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SubjectRe: [PATCH 3/5] track the root (oldest) anon_vma
On 05/12/2010 04:59 PM, Mel Gorman wrote:
> On Wed, May 12, 2010 at 01:39:58PM -0400, Rik van Riel wrote:
>> Subject: track the root (oldest) anon_vma
>>
>> Track the root (oldest) anon_vma in each anon_vma tree. Because we only
>> take the lock on the root anon_vma, we cannot use the lock on higher-up
>> anon_vmas to lock anything. This makes it impossible to do an indirect
>> lookup of the root anon_vma, since the data structures could go away from
>> under us.
>>
>> However, a direct pointer is safe because the root anon_vma is always the
>> last one that gets freed on munmap or exit, by virtue of the same_vma list
>> order and unlink_anon_vmas walking the list forward.
>>
>
> Shouldn't this be "usually the last one that gets freed" because of the
> ref-counting by KSM aspect? Minor nit anyway.

It needs to be the last one that gets freed. Patch 5/5 makes
sure that it is when KSM refcounting is involved.

>> Signed-off-by: Rik van Riel<riel@redhat.com>
>
> Otherwise
>
> Acked-by: Mel Gorman<mel@csn.ul.ie>

Thank you for reviewing these patches.

--
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