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SubjectRe: [patch] mmap: feed back correct prev vma when finding vma
On Thu, 9 Aug 2012, Hillf Danton wrote:
> After walking rb tree, if vma is determined, prev vma has to be determined
> based on vma; and rb_prev should be considered only if no vma determined.

Why? Because you think more code is better code? I disagree.

If you have seen a bug here, please tell how to reproduce it.

I have not heard of a bug here: I think you're saying, if the rbtree
were inconsistent with the vma list, then you think it would be a good
idea to believe the vma list instead of the rbtree where there's a choice.

But the rbtree had better not be inconsistent with the vma list.

Hugh

>
> Signed-off-by: Hillf Danton <dhillf@gmail.com>
> ---
>
> --- a/mm/mmap.c Fri Aug 3 07:38:10 2012
> +++ b/mm/mmap.c Mon Aug 6 20:10:18 2012
> @@ -385,9 +385,13 @@ find_vma_prepare(struct mm_struct *mm, u
> }
> }
>
> - *pprev = NULL;
> - if (rb_prev)
> - *pprev = rb_entry(rb_prev, struct vm_area_struct, vm_rb);
> + if (vma) {
> + *pprev = vma->vm_prev;
> + } else {
> + *pprev = NULL;
> + if (rb_prev)
> + *pprev = rb_entry(rb_prev, struct vm_area_struct, vm_rb);
> + }
> *rb_link = __rb_link;
> *rb_parent = __rb_parent;
> return vma;
> --


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