Re: [PATCH] nommu page refcount bug fixing

[Nick Piggin]

Luke Yang wrote:

> Hi all,
>
>   The previous "nommu use compound pages" patch has a problem: when
> the pages allocated is not compound page (eg: slab allocator), the
> refcount value of every page still need to be set, otherwise the
> get/put_page() would free a single page improperly, such as in
> access_process_vm().

Yep, sorry this slipped into the kernel. It's my fault for not giving
Andrew a fix for it.

As you might know, page refcounting in nommu was already broken, so
I'm working on a proper solution to fix it.

In the meantime though, this is a step backwards and reintroduces
NOMMU special-casing in page refcounting. As a temporary fix, what I
think should happen is simply for all slab allocations to ask for
__GFP_COMP pages.

Could you check that fixes your problem?

Thanks,
Nick

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