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    SubjectRe: [PATCH v4 10/66] mm/mmap: Use the maple tree for find_vma_prev() instead of the rbtree
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    On 12/1/21 15:29, Liam Howlett wrote:
    > From: "Liam R. Howlett" <Liam.Howlett@Oracle.com>
    >
    > Use the maple tree's advanced API and a maple state to walk the tree
    > for the entry at the address of the next vma, then use the maple state
    > to walk back one entry to find the previous entry.
    >
    > Add kernel documentation comments for this API.
    >
    > Signed-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
    > Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

    Acked-by: Vlastimil Babka <vbabka@suse.cz>

    > ---
    > mm/mmap.c | 24 ++++++++++++++----------
    > 1 file changed, 14 insertions(+), 10 deletions(-)
    >
    > diff --git a/mm/mmap.c b/mm/mmap.c
    > index 6a7502f74190..8425ab573770 100644
    > --- a/mm/mmap.c
    > +++ b/mm/mmap.c
    > @@ -2454,23 +2454,27 @@ struct vm_area_struct *find_vma(struct mm_struct *mm, unsigned long addr)
    > }
    > EXPORT_SYMBOL(find_vma);
    >
    > -/*
    > - * Same as find_vma, but also return a pointer to the previous VMA in *pprev.
    > +/**
    > + * find_vma_prev() - Find the VMA for a given address, or the next vma and
    > + * set %pprev to the previous VMA, if any.
    > + * @mm: The mm_struct to check
    > + * @addr: The address
    > + * @pprev: The pointer to set to the previous VMA
    > + *
    > + * Returns: The VMA associated with @addr, or the next vma.
    > + * May return %NULL in the case of no vma at addr or above.
    > */
    > struct vm_area_struct *
    > find_vma_prev(struct mm_struct *mm, unsigned long addr,
    > struct vm_area_struct **pprev)
    > {
    > struct vm_area_struct *vma;
    > + MA_STATE(mas, &mm->mm_mt, addr, addr);
    >
    > - vma = find_vma(mm, addr);
    > - if (vma) {
    > - *pprev = vma->vm_prev;
    > - } else {
    > - struct rb_node *rb_node = rb_last(&mm->mm_rb);
    > -
    > - *pprev = rb_node ? rb_entry(rb_node, struct vm_area_struct, vm_rb) : NULL;
    > - }
    > + vma = mas_walk(&mas);
    > + *pprev = mas_prev(&mas, 0);
    > + if (!vma)
    > + vma = mas_next(&mas, ULONG_MAX);
    > return vma;
    > }
    >

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