linux-kernel - Re: [PATCH v2] mm: madvise: use walk_page_range_vma() instead of walk_page

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Message-ID: <aEFf5Xw9V79j0W88@harry>
Date: Thu, 5 Jun 2025 18:14:13 +0900
From: Harry Yoo <harry.yoo@...cle.com>
To: Barry Song <21cnbao@...il.com>
Cc: linux-mm@...ck.org, akpm@...ux-foundation.org,
        linux-kernel@...r.kernel.org, Barry Song <v-songbaohua@...o.com>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
        David Hildenbrand <david@...hat.com>,
        Oscar Salvador <osalvador@...e.de>,
        "Liam R. Howlett" <Liam.Howlett@...cle.com>,
        Vlastimil Babka <vbabka@...e.cz>, Jann Horn <jannh@...gle.com>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Lokesh Gidra <lokeshgidra@...gle.com>, Dev Jain <dev.jain@....com>,
        Tangquan Zheng <zhengtangquan@...o.com>
Subject: Re: [PATCH v2] mm: madvise: use walk_page_range_vma() instead of
 walk_page_range()

On Thu, Jun 05, 2025 at 08:31:44PM +1200, Barry Song wrote:
> From: Barry Song <v-songbaohua@...o.com>
> 
> We've already found the VMA within madvise_walk_vmas() before calling
> specific madvise behavior functions like madvise_free_single_vma().
> So calling walk_page_range() and doing find_vma() again seems
> unnecessary. It also prevents potential optimizations in those madvise
> callbacks, particularly the use of dedicated per-VMA locking.
> 
> Reviewed-by: Anshuman Khandual <anshuman.khandual@....com>
> Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
> Acked-by: David Hildenbrand <david@...hat.com>
> Reviewed-by: Oscar Salvador <osalvador@...e.de>
> Cc: "Liam R. Howlett" <Liam.Howlett@...cle.com>
> Cc: Vlastimil Babka <vbabka@...e.cz>
> Cc: Jann Horn <jannh@...gle.com>
> Cc: Suren Baghdasaryan <surenb@...gle.com>
> Cc: Lokesh Gidra <lokeshgidra@...gle.com>
> Cc: Dev Jain <dev.jain@....com>
> Cc: Tangquan Zheng <zhengtangquan@...o.com>
> Signed-off-by: Barry Song <v-songbaohua@...o.com>

Nice!

Looks good to me,
Reviewed-by: Harry Yoo <harry.yoo@...cle.com>

-- 
Cheers,
Harry / Hyeonggon

> ---
>  -v2:
>   * Also extend the modification to callbacks beyond
>     madvise_free_single_vma() since the code flow is
>     the same - Dev, Lorenzo
>  -rfc:
>   https://lore.kernel.org/linux-mm/20250603013154.5905-1-21cnbao@gmail.com/
> 
>  mm/madvise.c | 12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/mm/madvise.c b/mm/madvise.c
> index 5f7a66a1617e..56d9ca2557b9 100644
> --- a/mm/madvise.c
> +++ b/mm/madvise.c
> @@ -282,7 +282,7 @@ static long madvise_willneed(struct vm_area_struct *vma,
>  	*prev = vma;
>  #ifdef CONFIG_SWAP
>  	if (!file) {
> -		walk_page_range(vma->vm_mm, start, end, &swapin_walk_ops, vma);
> +		walk_page_range_vma(vma, start, end, &swapin_walk_ops, vma);
>  		lru_add_drain(); /* Push any new pages onto the LRU now */
>  		return 0;
>  	}
> @@ -581,7 +581,7 @@ static void madvise_cold_page_range(struct mmu_gather *tlb,
>  	};
>  
>  	tlb_start_vma(tlb, vma);
> -	walk_page_range(vma->vm_mm, addr, end, &cold_walk_ops, &walk_private);
> +	walk_page_range_vma(vma, addr, end, &cold_walk_ops, &walk_private);
>  	tlb_end_vma(tlb, vma);
>  }
>  
> @@ -619,7 +619,7 @@ static void madvise_pageout_page_range(struct mmu_gather *tlb,
>  	};
>  
>  	tlb_start_vma(tlb, vma);
> -	walk_page_range(vma->vm_mm, addr, end, &cold_walk_ops, &walk_private);
> +	walk_page_range_vma(vma, addr, end, &cold_walk_ops, &walk_private);
>  	tlb_end_vma(tlb, vma);
>  }
>  
> @@ -825,7 +825,7 @@ static int madvise_free_single_vma(struct madvise_behavior *madv_behavior,
>  
>  	mmu_notifier_invalidate_range_start(&range);
>  	tlb_start_vma(tlb, vma);
> -	walk_page_range(vma->vm_mm, range.start, range.end,
> +	walk_page_range_vma(vma, range.start, range.end,
>  			&madvise_free_walk_ops, tlb);
>  	tlb_end_vma(tlb, vma);
>  	mmu_notifier_invalidate_range_end(&range);
> @@ -1160,7 +1160,7 @@ static long madvise_guard_install(struct vm_area_struct *vma,
>  		unsigned long nr_pages = 0;
>  
>  		/* Returns < 0 on error, == 0 if success, > 0 if zap needed. */
> -		err = walk_page_range_mm(vma->vm_mm, start, end,
> +		err = walk_page_range_vma(vma, start, end,
>  					 &guard_install_walk_ops, &nr_pages);
>  		if (err < 0)
>  			return err;
> @@ -1244,7 +1244,7 @@ static long madvise_guard_remove(struct vm_area_struct *vma,
>  	if (!is_valid_guard_vma(vma, /* allow_locked = */true))
>  		return -EINVAL;
>  
> -	return walk_page_range(vma->vm_mm, start, end,
> +	return walk_page_range_vma(vma, start, end,
>  			       &guard_remove_walk_ops, NULL);
>  }
>  
> -- 
> 2.39.3 (Apple Git-146)
> 
>