Re: [PATCH v10 10/69] mmap: use the VMA iterator in count_vma_pages_range()

[Liam Howlett]

* David Hildenbrand <david@xxxxxxxxxx> [220621 17:13]:
> On 21.06.22 22:46, Liam Howlett wrote:
> > From: "Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx>
> > 
> > This simplifies the implementation and is faster than using the linked
> > list.
> > 
> > Link: https://lkml.kernel.org/r/20220504010716.661115-12-Liam.Howlett@xxxxxxxxxx
> > Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
> > Signed-off-by: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx>
> > Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
> > Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
> > Cc: David Howells <dhowells@xxxxxxxxxx>
> > Cc: SeongJae Park <sj@xxxxxxxxxx>
> > Cc: Will Deacon <will@xxxxxxxxxx>
> > Cc: Davidlohr Bueso <dave@xxxxxxxxxxxx>
> > Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> > ---
> >  mm/mmap.c | 24 +++++++-----------------
> >  1 file changed, 7 insertions(+), 17 deletions(-)
> > 
> > diff --git a/mm/mmap.c b/mm/mmap.c
> > index 6be7833c781b..d7e6baa2f40f 100644
> > --- a/mm/mmap.c
> > +++ b/mm/mmap.c
> > @@ -675,29 +675,19 @@ munmap_vma_range(struct mm_struct *mm, unsigned long start, unsigned long len,
> >  
> >  	return 0;
> >  }
> > +
> >  static unsigned long count_vma_pages_range(struct mm_struct *mm,
> >  		unsigned long addr, unsigned long end)
> >  {
> > -	unsigned long nr_pages = 0;
> > +	VMA_ITERATOR(vmi, mm, addr);
> >  	struct vm_area_struct *vma;
> > +	unsigned long nr_pages = 0;
> >  
> > -	/* Find first overlapping mapping */
> > -	vma = find_vma_intersection(mm, addr, end);
> > -	if (!vma)
> > -		return 0;
> > -
> > -	nr_pages = (min(end, vma->vm_end) -
> > -		max(addr, vma->vm_start)) >> PAGE_SHIFT;
> > -
> > -	/* Iterate over the rest of the overlaps */
> > -	for (vma = vma->vm_next; vma; vma = vma->vm_next) {
> > -		unsigned long overlap_len;
> > -
> > -		if (vma->vm_start > end)
> > -			break;
> > +	for_each_vma_range(vmi, vma, end) {
> > +		unsigned long vm_start = max(addr, vma->vm_start);
> > +		unsigned long vm_end = min(end, vma->vm_end);
> 
> I thought using max_t and min_t was the latest advisory. I might be
> wrong and simply kept doing it that way ;)

They are the same type so I think this is okay.

> 
> >  
> > -		overlap_len = min(end, vma->vm_end) - vma->vm_start;
> > -		nr_pages += overlap_len >> PAGE_SHIFT;
> > +		nr_pages += (vm_end - vm_start) / PAGE_SIZE;
> 
> PHYS_PFN(vm_end - vm_start)
> 
> >  	}
> >  
> >  	return nr_pages;
> 
> Reviewed-by: David Hildenbrand <david@xxxxxxxxxx>
> 
> -- 
> Thanks,
> 
> David / dhildenb
>