From: Michal Hocko <mhocko@kernel.org>
To: Wei Yang <richard.weiyang@gmail.com>
Cc: akpm@linux-foundation.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mm/vmalloc: a slight change of compare target in __insert_vmap_area()
Date: Thu, 25 May 2017 07:39:35 +0200 [thread overview]
Message-ID: <20170525053935.GA12721@dhcp22.suse.cz> (raw)
In-Reply-To: <20170524150730.GA8445@WeideMacBook-Pro.local>
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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next prev parent reply other threads:[~2017-05-25 5:39 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-05-24 10:03 Wei Yang
2017-05-24 12:11 ` Michal Hocko
2017-05-24 15:07 ` Wei Yang
2017-05-25 5:39 ` Michal Hocko [this message]
2017-05-25 3:04 ` zhong jiang
2017-05-26 1:36 ` Wei Yang
2017-05-26 1:55 ` zhong jiang
2017-06-02 1:45 ` Wei Yang
2017-06-02 2:26 ` zhong jiang
2017-06-03 2:28 ` Wei Yang
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