linux-kernel - Re: [PATCH v14 67/70] mm/vmscan: Use vma iterator instead of vm

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Date:   Mon, 12 Sep 2022 12:45:59 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Yu Zhao <yuzhao@...gle.com>
Cc:     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>
Subject: Re: [PATCH v14 67/70] mm/vmscan: Use vma iterator instead of
 vm_next

On Mon, 12 Sep 2022 00:55:08 -0600 Yu Zhao <yuzhao@...gle.com> wrote:

> 
> The following should work properly. Please take a look. Thanks!
> 
> ---
>  mm/vmscan.c | 12 +++---------
>  1 file changed, 3 insertions(+), 9 deletions(-)
> 
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 11a86d47e85e..b22d3efe3031 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -3776,23 +3776,17 @@ static bool get_next_vma(unsigned long mask, unsigned long size, struct mm_walk
>  {
>  	unsigned long start = round_up(*vm_end, size);
>  	unsigned long end = (start | ~mask) + 1;
> +	VMA_ITERATOR(vmi, args->mm, start);
>  
>  	VM_WARN_ON_ONCE(mask & size);
>  	VM_WARN_ON_ONCE((start & mask) != (*vm_start & mask));
>  
> -	while (args->vma) {
> -		if (start >= args->vma->vm_end) {
> -			args->vma = args->vma->vm_next;
> -			continue;
> -		}
> -
> +	for_each_vma(vmi, args->vma) {
>  		if (end && end <= args->vma->vm_start)
>  			return false;
>  
> -		if (should_skip_vma(args->vma->vm_start, args->vma->vm_end, args)) {
> -			args->vma = args->vma->vm_next;
> +		if (should_skip_vma(args->vma->vm_start, args->vma->vm_end, args))
>  			continue;
> -		}
>  
>  		*vm_start = max(start, args->vma->vm_start);
>  		*vm_end = min(end - 1, args->vma->vm_end - 1) + 1;

What does this apply to?  It's almost what is in mm-unstable/linux-next
at present?

static bool get_next_vma(unsigned long mask, unsigned long size, struct mm_walk *args,
			 unsigned long *vm_start, unsigned long *vm_end)
{
	unsigned long start = round_up(*vm_end, size);
	unsigned long end = (start | ~mask) + 1;
	VMA_ITERATOR(vmi, args->mm, start);

	VM_WARN_ON_ONCE(mask & size);
	VM_WARN_ON_ONCE((start & mask) != (*vm_start & mask));

	for_each_vma_range(vmi, args->vma, end) {
		if (should_skip_vma(args->vma->vm_start, args->vma->vm_end, args))
			continue;

		*vm_start = max(start, args->vma->vm_start);
		*vm_end = min(end - 1, args->vma->vm_end - 1) + 1;

		return true;
	}

	return false;
}

for_each_vma_range versus for_each_vma.