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

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Date:   Mon, 12 Sep 2022 14:01:28 -0600
From:   Yu Zhao <yuzhao@...gle.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
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, Sep 12, 2022 at 12:45:59PM -0700, Andrew Morton wrote:
> 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?

The above replaces the original patch in mm-unstable.

> It's almost what is in mm-unstable/linux-next
> at present?

Yes, almost.

> 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.

The diff between the original patch and this one, in case you prefer to
fix it atop rather than amend.

diff --git a/mm/vmscan.c b/mm/vmscan.c
index a7c5d15c1618..cadcc3290918 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -3776,7 +3776,10 @@ static bool get_next_vma(unsigned long mask, unsigned long size, struct mm_walk
 	VM_WARN_ON_ONCE(mask & size);
 	VM_WARN_ON_ONCE((start & mask) != (*vm_start & mask));
 
-	for_each_vma_range(vmi, args->vma, end) {
+	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))
 			continue;