangkefeng.wang@...wei.com>
Cc:     Mike Rapoport <rppt@...nel.org>,
        linux-arm-kernel@...ts.infradead.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Ard Biesheuvel <ardb@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        David Hildenbrand <david@...hat.com>,
        Marc Zyngier <maz@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Mike Rapoport <rppt@...ux.ibm.com>,
        Will Deacon <will@...nel.org>, kvmarm@...ts.cs.columbia.edu,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: arm32: panic in move_freepages (Was [PATCH v2 0/4] arm64: drop
 pfn_valid_within() and simplify pfn_valid())

On Sun, Apr 25, 2021 at 03:51:56PM +0800, Kefeng Wang wrote:
> we see the PC is at PageLRU, same reason like arm64 panic log,
> 
> "PageBuddy in move_freepages returns false Then we call PageLRU, the macro
> calls PF_HEAD which is compound_page() compound_page reads
> page->compound_head, it is 0xffffffffffffffff, so it resturns
> 0xfffffffffffffffe - and accessing this address causes crash"

Oh.  I posted patches to fix this back in 2018.

https://lore.kernel.org/linux-mm/20180414043145.3953-6-willy@infradead.org/

and 2019.

https://lore.kernel.org/linux-mm/20190501202433.GC28500@bombadil.infradead.org/

and 2020.

https://lore.kernel.org/linux-mm/20200408150148.25290-6-willy@infradead.org/

Looks like it's about that time of year for me to try to fix this again.