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    Subject[PATCH 01/94] mm: Add vma_lookup()
    Date
    Many places in the kernel use find_vma() to get a vma and then check the
    start address of the vma to ensure the next vma was not returned.

    Other places use the find_vma_intersection() call with add, addr + 1 as
    the range; looking for just the vma at a specific address.

    The third use of find_vma() is by developers who do not know that the
    function starts searching at the provided address upwards for the next
    vma. This results in a bug that is often overlooked for a long time.

    Adding the new vma_lookup() function will allow for cleaner code by
    removing the find_vma() calls which check limits, making
    find_vma_intersection() calls of a single address to be shorter, and
    potentially reduce the incorrect uses of find_vma().

    Signed-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
    ---
    include/linux/mm.h | 13 +++++++++++++
    1 file changed, 13 insertions(+)

    diff --git a/include/linux/mm.h b/include/linux/mm.h
    index 25b9041f9925..7f7dff6ad884 100644
    --- a/include/linux/mm.h
    +++ b/include/linux/mm.h
    @@ -2689,6 +2689,19 @@ static inline struct vm_area_struct * find_vma_intersection(struct mm_struct * m
    return vma;
    }

    +/**
    + * vma_lookup() - Find a VMA at a specific address
    + * @mm: The process address space.
    + * @addr: The user address.
    + *
    + * Return: The vm_area_struct at the given address, %NULL otherwise.
    + */
    +static inline
    +struct vm_area_struct *vma_lookup(struct mm_struct *mm, unsigned long addr)
    +{
    + return find_vma_intersection(mm, addr, addr + 1);
    +}
    +
    static inline unsigned long vm_start_gap(struct vm_area_struct *vma)
    {
    unsigned long vm_start = vma->vm_start;
    --
    2.30.2
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