[PATCH v3 3/4] sparc64: Fix gup_huge_pmd

[Nitin Gupta <nitin.m.gupta@oracle.com>]

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