linux-kernel - Re: [PATCH 0/3] Fix build failure with v5.8-rc1

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Date:   Wed, 17 Jun 2020 11:57:08 +0100
From:   Will Deacon <will@...nel.org>
To:     Christophe Leroy <christophe.leroy@...roup.eu>
Cc:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-mm@...ck.org, arnd@...db.de
Subject: Re: [PATCH 0/3] Fix build failure with v5.8-rc1

[+Arnd in case he's interested in this series]

On Mon, Jun 15, 2020 at 12:57:55PM +0000, Christophe Leroy wrote:
> Commit 2ab3a0a02905 ("READ_ONCE: Enforce atomicity for
> {READ,WRITE}_ONCE() memory accesses") leads to following build
> failure on powerpc 8xx.
> 
> To fix it, this small series introduces a new helper named ptep_get()
> to replace the direct access with READ_ONCE(). This new helper
> can be overriden by architectures.

Thanks for doing this, and sorry for the breakage. For the series:

Acked-by: Will Deacon <will@...nel.org>

Hopefully we can introduce accessors for the other page-table levels too,
but that can obviously happen incrementally.

Will

> Christophe Leroy (3):
>   mm/gup: Use huge_ptep_get() in gup_hugepte()
>   mm: Allow arches to provide ptep_get()
>   powerpc/8xx: Provide ptep_get() with 16k pages
> 
>  arch/powerpc/include/asm/nohash/32/pgtable.h | 10 ++++++++++
>  include/asm-generic/hugetlb.h                |  2 +-
>  include/linux/pgtable.h                      |  7 +++++++
>  mm/gup.c                                     |  4 ++--
>  4 files changed, 20 insertions(+), 3 deletions(-)
> 
> -- 
> 2.25.0
>