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In-Reply-To: <0df6028c-3e7d-461c-85bd-8ba1bf06e2a6@roeck-us.net>
From: Max Filippov <jcmvbkbc@gmail.com>
Date: Sun, 28 Apr 2024 22:09:49 -0700
Message-ID: <CAMo8BfJTutHPByNZcpjb-2xeUX-Nu2XkjN0DWE6w5xV=zg__Kg@mail.gmail.com>
Subject: Re: [PATCH v2] xtensa: remove redundant flush_dcache_page and
 ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE macros
To: Guenter Roeck <linux@roeck-us.net>
Cc: Barry Song <21cnbao@gmail.com>, chris@zankel.net, akpm@linux-foundation.org, 
	linux-kernel@vger.kernel.org, willy@infradead.org, dennis@kernel.org, 
	alexghiti@rivosinc.com, Barry Song <v-songbaohua@oppo.com>, 
	Huacai Chen <chenhuacai@loongson.cn>, Herbert Xu <herbert@gondor.apana.org.au>, 
	kernel test robot <lkp@intel.com>
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On Sat, Apr 27, 2024 at 12:05=E2=80=AFPM Guenter Roeck <linux@roeck-us.net>=
 wrote:
>
> Hi,
>
> On Tue, Mar 19, 2024 at 02:09:20PM +1300, Barry Song wrote:
> > From: Barry Song <v-songbaohua@oppo.com>
> >
> > xtensa's flush_dcache_page() can be a no-op sometimes. There is a
> > generic implementation for this case in include/asm-generic/
> > cacheflush.h.
> >  #ifndef ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE
> >  static inline void flush_dcache_page(struct page *page)
> >  {
> >  }
> >
> >  #define ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE 0
> >  #endif
> >
> > So remove the superfluous flush_dcache_page() definition, which also
> > helps silence potential build warnings complaining the page variable
> > passed to flush_dcache_page() is not used.
> >
> >    In file included from crypto/scompress.c:12:
> >    include/crypto/scatterwalk.h: In function 'scatterwalk_pagedone':
> >    include/crypto/scatterwalk.h:76:30: warning: variable 'page' set but=
 not used [-Wunused-but-set-variable]
> >       76 |                 struct page *page;
> >          |                              ^~~~
> >    crypto/scompress.c: In function 'scomp_acomp_comp_decomp':
> > >> crypto/scompress.c:174:38: warning: unused variable 'dst_page' [-Wun=
used-variable]
> >      174 |                         struct page *dst_page =3D sg_page(re=
q->dst);
> >          |
> >
> > The issue was originally reported on LoongArch by kernel test
> > robot (Huacai fixed it on LoongArch), then reported by Guenter
> > and me on xtensa.
> >
> > This patch also removes lots of redundant macros which have
> > been defined by asm-generic/cacheflush.h.
> >
> > Cc: Huacai Chen <chenhuacai@loongson.cn>
> > Cc: Herbert Xu <herbert@gondor.apana.org.au>
> > Reported-by: kernel test robot <lkp@intel.com>
> > Closes: https://lore.kernel.org/oe-kbuild-all/202403091614.NeUw5zcv-lkp=
@intel.com/
> > Reported-by: Barry Song <v-songbaohua@oppo.com>
> > Closes: https://lore.kernel.org/all/CAGsJ_4yDk1+axbte7FKQEwD7X2oxUCFrEc=
9M5YOS1BobfDFXPA@mail.gmail.com/
> > Reported-by: Guenter Roeck <linux@roeck-us.net>
> > Closes: https://lore.kernel.org/all/aaa8b7d7-5abe-47bf-93f6-40794243647=
2@roeck-us.net/
> > Fixes: 77292bb8ca69 ("crypto: scomp - remove memcpy if sg_nents is 1 an=
d pages are lowmem")
> > Signed-off-by: Barry Song <v-songbaohua@oppo.com>
>
> The mainline kernel still fails to build xtensa:allmodconfig.
>
> Building xtensa:allmodconfig ... failed
> --------------
> Error log:
> crypto/scompress.c: In function 'scomp_acomp_comp_decomp':
> crypto/scompress.c:174:38: error: unused variable 'dst_page' [-Werror=3Du=
nused-variable]
>   174 |                         struct page *dst_page =3D sg_page(req->ds=
t);
>
> This patch fixes the problem. Is there a chance to get it applied to the
> upstream kernel, or should I just stop build testing xtensa:allmodconfig =
?

Applied to my xtensa tree.
I was still hoping to see rationale for why this is a useful warning.

--=20
Thanks.
-- Max