linux-kernel - [PATCH 3.16.y-ckt 130/180] mm/hugetlb: use pmd_page() in follow_huge

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Message-Id: <1430991989-23170-131-git-send-email-luis.henriques@canonical.com>
Date:	Thu,  7 May 2015 10:45:39 +0100
From:	Luis Henriques <luis.henriques@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Gerald Schaefer <gerald.schaefer@...ibm.com>,
	Hugh Dickins <hughd@...gle.com>, Michal Hocko <mhocko@...e.cz>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Luis Henriques <luis.henriques@...onical.com>
Subject: [PATCH 3.16.y-ckt 130/180] mm/hugetlb: use pmd_page() in follow_huge_pmd()

3.16.7-ckt11 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Gerald Schaefer <gerald.schaefer@...ibm.com>

commit 97534127012f0e396eddea4691f4c9b170aed74b upstream.

Commit 61f77eda9bbf ("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 that commit have pmd_page()
defined, so this should not break anything on other architectures.

Fixes: 61f77eda "mm/hugetlb: reduce arch dependent code around follow_huge_*"
Signed-off-by: Gerald Schaefer <gerald.schaefer@...ibm.com>
Acked-by: Naoya Horiguchi <n-horiguchi@...jp.nec.com>
Cc: Hugh Dickins <hughd@...gle.com>
Cc: Michal Hocko <mhocko@...e.cz>, Andrea Arcangeli <aarcange@...hat.com>
Cc: Martin Schwidefsky <schwidefsky@...ibm.com>
Acked-by: David Rientjes <rientjes@...gle.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Luis Henriques <luis.henriques@...onical.com>
---
 mm/hugetlb.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 5f217e906ff9..1e080a06e6ba 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -3723,8 +3723,7 @@ retry:
 	if (!pmd_huge(*pmd))
 		goto out;
 	if (pmd_present(*pmd)) {
-		page = pte_page(*(pte_t *)pmd) +
-			((address & ~PMD_MASK) >> PAGE_SHIFT);
+		page = pmd_page(*pmd) + ((address & ~PMD_MASK) >> PAGE_SHIFT);
 		if (flags & FOLL_GET)
 			get_page(page);
 	} else {
--
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