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

[KOSAKI Motohiro]

(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@xxxxxxxxxxxxxx>  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).




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