[PATCH] xtensa: remove redundant flush_dcache_page and ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE macros

[PATCH] xtensa: remove redundant flush_dcache_page and ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE macros

[Barry Song]

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' [-Wunused-variable]
     174 |                         struct page *dst_page = sg_page(req->dst);
         |

The issue was originally reported on LoongArch by kernel test
robot. And Huacai fixed it on LoongArch, but I found xtensa
obviously has the same issue.

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/
Closes: https://lore.kernel.org/all/CAGsJ_4yDk1+axbte7FKQEwD7X2oxUCFrEc9M5YOS1BobfDFXPA@mail.gmail.com/
Signed-off-by: Barry Song <v-songbaohua@oppo.com>
---
 arch/xtensa/include/asm/cacheflush.h | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/arch/xtensa/include/asm/cacheflush.h b/arch/xtensa/include/asm/cacheflush.h
index 38bcecb0e457..11efdc8eb262 100644
--- a/arch/xtensa/include/asm/cacheflush.h
+++ b/arch/xtensa/include/asm/cacheflush.h
@@ -144,9 +144,6 @@ void local_flush_cache_page(struct vm_area_struct *vma,
 #define flush_cache_vmap_early(start,end)		do { } while (0)
 #define flush_cache_vunmap(start,end)			do { } while (0)
 
-#define ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE 0
-#define flush_dcache_page(page)				do { } while (0)
-
 #define flush_icache_range local_flush_icache_range
 #define flush_cache_page(vma, addr, pfn)		do { } while (0)
 #define flush_cache_range(vma, start, end)		do { } while (0)
-- 
2.34.1

Re: [PATCH] xtensa: remove redundant flush_dcache_page and ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE macros

[Guenter Roeck]

On Wed, Mar 13, 2024 at 05:50:36PM +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' [-Wunused-variable]
>      174 |                         struct page *dst_page = sg_page(req->dst);
>          |
> 
> The issue was originally reported on LoongArch by kernel test
> robot. And Huacai fixed it on LoongArch, but I found xtensa
> obviously has the same issue.
> 

Maybe I am doing something wrong, but this patch doesn't build
for me.

 CC      arch/xtensa/kernel/asm-offsets.s
In file included from ./include/linux/highmem.h:8,
                 from ./include/linux/bvec.h:10,
                 from ./include/linux/blk_types.h:10,
                 from ./include/linux/writeback.h:13,
                 from ./include/linux/memcontrol.h:23,
                 from ./include/linux/swap.h:9,
                 from ./include/linux/suspend.h:5,
                 from arch/xtensa/kernel/asm-offsets.c:24:
./include/linux/cacheflush.h:9:5: error: "ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE" is not defined, evaluates to 0 [-Werror=undef]
    9 | #if ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE

Guenter

Re: [PATCH] xtensa: remove redundant flush_dcache_page and ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE macros

[Barry Song]

On Mon, Mar 18, 2024 at 8:16 AM Guenter Roeck <linux@roeck-us.net> wrote:
>
> On Wed, Mar 13, 2024 at 05:50:36PM +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' [-Wunused-variable]
> >      174 |                         struct page *dst_page = sg_page(req->dst);
> >          |
> >
> > The issue was originally reported on LoongArch by kernel test
> > robot. And Huacai fixed it on LoongArch, but I found xtensa
> > obviously has the same issue.
> >
>
> Maybe I am doing something wrong, but this patch doesn't build
> for me.
>
>  CC      arch/xtensa/kernel/asm-offsets.s
> In file included from ./include/linux/highmem.h:8,
>                  from ./include/linux/bvec.h:10,
>                  from ./include/linux/blk_types.h:10,
>                  from ./include/linux/writeback.h:13,
>                  from ./include/linux/memcontrol.h:23,
>                  from ./include/linux/swap.h:9,
>                  from ./include/linux/suspend.h:5,
>                  from arch/xtensa/kernel/asm-offsets.c:24:
> ./include/linux/cacheflush.h:9:5: error: "ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE" is not defined, evaluates to 0 [-Werror=undef]
>     9 | #if ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE

is it because xtensa doesn't include this at the end of
arch/xtensa/include/asm/cacheflush.h
while other architectures do?

#include <asm-generic/cacheflush.h>



>
> Guenter

Re: [PATCH] xtensa: remove redundant flush_dcache_page and ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE macros

[Guenter Roeck]

On 3/17/24 17:27, Barry Song wrote:
> On Mon, Mar 18, 2024 at 8:16 AM Guenter Roeck <linux@roeck-us.net> wrote:
>>
>> On Wed, Mar 13, 2024 at 05:50:36PM +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' [-Wunused-variable]
>>>       174 |                         struct page *dst_page = sg_page(req->dst);
>>>           |
>>>
>>> The issue was originally reported on LoongArch by kernel test
>>> robot. And Huacai fixed it on LoongArch, but I found xtensa
>>> obviously has the same issue.
>>>
>>
>> Maybe I am doing something wrong, but this patch doesn't build
>> for me.
>>
>>   CC      arch/xtensa/kernel/asm-offsets.s
>> In file included from ./include/linux/highmem.h:8,
>>                   from ./include/linux/bvec.h:10,
>>                   from ./include/linux/blk_types.h:10,
>>                   from ./include/linux/writeback.h:13,
>>                   from ./include/linux/memcontrol.h:23,
>>                   from ./include/linux/swap.h:9,
>>                   from ./include/linux/suspend.h:5,
>>                   from arch/xtensa/kernel/asm-offsets.c:24:
>> ./include/linux/cacheflush.h:9:5: error: "ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE" is not defined, evaluates to 0 [-Werror=undef]
>>      9 | #if ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE
> 
> is it because xtensa doesn't include this at the end of
> arch/xtensa/include/asm/cacheflush.h
> while other architectures do?
> 
> #include <asm-generic/cacheflush.h>
> 

Looks like it (see my other e-mail).

Guenter

Re: [PATCH] xtensa: remove redundant flush_dcache_page and ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE macros

[Barry Song]

On Mon, Mar 18, 2024 at 8:34 AM Guenter Roeck <linux@roeck-us.net> wrote:
>
> On 3/17/24 17:27, Barry Song wrote:
> > On Mon, Mar 18, 2024 at 8:16 AM Guenter Roeck <linux@roeck-us.net> wrote:
> >>
> >> On Wed, Mar 13, 2024 at 05:50:36PM +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' [-Wunused-variable]
> >>>       174 |                         struct page *dst_page = sg_page(req->dst);
> >>>           |
> >>>
> >>> The issue was originally reported on LoongArch by kernel test
> >>> robot. And Huacai fixed it on LoongArch, but I found xtensa
> >>> obviously has the same issue.
> >>>
> >>
> >> Maybe I am doing something wrong, but this patch doesn't build
> >> for me.
> >>
> >>   CC      arch/xtensa/kernel/asm-offsets.s
> >> In file included from ./include/linux/highmem.h:8,
> >>                   from ./include/linux/bvec.h:10,
> >>                   from ./include/linux/blk_types.h:10,
> >>                   from ./include/linux/writeback.h:13,
> >>                   from ./include/linux/memcontrol.h:23,
> >>                   from ./include/linux/swap.h:9,
> >>                   from ./include/linux/suspend.h:5,
> >>                   from arch/xtensa/kernel/asm-offsets.c:24:
> >> ./include/linux/cacheflush.h:9:5: error: "ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE" is not defined, evaluates to 0 [-Werror=undef]
> >>      9 | #if ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE
> >
> > is it because xtensa doesn't include this at the end of
> > arch/xtensa/include/asm/cacheflush.h
> > while other architectures do?
> >
> > #include <asm-generic/cacheflush.h>
> >
>
> Looks like it (see my other e-mail).

i will send v2 and it seems a lot of other code can also be removed in
arch/xtensa/include/asm/cacheflush.h,

for example

#define flush_cache_all() do { } while (0)
#define flush_cache_mm(mm) do { } while (0)
#define flush_cache_dup_mm(mm) do { } while (0)

#define flush_cache_vmap(start,end) do { } while (0)
#define flush_cache_vmap_early(start,end) do { } while (0)
#define flush_cache_vunmap(start,end) do { } while (0)

#define ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE 0
#define flush_dcache_page(page) do { } while (0)

#define flush_cache_page(vma, addr, pfn) do { } while (0)
#define flush_cache_range(vma, start, end) do { } while (0)


#define flush_dcache_mmap_lock(mapping) do { } while (0)
#define flush_dcache_mmap_unlock(mapping) do { } while (0)

>
> Guenter
>