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

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Message-Id: <1428595895-24140-1-git-send-email-gerald.schaefer@de.ibm.com>
Date:	Thu,  9 Apr 2015 18:11:35 +0200
From:	Gerald Schaefer <gerald.schaefer@...ibm.com>
To:	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Hugh Dickins <hughd@...gle.com>
Cc:	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Michal Hocko <mhocko@...e.cz>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Gerald Schaefer <gerald.schaefer@...ibm.com>,
	stable@...r.kernel.org.#.v3.12
Subject: [PATCH] mm/hugetlb: use pmd_page() in follow_huge_pmd()

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
---
 mm/hugetlb.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index e8c92ae..271e443 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -3865,8 +3865,7 @@ 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 {
-- 
2.1.4

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