linux-kernel - Re: [PATCH] mm/hugetlb: use pmd_page() in follow_huge

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Date:	Fri, 10 Apr 2015 10:08:49 +0200
From:	Gerald Schaefer <gerald.schaefer@...ibm.com>
To:	David Rientjes <rientjes@...gle.com>
Cc:	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Hugh Dickins <hughd@...gle.com>, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, Michal Hocko <mhocko@...e.cz>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Jiri Slaby <jslaby@...e.cz>
Subject: Re: [PATCH] mm/hugetlb: use pmd_page() in follow_huge_pmd()

On Thu, 9 Apr 2015 12:41:47 -0700 (PDT)
David Rientjes <rientjes@...gle.com> wrote:

> 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@...ibm.com>
> > Cc: stable@...r.kernel.org # v3.12
> 
> Acked-by: David Rientjes <rientjes@...gle.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?

Both commits 61f77eda and e66f17ff already made it into the 3.12 stable
tree, probably because of SLES 12 (actually that's how I noticed them).

But I guess I screwed up the stable CC, stable@...r.kernel.org.#.v3.12
somehow doesn't look right, not sure if the CC in the patch header
suffices. Looks like Jiri Slaby added the patches to 3.12, putting him
on CC now.

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