Re: [PATCH 0/6] mempolicy memory corruption fixlet

[KOSAKI Motohiro <kosaki.motohiro@gmail.com>]

(5/30/12 5:22 PM), Ben Hutchings wrote:
> On Wed, May 30, 2012 at 04:00:55PM -0400, KOSAKI Motohiro wrote:
>> On Wed, May 30, 2012 at 3:52 PM, Andi Kleen<andi@firstfloor.org>  wrote:
>>> On Wed, May 30, 2012 at 02:42:42PM -0500, Christoph Lameter wrote:
>>>> On Wed, 30 May 2012, Andi Kleen wrote:
>>>>
>>>>> On Wed, May 30, 2012 at 01:50:02PM -0500, Christoph Lameter wrote:
>>>>>> On Wed, 30 May 2012, Andi Kleen wrote:
>>>>>>
>>>>>>> I always regretted that cpusets were no done with custom node lists.
>>>>>>> That would have been much cleaner and also likely faster than what we have.
>>>>>>
>>>>>> Could shared memory policies ignore cpuset constraints?
>>>>>
>>>>> Only if noone uses cpusets as a "security" mechanism, just for a "soft policy"
>>>>> Even with soft policy you could well break someone's setup.
>>>>
>>>> Well at least lets exempt shared memory from memory migration and memory
>>>> policy updates. That seems to be causing many of these issues.
>>>
>>> Migration on the page level is needed for the memory error handling.
>>>
>>> Updates: you mean not allowing to set the policy when there are already
>>> multiple mappers? I could see that causing some unexpected behaviour. Presumably
>>> a standard database will only set it at the beginning, but I don't know
>>> if that would work for all users.
>>
>> We don't need to kill migration core. We only need to kill that mbind(2) updates
>> vma->policy of shmem.
> [...]
>
> So should I (and Greg) drop 'mm: mempolicy: Let vma_merge and
> vma_split handle vma->vm_policy linkages' from the pending stable
> releases?  Or is that OK as an interim fix until these changes go
> into mainline?

Please drop. It screw up mbind(2).