[PATCH v2] sparc64: Fix gup_huge_pmd

From	Nitin Gupta <nitin.m.gupta@oracle.com>
Newsgroups	linux.kernel
Subject	[PATCH v2] sparc64: Fix gup_huge_pmd
Date	2017-06-23 02:20 +0200
Message-ID	<tVkul-3lB-5@gated-at.bofh.it> (permalink)
Organization	linux.* mail to news gateway

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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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[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

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