On 8/9/19 2:19 AM, Wei Yang wrote:
> When addr is out of the range of the whole rb_tree, pprev will points to
> the right-most node. rb_tree facility already provides a helper
> function, rb_last, to do this task. We can leverage this instead of
> re-implement it.
>
> This patch refines find_vma_prev with rb_last to make it a little nicer
> to read.
>
> Signed-off-by: Wei Yang <richardw.yang@xxxxxxxxxxxxxxx>
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
Nit below:
> ---
> v2: leverage rb_last
> ---
> mm/mmap.c | 9 +++------
> 1 file changed, 3 insertions(+), 6 deletions(-)
>
> diff --git a/mm/mmap.c b/mm/mmap.c
> index 7e8c3e8ae75f..f7ed0afb994c 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -2270,12 +2270,9 @@ find_vma_prev(struct mm_struct *mm, unsigned long addr,
> if (vma) {
> *pprev = vma->vm_prev;
> } else {
> - struct rb_node *rb_node = mm->mm_rb.rb_node;
> - *pprev = NULL;
> - while (rb_node) {
> - *pprev = rb_entry(rb_node, struct vm_area_struct, vm_rb);
> - rb_node = rb_node->rb_right;
> - }
> + struct rb_node *rb_node = rb_last(&mm->mm_rb);
> + *pprev = !rb_node ? NULL :
> + rb_entry(rb_node, struct vm_area_struct, vm_rb);
It's perhaps more common to write it like:
*pprev = rb_node ? rb_entry(rb_node, struct vm_area_struct, vm_rb) : NULL;
> }
> return vma;
> }
>
