linux-kernel - Re: [PATCH v2 1/2] mm: Make pte_range_none() return number of empty PTEs

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Message-ID: <3f15a44d-cf49-41f4-892b-cb3202603652@linux.alibaba.com>
Date: Wed, 18 Sep 2024 15:03:01 +0800
From: Baolin Wang <baolin.wang@...ux.alibaba.com>
To: Dev Jain <dev.jain@....com>, akpm@...ux-foundation.org, david@...hat.com,
 willy@...radead.org
Cc: ryan.roberts@....com, anshuman.khandual@....com, baohua@...nel.org,
 hughd@...gle.com, ioworker0@...il.com, wangkefeng.wang@...wei.com,
 gshan@...hat.com, linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH v2 1/2] mm: Make pte_range_none() return number of empty
 PTEs



On 2024/9/16 19:07, Dev Jain wrote:
> In preparation for the second patch, make pte_range_none() return
> the number of contiguous empty PTEs.
> 
> Signed-off-by: Dev Jain <dev.jain@....com>

LGTM.
Reviewed-by: Baolin Wang <baolin.wang@...ux.alibaba.com>

> ---
>   mm/memory.c | 12 ++++++------
>   1 file changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/mm/memory.c b/mm/memory.c
> index 6469ac99f2f7..8bb1236de93c 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -4617,16 +4617,16 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
>   	return ret;
>   }
>   
> -static bool pte_range_none(pte_t *pte, int nr_pages)
> +static int pte_range_none(pte_t *pte, int nr_pages)
>   {
>   	int i;
>   
>   	for (i = 0; i < nr_pages; i++) {
>   		if (!pte_none(ptep_get_lockless(pte + i)))
> -			return false;
> +			return i;
>   	}
>   
> -	return true;
> +	return nr_pages;
>   }
>   
>   static struct folio *alloc_anon_folio(struct vm_fault *vmf)
> @@ -4671,7 +4671,7 @@ static struct folio *alloc_anon_folio(struct vm_fault *vmf)
>   	order = highest_order(orders);
>   	while (orders) {
>   		addr = ALIGN_DOWN(vmf->address, PAGE_SIZE << order);
> -		if (pte_range_none(pte + pte_index(addr), 1 << order))
> +		if (pte_range_none(pte + pte_index(addr), 1 << order) == 1 << order)
>   			break;
>   		order = next_order(&orders, order);
>   	}
> @@ -4787,7 +4787,7 @@ static vm_fault_t do_anonymous_page(struct vm_fault *vmf)
>   	if (nr_pages == 1 && vmf_pte_changed(vmf)) {
>   		update_mmu_tlb(vma, addr, vmf->pte);
>   		goto release;
> -	} else if (nr_pages > 1 && !pte_range_none(vmf->pte, nr_pages)) {
> +	} else if (nr_pages > 1 && pte_range_none(vmf->pte, nr_pages) != nr_pages) {
>   		update_mmu_tlb_range(vma, addr, vmf->pte, nr_pages);
>   		goto release;
>   	}
> @@ -5121,7 +5121,7 @@ vm_fault_t finish_fault(struct vm_fault *vmf)
>   		update_mmu_tlb(vma, addr, vmf->pte);
>   		ret = VM_FAULT_NOPAGE;
>   		goto unlock;
> -	} else if (nr_pages > 1 && !pte_range_none(vmf->pte, nr_pages)) {
> +	} else if (nr_pages > 1 && pte_range_none(vmf->pte, nr_pages) != nr_pages) {
>   		update_mmu_tlb_range(vma, addr, vmf->pte, nr_pages);
>   		ret = VM_FAULT_NOPAGE;
>   		goto unlock;