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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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