linux-kernel - Re: [PATCH v4 15/66] mm: Convert vma

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Date:   Fri, 17 Dec 2021 12:59:01 +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 15/66] mm: Convert vma_lookup() to use the Maple Tree

Re: subject. It already uses the Maple Tree via find_vma(). So more accurate
would be e.g. "to use mtree_load()"?

Note there's also the side-effect of not using vmacache anymore (which is
still used in find_vma()), thus again potentially biasing results of later
vmacache removal. But seems like vma_lookup() is not used from hotpaths, so
it should be fine.

On 12/1/21 15:29, Liam Howlett wrote:
> From: "Matthew Wilcox (Oracle)" <willy@...radead.org>
> 
> Unlike the rbtree, the Maple Tree will return a NULL if there's
> nothing at a particular address.
> 
> Signed-off-by: Matthew Wilcox (Oracle) <willy@...radead.org>
> Signed-off-by: Liam R. Howlett <Liam.Howlett@...cle.com>

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

> ---
>  include/linux/mm.h | 7 +------
>  1 file changed, 1 insertion(+), 6 deletions(-)
> 
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 4d5ab70b1f6d..c28bd97a4ecd 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -2845,12 +2845,7 @@ struct vm_area_struct *find_vma_intersection(struct mm_struct *mm,
>  static inline
>  struct vm_area_struct *vma_lookup(struct mm_struct *mm, unsigned long addr)
>  {
> -	struct vm_area_struct *vma = find_vma(mm, addr);
> -
> -	if (vma && addr < vma->vm_start)
> -		vma = NULL;
> -
> -	return vma;
> +	return mtree_load(&mm->mm_mt, addr);
>  }
>  
>  static inline unsigned long vm_start_gap(struct vm_area_struct *vma)