linux-kernel - Re: [PATCH 3/5] swap: fold swap_ra_clamp_pfn into swap_ra

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Message-ID: <87r0x9qmys.fsf@yhuang6-desk2.ccr.corp.intel.com>
Date:   Fri, 09 Dec 2022 11:23:39 +0800
From:   "Huang, Ying" <ying.huang@...el.com>
To:     Kairui Song <ryncsn@...il.com>
Cc:     linux-mm@...ck.org, Kairui Song <kasong@...cent.com>,
        linux-kernel@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Miaohe Lin <linmiaohe@...wei.com>,
        David Hildenbrand <david@...hat.com>,
        Hugh Dickins <hughd@...gle.com>
Subject: Re: [PATCH 3/5] swap: fold swap_ra_clamp_pfn into swap_ra_info

Kairui Song <ryncsn@...il.com> writes:

> From: Kairui Song <kasong@...cent.com>
>
> This make the code cleaner. This helper is made of only two line of
> self explanational code and not reused anywhere else.
>
> And this actually make the compiled object smaller by a bit:
>
>           text    data     bss     dec     hex filename
> Before:   9502     976      12   10490    28fa mm/swap_state.o
> After:    9470     976      12   10458    28da mm/swap_state.o
>
> Signed-off-by: Kairui Song <kasong@...cent.com>
> ---
>  mm/swap_state.c | 44 +++++++++++++++++++-------------------------
>  1 file changed, 19 insertions(+), 25 deletions(-)

LGTM, Thanks!

Reviewed-by: "Huang, Ying" <ying.huang@...el.com>

> diff --git a/mm/swap_state.c b/mm/swap_state.c
> index 60136bda78e3..19089417abd1 100644
> --- a/mm/swap_state.c
> +++ b/mm/swap_state.c
> @@ -696,28 +696,15 @@ void exit_swap_address_space(unsigned int type)
>  	swapper_spaces[type] = NULL;
>  }
>  
> -static inline void swap_ra_clamp_pfn(struct vm_area_struct *vma,
> -				     unsigned long faddr,
> -				     unsigned long lpfn,
> -				     unsigned long rpfn,
> -				     unsigned long *start,
> -				     unsigned long *end)
> -{
> -	*start = max3(lpfn, PFN_DOWN(vma->vm_start),
> -		      PFN_DOWN(faddr & PMD_MASK));
> -	*end = min3(rpfn, PFN_DOWN(vma->vm_end),
> -		    PFN_DOWN((faddr & PMD_MASK) + PMD_SIZE));
> -}
> -
>  static void swap_ra_info(struct vm_fault *vmf,
> -			struct vma_swap_readahead *ra_info)
> +			 struct vma_swap_readahead *ra_info)
>  {
>  	struct vm_area_struct *vma = vmf->vma;
>  	unsigned long ra_val;
> -	unsigned long faddr, pfn, fpfn;
> +	unsigned long faddr, pfn, fpfn, lpfn, rpfn;
>  	unsigned long start, end;
>  	pte_t *pte, *orig_pte;
> -	unsigned int max_win, hits, prev_win, win, left;
> +	unsigned int max_win, hits, prev_win, win;
>  #ifndef CONFIG_64BIT
>  	pte_t *tpte;
>  #endif
> @@ -745,16 +732,23 @@ static void swap_ra_info(struct vm_fault *vmf,
>  
>  	/* Copy the PTEs because the page table may be unmapped */
>  	orig_pte = pte = pte_offset_map(vmf->pmd, faddr);
> -	if (fpfn == pfn + 1)
> -		swap_ra_clamp_pfn(vma, faddr, fpfn, fpfn + win, &start, &end);
> -	else if (pfn == fpfn + 1)
> -		swap_ra_clamp_pfn(vma, faddr, fpfn - win + 1, fpfn + 1,
> -				  &start, &end);
> -	else {
> -		left = (win - 1) / 2;
> -		swap_ra_clamp_pfn(vma, faddr, fpfn - left, fpfn + win - left,
> -				  &start, &end);
> +	if (fpfn == pfn + 1) {
> +		lpfn = fpfn;
> +		rpfn = fpfn + win;
> +	} else if (pfn == fpfn + 1) {
> +		lpfn = fpfn - win + 1;
> +		rpfn = fpfn + 1;
> +	} else {
> +		unsigned int left = (win - 1) / 2;
> +
> +		lpfn = fpfn - left;
> +		rpfn = fpfn + win - left;
>  	}
> +	start = max3(lpfn, PFN_DOWN(vma->vm_start),
> +		     PFN_DOWN(faddr & PMD_MASK));
> +	end = min3(rpfn, PFN_DOWN(vma->vm_end),
> +		   PFN_DOWN((faddr & PMD_MASK) + PMD_SIZE));
> +
>  	ra_info->nr_pte = end - start;
>  	ra_info->offset = fpfn - start;
>  	pte -= ra_info->offset;