linux-kernel - Re: [PATCH 9/9] mm/madvise: remove !tlb support from madvise_{dontneed,free}_single

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Message-ID: <246b547e-d7ad-44c7-9652-6f5a72828b26@lucifer.local>
Date: Tue, 11 Mar 2025 14:01:20 +0000
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: SeongJae Park <sj@...nel.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
        "Liam R. Howlett" <howlett@...il.com>,
        David Hildenbrand <david@...hat.com>,
        Shakeel Butt <shakeel.butt@...ux.dev>,
        Vlastimil Babka <vbabka@...e.cz>, kernel-team@...a.com,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH 9/9] mm/madvise: remove !tlb support from
 madvise_{dontneed,free}_single_vma()

On Mon, Mar 10, 2025 at 10:23:18AM -0700, SeongJae Park wrote:
> madvise_dontneed_single_vma() and madvise_free_single_vma() support both
> batched tlb flushes and unbatched tlb flushes use cases depending on
> received tlb parameter's value.  The supports were for safe and fine
> transition of the usages from the unbatched flushes to the batched ones.
> Now the transition is done, and therefore there is no real unbatched tlb
> flushes use case.  Remove the code for supporting the no more being used
> cases.
>
> Signed-off-by: SeongJae Park <sj@...nel.org>

Obviously I support this based on previous preview :) but I wonder if we
can avoid this horrid caller_tlb pattern in the first instance.

FWIW:

Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>

> ---
>  mm/madvise.c | 19 ++-----------------
>  1 file changed, 2 insertions(+), 17 deletions(-)
>
> diff --git a/mm/madvise.c b/mm/madvise.c
> index d5f4ce3041a4..25af0a24c00b 100644
> --- a/mm/madvise.c
> +++ b/mm/madvise.c
> @@ -795,18 +795,11 @@ static const struct mm_walk_ops madvise_free_walk_ops = {
>  };
>
>  static int madvise_free_single_vma(
> -		struct mmu_gather *caller_tlb, struct vm_area_struct *vma,
> +		struct mmu_gather *tlb, struct vm_area_struct *vma,
>  		unsigned long start_addr, unsigned long end_addr)
>  {
>  	struct mm_struct *mm = vma->vm_mm;
>  	struct mmu_notifier_range range;
> -	struct mmu_gather self_tlb;
> -	struct mmu_gather *tlb;
> -
> -	if (caller_tlb)
> -		tlb = caller_tlb;
> -	else
> -		tlb = &self_tlb;
>
>  	/* MADV_FREE works for only anon vma at the moment */
>  	if (!vma_is_anonymous(vma))
> @@ -822,8 +815,6 @@ static int madvise_free_single_vma(
>  				range.start, range.end);
>
>  	lru_add_drain();
> -	if (!caller_tlb)
> -		tlb_gather_mmu(tlb, mm);
>  	update_hiwater_rss(mm);
>
>  	mmu_notifier_invalidate_range_start(&range);
> @@ -832,9 +823,6 @@ static int madvise_free_single_vma(
>  			&madvise_free_walk_ops, tlb);
>  	tlb_end_vma(tlb, vma);
>  	mmu_notifier_invalidate_range_end(&range);
> -	if (!caller_tlb)
> -		tlb_finish_mmu(tlb);
> -
>  	return 0;
>  }
>
> @@ -866,10 +854,7 @@ static long madvise_dontneed_single_vma(struct mmu_gather *tlb,
>  		.even_cows = true,
>  	};
>
> -	if (!tlb)
> -		zap_page_range_single(vma, start, end - start, &details);
> -	else
> -		unmap_vma_single(tlb, vma, start, end - start, &details);
> +	unmap_vma_single(tlb, vma, start, end - start, &details);
>  	return 0;
>  }
>
> --
> 2.39.5