Re: [Resend PATCH v2] mm: Fix slab->page _count corruption.

[Pravin Shelar <pshelar@xxxxxxxxxx>]

On Fri, Jun 8, 2012 at 2:19 PM, Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote:
> On Fri, 8 Jun 2012 13:23:56 -0700
> Pravin Shelar <pshelar@xxxxxxxxxx> wrote:
>
>> On Fri, Jun 8, 2012 at 1:15 PM, Christoph Lameter <cl@xxxxxxxxx> wrote:
>> > On Fri, 8 Jun 2012, Andrew Morton wrote:
>> >
>> >> OK. __I assume this bug has been there for quite some time.
>> >
>> > Well the huge pages refcount tricks caused the issue.
>> >
>> >> How serious is it? __Have people been reporting it in real workloads?
>> >> How to trigger it? __IOW, does this need -stable backporting?
>> >
>> > Possibly.
>>
>> If this patch is getting back-ported then we shld also do same for
>> 5bf5f03c271907978 (mm: fix slab->page flags corruption) which fixes
>> other issue related to slub  and huge page sharing.
>
> Well I don't know if either are getting backported yet.
>
> To decide that we would have to understand the end-user impact of the
> bug(s).  Please tell us?
>

We are working on zero copy io over skb in Open-vswitch. thats when we
so this panic when we tried to get_page() over skb linear data
allocated slub. But then I realized that it could potentially affect
other subsystems as well, e.g. xfs and ocfs, which does page struct
updates on slub objects.

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