linux-kernel - Re: [PATCH v2] asm-generic: fix variable 'p4d' set but not used

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Message-ID: <CAK8P3a12VZHvX+rTDYenONwjBDbBvi2cT-FaqBcTpHbX8Gz4Bg@mail.gmail.com>
Date:   Wed, 7 Aug 2019 09:30:26 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Qian Cai <cai@....pw>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Michal Hocko <mhocko@...e.com>, Jason Gunthorpe <jgg@...pe.ca>,
        Linux-MM <linux-mm@...ck.org>,
        linux-arch <linux-arch@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] asm-generic: fix variable 'p4d' set but not used

On Wed, Aug 7, 2019 at 1:29 AM Qian Cai <cai@....pw> wrote:
>
> A compiler throws a warning on an arm64 system since the
> commit 9849a5697d3d ("arch, mm: convert all architectures to use
> 5level-fixup.h"),
>
> mm/kasan/init.c: In function 'kasan_free_p4d':
> mm/kasan/init.c:344:9: warning: variable 'p4d' set but not used
> [-Wunused-but-set-variable]
>  p4d_t *p4d;
>         ^~~
>
> because p4d_none() in "5level-fixup.h" is compiled away while it is a
> static inline function in "pgtable-nopud.h". However, if converted
> p4d_none() to a static inline there, powerpc would be unhappy as it
> reads those in assembler language in
> "arch/powerpc/include/asm/book3s/64/pgtable.h", so it needs to skip
> assembly include for the static inline C function. While at it,
> converted a few similar functions to be consistent with the ones in
> "pgtable-nopud.h".
>
> Signed-off-by: Qian Cai <cai@....pw>

Acked-by: Arnd Bergmann <arnd@...db.de>