linux-kernel - Re: [PATCH v4 66/66] mm/mmap: Drop range_has

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Date:   Fri, 21 Jan 2022 10:51:38 +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 66/66] mm/mmap: Drop range_has_overlap() function

On 12/1/21 15:30, Liam Howlett wrote:
> From: "Liam R. Howlett" <Liam.Howlett@...cle.com>
> 
> Since there is no longer a linked list, the range_has_overlap() function
> is identical to the find_vma_intersection() function.  There is only one
> place that actually needs the previous vma, so just use vma_prev() in
> that one case.

I guess that was written before some further changes and now it's removing
just one user that doesn't care about pprev.

> Signed-off-by: Liam R. Howlett <Liam.Howlett@...cle.com>

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

> ---
>  mm/mmap.c | 28 +---------------------------
>  1 file changed, 1 insertion(+), 27 deletions(-)
> 
> diff --git a/mm/mmap.c b/mm/mmap.c
> index e13c6ef76697..4dfe2f92796e 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -420,30 +420,6 @@ anon_vma_interval_tree_post_update_vma(struct vm_area_struct *vma)
>  		anon_vma_interval_tree_insert(avc, &avc->anon_vma->rb_root);
>  }
>  
> -/*
> - * range_has_overlap() - Check the @start - @end range for overlapping VMAs and
> - * sets up a pointer to the previous VMA
> - * @mm: the mm struct
> - * @start: the start address of the range
> - * @end: the end address of the range
> - * @pprev: the pointer to the pointer of the previous VMA
> - *
> - * Returns: True if there is an overlapping VMA, false otherwise
> - */
> -static inline
> -bool range_has_overlap(struct mm_struct *mm, unsigned long start,
> -		       unsigned long end, struct vm_area_struct **pprev)
> -{
> -	struct vm_area_struct *existing;
> -
> -	MA_STATE(mas, &mm->mm_mt, start, start);
> -	rcu_read_lock();
> -	existing = mas_find(&mas, end - 1);
> -	*pprev = mas_prev(&mas, 0);
> -	rcu_read_unlock();
> -	return existing ? true : false;
> -}
> -
>  static unsigned long count_vma_pages_range(struct mm_struct *mm,
>  		unsigned long addr, unsigned long end)
>  {
> @@ -3188,9 +3164,7 @@ void exit_mmap(struct mm_struct *mm)
>   */
>  int insert_vm_struct(struct mm_struct *mm, struct vm_area_struct *vma)
>  {
> -	struct vm_area_struct *prev;
> -
> -	if (range_has_overlap(mm, vma->vm_start, vma->vm_end, &prev))
> +	if (find_vma_intersection(mm, vma->vm_start, vma->vm_end))
>  		return -ENOMEM;
>  
>  	if ((vma->vm_flags & VM_ACCOUNT) &&