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Re: [PATCH] mm/vmalloc: a slight change of compare target in __insert_vmap_area()

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On Wed 24-05-17 23:07:30, Wei Yang wrote:
> On Wed, May 24, 2017 at 02:11:35PM +0200, Michal Hocko wrote:
> >On Wed 24-05-17 18:03:47, Wei Yang wrote:
> >> The vmap RB tree store the elements in order and no overlap between any of
> >> them. The comparison in __insert_vmap_area() is to decide which direction
> >> the search should follow and make sure the new vmap_area is not overlap
> >> with any other.
> >> 
> >> Current implementation fails to do the overlap check.
> >> 
> >> When first "if" is not true, it means
> >> 
> >>     va->va_start >= tmp_va->va_end
> >> 
> >> And with the truth
> >> 
> >>     xxx->va_end > xxx->va_start
> >> 
> >> The deduction is
> >> 
> >>     va->va_end > tmp_va->va_start
> >> 
> >> which is the condition in second "if".
> >> 
> >> This patch changes a little of the comparison in __insert_vmap_area() to
> >> make sure it forbids the overlapped vmap_area.
> >
> >Why do we care about overlapping vmap areas at this level. This is an
> >internal function and all the sanity checks should have been done by
> >that time AFAIR. Could you describe the problem which you are trying to
> >fix/address?
> >
> 
> No problem it tries to fix.

I would prefer the not touch the code if there is no problem to fix.
-- 
Michal Hocko
SUSE Labs

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[PATCH] mm/vmalloc: a slight change of compare target in __insert_vmap_area() Wei Yang <richard.weiyang@gmail.com> - 2017-05-24 12:10 +0200
  Re: [PATCH] mm/vmalloc: a slight change of compare target in  __insert_vmap_area() Michal Hocko <mhocko@kernel.org> - 2017-05-24 14:20 +0200
    Re: [PATCH] mm/vmalloc: a slight change of compare target in  __insert_vmap_area() Wei Yang <richard.weiyang@gmail.com> - 2017-05-24 17:10 +0200
      Re: [PATCH] mm/vmalloc: a slight change of compare target in  __insert_vmap_area() Michal Hocko <mhocko@kernel.org> - 2017-05-25 07:40 +0200
  Re: [PATCH] mm/vmalloc: a slight change of compare target in __insert_vmap_area() zhong jiang <zhongjiang@huawei.com> - 2017-05-25 05:10 +0200
    Re: [PATCH] mm/vmalloc: a slight change of compare target in  __insert_vmap_area() Wei Yang <richard.weiyang@gmail.com> - 2017-05-26 03:40 +0200
      Re: [PATCH] mm/vmalloc: a slight change of compare target in __insert_vmap_area() zhong jiang <zhongjiang@huawei.com> - 2017-05-26 04:10 +0200
        Re: [PATCH] mm/vmalloc: a slight change of compare target in  __insert_vmap_area() Wei Yang <richard.weiyang@gmail.com> - 2017-06-02 03:50 +0200
          Re: [PATCH] mm/vmalloc: a slight change of compare target in __insert_vmap_area() zhong jiang <zhongjiang@huawei.com> - 2017-06-02 04:30 +0200
            Re: [PATCH] mm/vmalloc: a slight change of compare target in  __insert_vmap_area() Wei Yang <richard.weiyang@gmail.com> - 2017-06-03 04:30 +0200

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