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From:   Sasha Levin <Alexander.Levin@microsoft.com>
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        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
CC:     Nitin Gupta <nitin.m.gupta@oracle.com>,
        Julian Calaby <julian.calaby@gmail.com>,
        "David S . Miller" <davem@davemloft.net>,
        Sasha Levin <Alexander.Levin@microsoft.com>
Subject: [PATCH AUTOSEL for 4.9 145/293] sparc64: Fix gup_huge_pmd
Thread-Topic: [PATCH AUTOSEL for 4.9 145/293] sparc64: Fix gup_huge_pmd
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Date:   Mon, 9 Apr 2018 00:24:46 +0000
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From: Nitin Gupta <nitin.m.gupta@oracle.com>

[ Upstream commit dbd2667a4fb9ce4f547982b07cd69dda127c47ea ]

The function assumes that each PMD points to head of a
huge page. This is not correct as a PMD can point to
start of any 8M region with a, say 256M, hugepage. The
fix ensures that it points to the correct head of any PMD
huge page.

Cc: Julian Calaby <julian.calaby@gmail.com>
Signed-off-by: Nitin Gupta <nitin.m.gupta@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
---
 arch/sparc/mm/gup.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/sparc/mm/gup.c b/arch/sparc/mm/gup.c
index cd0e32bbcb1d..f80cfc64c55b 100644
--- a/arch/sparc/mm/gup.c
+++ b/arch/sparc/mm/gup.c
@@ -78,8 +78,8 @@ static int gup_huge_pmd(pmd_t *pmdp, pmd_t pmd, unsigned =
long addr,
 		return 0;
=20
 	refs =3D 0;
-	head =3D pmd_page(pmd);
-	page =3D head + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
+	page =3D pmd_page(pmd) + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
+	head =3D compound_head(page);
 	do {
 		VM_BUG_ON(compound_head(page) !=3D head);
 		pages[*nr] =3D page;
--=20
2.15.1