linux-kernel - Re: [PATCH v2] xtensa: remove redundant flush_dcache_page and ARCH_IMPLEMENTS_FLUSH_DCACHE

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Date: Sat, 27 Apr 2024 12:05:16 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: Barry Song <21cnbao@...il.com>
Cc: chris@...kel.net, jcmvbkbc@...il.com, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org, willy@...radead.org,
	dennis@...nel.org, alexghiti@...osinc.com,
	Barry Song <v-songbaohua@...o.com>,
	Huacai Chen <chenhuacai@...ngson.cn>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	kernel test robot <lkp@...el.com>
Subject: Re: [PATCH v2] xtensa: remove redundant flush_dcache_page and
 ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE macros

Hi,

On Tue, Mar 19, 2024 at 02:09:20PM +1300, Barry Song wrote:
> From: Barry Song <v-songbaohua@...o.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' [-Wunused-variable]
>      174 |                         struct page *dst_page = sg_page(req->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@...ngson.cn>
> Cc: Herbert Xu <herbert@...dor.apana.org.au>
> Reported-by: kernel test robot <lkp@...el.com>
> Closes: https://lore.kernel.org/oe-kbuild-all/202403091614.NeUw5zcv-lkp@intel.com/
> Reported-by: Barry Song <v-songbaohua@...o.com>
> Closes: https://lore.kernel.org/all/CAGsJ_4yDk1+axbte7FKQEwD7X2oxUCFrEc9M5YOS1BobfDFXPA@mail.gmail.com/
> Reported-by: Guenter Roeck <linux@...ck-us.net>
> Closes: https://lore.kernel.org/all/aaa8b7d7-5abe-47bf-93f6-407942436472@roeck-us.net/
> Fixes: 77292bb8ca69 ("crypto: scomp - remove memcpy if sg_nents is 1 and pages are lowmem")
> Signed-off-by: Barry Song <v-songbaohua@...o.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=unused-variable]
  174 |                         struct page *dst_page = sg_page(req->dst);

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 ?

Thanks,
Guenter