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    Subject[PATCH v10 11/69] mm/mmap: use the maple tree in find_vma() instead of the rbtree.
    Date
    From: "Liam R. Howlett" <Liam.Howlett@Oracle.com>

    Using the maple tree interface mt_find() will handle the RCU locking and
    will start searching at the address up to the limit, ULONG_MAX in this
    case.

    Add kernel documentation to this API.

    Link: https://lkml.kernel.org/r/20220504010716.661115-13-Liam.Howlett@oracle.com
    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: "Matthew Wilcox (Oracle)" <willy@infradead.org>
    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 | 28 ++++++++++------------------
    1 file changed, 10 insertions(+), 18 deletions(-)

    diff --git a/mm/mmap.c b/mm/mmap.c
    index d7e6baa2f40f..fdb61252448f 100644
    --- a/mm/mmap.c
    +++ b/mm/mmap.c
    @@ -2486,11 +2486,18 @@ get_unmapped_area(struct file *file, unsigned long addr, unsigned long len,

    EXPORT_SYMBOL(get_unmapped_area);

    -/* Look up the first VMA which satisfies addr < vm_end, NULL if none. */
    +/**
    + * find_vma() - Find the VMA for a given address, or the next vma.
    + * @mm: The mm_struct to check
    + * @addr: The address
    + *
    + * 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(struct mm_struct *mm, unsigned long addr)
    {
    - struct rb_node *rb_node;
    struct vm_area_struct *vma;
    + unsigned long index = addr;

    mmap_assert_locked(mm);
    /* Check the cache first. */
    @@ -2498,22 +2505,7 @@ struct vm_area_struct *find_vma(struct mm_struct *mm, unsigned long addr)
    if (likely(vma))
    return vma;

    - rb_node = mm->mm_rb.rb_node;
    -
    - while (rb_node) {
    - struct vm_area_struct *tmp;
    -
    - tmp = rb_entry(rb_node, struct vm_area_struct, vm_rb);
    -
    - if (tmp->vm_end > addr) {
    - vma = tmp;
    - if (tmp->vm_start <= addr)
    - break;
    - rb_node = rb_node->rb_left;
    - } else
    - rb_node = rb_node->rb_right;
    - }
    -
    + vma = mt_find(&mm->mm_mt, &index, ULONG_MAX);
    if (vma)
    vmacache_update(addr, vma);
    return vma;
    --
    2.35.1
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