linux-kernel - Re: [PATCH v4 19/66] mm: Optimize find_exact_vma() to use vma

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Date:   Wed, 12 Jan 2022 17:31:06 +0100
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Liam Howlett <liam.howlett@...cle.com>,
        "maple-tree@...ts.infradead.org" <maple-tree@...ts.infradead.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     Song Liu <songliubraving@...com>,
        Davidlohr Bueso <dave@...olabs.net>,
        "Paul E . McKenney" <paulmck@...nel.org>,
        Matthew Wilcox <willy@...radead.org>,
        Laurent Dufour <ldufour@...ux.ibm.com>,
        David Rientjes <rientjes@...gle.com>,
        Axel Rasmussen <axelrasmussen@...gle.com>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Rik van Riel <riel@...riel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Michel Lespinasse <walken.cr@...il.com>,
        Jerome Glisse <jglisse@...hat.com>,
        Minchan Kim <minchan@...gle.com>,
        Joel Fernandes <joelaf@...gle.com>,
        Rom Lemarchand <romlem@...gle.com>
Subject: Re: [PATCH v4 19/66] mm: Optimize find_exact_vma() to use
 vma_lookup()

On 12/1/21 15:29, Liam Howlett wrote:
> From: "Liam R. Howlett" <Liam.Howlett@...cle.com>
> 
> Use vma_lookup() to walk the tree to the start value requested.  If
> the vma at the start does not match, then the answer is NULL and there
> is no need to look at the next vma the way that find_vma() would.
> 
> Signed-off-by: Liam R. Howlett <Liam.Howlett@...cle.com>

Reviewed-by: Vlastimil Babka <vbabka@...e.cz>

> ---
>  include/linux/mm.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 784f8fec3b65..c08f6d541b8a 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -2879,7 +2879,7 @@ static inline unsigned long vma_pages(struct vm_area_struct *vma)
>  static inline struct vm_area_struct *find_exact_vma(struct mm_struct *mm,
>  				unsigned long vm_start, unsigned long vm_end)
>  {
> -	struct vm_area_struct *vma = find_vma(mm, vm_start);
> +	struct vm_area_struct *vma = vma_lookup(mm, vm_start);
>  
>  	if (vma && (vma->vm_start != vm_start || vma->vm_end != vm_end))
>  		vma = NULL;