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    Subject[PATCH v10 10/69] mmap: use the VMA iterator in count_vma_pages_range()
    Date
    From: "Matthew Wilcox (Oracle)" <willy@infradead.org>

    This simplifies the implementation and is faster than using the linked
    list.

    Link: https://lkml.kernel.org/r/20220504010716.661115-12-Liam.Howlett@oracle.com
    Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
    Signed-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
    Acked-by: Vlastimil Babka <vbabka@suse.cz>
    Cc: Catalin Marinas <catalin.marinas@arm.com>
    Cc: David Howells <dhowells@redhat.com>
    Cc: SeongJae Park <sj@kernel.org>
    Cc: Will Deacon <will@kernel.org>
    Cc: Davidlohr Bueso <dave@stgolabs.net>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
    ---
    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);

    - 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;
    --
    2.35.1
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