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[PATCH v2] sparc64: Fix gup_huge_pmd

Started byNitin Gupta <nitin.m.gupta@oracle.com>
First post2017-06-23 02:20 +0200
Last post2017-06-25 21:30 +0200
Articles 2 — 2 participants

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  [PATCH v2] sparc64: Fix gup_huge_pmd Nitin Gupta <nitin.m.gupta@oracle.com> - 2017-06-23 02:20 +0200
    Re: [PATCH v2] sparc64: Fix gup_huge_pmd David Miller <davem@davemloft.net> - 2017-06-25 21:30 +0200

#1673147 — [PATCH v2] sparc64: Fix gup_huge_pmd

FromNitin Gupta <nitin.m.gupta@oracle.com>
Date2017-06-23 02:20 +0200
Subject[PATCH v2] sparc64: Fix gup_huge_pmd
Message-ID<tVkul-3lB-5@gated-at.bofh.it>
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>
---
 Changes since v1
 - Clarify use of 'head' variable (Julian Calaby)

 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 cd0e32b..f80cfc6 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;
 
 	refs = 0;
-	head = pmd_page(pmd);
-	page = head + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
+	page = pmd_page(pmd) + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
+	head = compound_head(page);
 	do {
 		VM_BUG_ON(compound_head(page) != head);
 		pages[*nr] = page;
-- 
2.9.2

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#1674288

FromDavid Miller <davem@davemloft.net>
Date2017-06-25 21:30 +0200
Message-ID<tWlom-Ea-13@gated-at.bofh.it>
In reply to#1673147
From: Nitin Gupta <nitin.m.gupta@oracle.com>
Date: Thu, 22 Jun 2017 17:15:08 -0700

> 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>
> ---
>  Changes since v1
>  - Clarify use of 'head' variable (Julian Calaby)

Applied and queued up for -stable, thanks.

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