linux-kernel - Re: [PATCH v4 40/66] exec: Use VMA iterator instead of linked list

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Date:   Wed, 19 Jan 2022 12:06:59 +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 40/66] exec: Use VMA iterator instead of linked list

On 12/1/21 15:30, Liam Howlett wrote:
> From: "Liam R. Howlett" <Liam.Howlett@...cle.com>
> 
> Remove a use of the vm_next list by doing the initial lookup with the
> VMA iterator and then using it to find the next entry.
> 
> 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>

> ---
>  fs/exec.c | 9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/exec.c b/fs/exec.c
> index fee18b63ed35..f033745c148a 100644
> --- a/fs/exec.c
> +++ b/fs/exec.c
> @@ -680,6 +680,8 @@ static int shift_arg_pages(struct vm_area_struct *vma, unsigned long shift)
>  	unsigned long length = old_end - old_start;
>  	unsigned long new_start = old_start - shift;
>  	unsigned long new_end = old_end - shift;
> +	VMA_ITERATOR(vmi, mm, new_start);
> +	struct vm_area_struct *next;
>  	struct mmu_gather tlb;
>  
>  	BUG_ON(new_start > new_end);
> @@ -688,7 +690,7 @@ static int shift_arg_pages(struct vm_area_struct *vma, unsigned long shift)
>  	 * ensure there are no vmas between where we want to go
>  	 * and where we are
>  	 */
> -	if (vma != find_vma(mm, new_start))
> +	if (vma != vma_next(&vmi))
>  		return -EFAULT;
>  
>  	/*
> @@ -707,12 +709,13 @@ static int shift_arg_pages(struct vm_area_struct *vma, unsigned long shift)
>  
>  	lru_add_drain();
>  	tlb_gather_mmu(&tlb, mm);
> +	next = vma_next(&vmi);
>  	if (new_end > old_start) {
>  		/*
>  		 * when the old and new regions overlap clear from new_end.
>  		 */
>  		free_pgd_range(&tlb, new_end, old_end, new_end,
> -			vma->vm_next ? vma->vm_next->vm_start : USER_PGTABLES_CEILING);
> +			next ? next->vm_start : USER_PGTABLES_CEILING);
>  	} else {
>  		/*
>  		 * otherwise, clean from old_start; this is done to not touch
> @@ -721,7 +724,7 @@ static int shift_arg_pages(struct vm_area_struct *vma, unsigned long shift)
>  		 * for the others its just a little faster.
>  		 */
>  		free_pgd_range(&tlb, old_start, old_end, new_end,
> -			vma->vm_next ? vma->vm_next->vm_start : USER_PGTABLES_CEILING);
> +			next ? next->vm_start : USER_PGTABLES_CEILING);
>  	}
>  	tlb_finish_mmu(&tlb);
>