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    SubjectRe: [PATCH v4 08/66] mmap: Use the VMA iterator in count_vma_pages_range()
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    * Vlastimil Babka <vbabka@suse.cz> [211209 10:54]:
    > On 12/1/21 15:29, Liam Howlett wrote:
    > > From: "Matthew Wilcox (Oracle)" <willy@infradead.org>
    > >
    > > This simplifies the implementation and is faster than using the linked
    > > list.
    >
    > You mean faster because more cache friendly?
    > OTOH you do max(addr, vma->vm_start) which wasn't the case.
    >
    > I doubt it matters though and yeah it's much simpler...
    >
    > > Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
    > Acked-by: Vlastimil Babka <vbabka@suse.cz>
    >
    > Btw, no signed-off-by Liam?
    >
    > I now also notice some other patches (e.g. patch 4) have From: and s-o-b by
    > Liam followed by Matthew, despite it's Liam sending them. I guess that's
    > less of an issue than the missing one.
    >
    > Anyway something for you to check and make consistent in the whole series, I
    > won't point it out individually.

    Thanks for catching this. I will clean up the s-o-b for the next
    revision.

    >
    > > ---
    > > mm/mmap.c | 24 +++++++-----------------
    > > 1 file changed, 7 insertions(+), 17 deletions(-)
    > >
    > > diff --git a/mm/mmap.c b/mm/mmap.c
    > > index 9fee6e6b276f..de78fc0ce809 100644
    > > --- a/mm/mmap.c
    > > +++ b/mm/mmap.c
    > > @@ -669,29 +669,19 @@ 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);
    > >
    > > - overlap_len = min(end, vma->vm_end) - vma->vm_start;
    > > - nr_pages += overlap_len >> PAGE_SHIFT;
    > > + nr_pages += (vm_end - vm_start) / PAGE_SIZE;
    > > }
    > >
    > > return nr_pages;
    >
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