[PATCH v2 3/4] sparc64: Fix gup_huge_pmd

From	Nitin Gupta <nitin.m.gupta@oracle.com>
Newsgroups	linux.kernel
Subject	[PATCH v2 3/4] sparc64: Fix gup_huge_pmd
Date	2017-06-20 00:00 +0200
Message-ID	<tUcSe-8dc-11@gated-at.bofh.it> (permalink)
References	<tUcIy-89O-15@gated-at.bofh.it>
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.

Signed-off-by: Nitin Gupta <nitin.m.gupta@oracle.com>
---
 arch/sparc/mm/gup.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/sparc/mm/gup.c b/arch/sparc/mm/gup.c
index 7cfa9c5..b1c649d 100644
--- a/arch/sparc/mm/gup.c
+++ b/arch/sparc/mm/gup.c
@@ -80,6 +80,8 @@ static int gup_huge_pmd(pmd_t *pmdp, pmd_t pmd, unsigned long addr,
 	refs = 0;
 	head = pmd_page(pmd);
 	page = head + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
+	if (PageTail(head))
+		head = compound_head(head);
 	do {
 		VM_BUG_ON(compound_head(page) != head);
 		pages[*nr] = page;
-- 
2.9.2

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[PATCH v2 3/4] sparc64: Fix gup_huge_pmd Nitin Gupta <nitin.m.gupta@oracle.com> - 2017-06-20 00:00 +0200

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