Subject: Re: [PATCH v3 1/5] powerpc/mm: Remove intermediate bitmap copy in 'slices'

From: "Aneesh Kumar K.V" <[email-masked]>
Date: Mon, 29 Jan 2018 11:47:54 +0530

Christophe Leroy <[email-masked]> writes:

> bitmap_or() and bitmap_andnot() can work properly with dst identical
> to src1 or src2. There is no need of an intermediate result bitmap
> that is copied back to dst in a second step.
>
Reviewed-by: Aneesh Kumar K.V <[email-masked]>
> Signed-off-by: Christophe Leroy <[email-masked]>
> ---
>  v2: New in v2
>  v3: patch moved up front of the serie to avoid ephemeral slice_bitmap_copy() function in following patch
>
>  arch/powerpc/mm/slice.c | 12 ++++--------
>  1 file changed, 4 insertions(+), 8 deletions(-)
>
> diff --git a/arch/powerpc/mm/slice.c b/arch/powerpc/mm/slice.c
> index 23ec2c5e3b78..98b53d48968f 100644
> --- a/arch/powerpc/mm/slice.c
> +++ b/arch/powerpc/mm/slice.c
> @@ -388,21 +388,17 @@ static unsigned long slice_find_area(struct mm_struct *mm, unsigned long len,
>  
>  static inline void slice_or_mask(struct slice_mask *dst, struct slice_mask *src)
>  {
> -	DECLARE_BITMAP(result, SLICE_NUM_HIGH);
> -
>  	dst->low_slices |= src->low_slices;
> -	bitmap_or(result, dst->high_slices, src->high_slices, SLICE_NUM_HIGH);
> -	bitmap_copy(dst->high_slices, result, SLICE_NUM_HIGH);
> +	bitmap_or(dst->high_slices, dst->high_slices, src->high_slices,
> +		  SLICE_NUM_HIGH);
>  }
>  
>  static inline void slice_andnot_mask(struct slice_mask *dst, struct slice_mask *src)
>  {
> -	DECLARE_BITMAP(result, SLICE_NUM_HIGH);
> -
>  	dst->low_slices &= ~src->low_slices;
>  
> -	bitmap_andnot(result, dst->high_slices, src->high_slices, SLICE_NUM_HIGH);
> -	bitmap_copy(dst->high_slices, result, SLICE_NUM_HIGH);
> +	bitmap_andnot(dst->high_slices, dst->high_slices, src->high_slices,
> +		      SLICE_NUM_HIGH);
>  }
>  
>  #ifdef CONFIG_PPC_64K_PAGES
> -- 
> 2.13.3