Re: [PATCH] mm/hugetlb: use pmd_page() in follow_huge_pmd()

[David Rientjes <rientjes@google.com>]

On Thu, 9 Apr 2015, Gerald Schaefer wrote:

> commit 61f77eda "mm/hugetlb: reduce arch dependent code around follow_huge_*"
> broke follow_huge_pmd() on s390, where pmd and pte layout differ and using
> pte_page() on a huge pmd will return wrong results. Using pmd_page() instead
> fixes this.
> 
> All architectures that were touched by commit 61f77eda have pmd_page()
> defined, so this should not break anything on other architectures.
> 
> Signed-off-by: Gerald Schaefer <gerald.schaefer@de.ibm.com>
> Cc: stable@vger.kernel.org # v3.12

Acked-by: David Rientjes <rientjes@google.com>

I'm not sure where the stable cc came from, though: commit 61f77eda makes 
s390 use a generic version of follow_huge_pmd() and that generic version 
is buggy for s930 because of commit e66f17ff7177 ("mm/hugetlb: take page 
table lock in follow_huge_pmd()").  Both of those are 4.0 material, 
though, so why is this needed for stable 3.12?

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