[PATCH v2] sparc64: Fix gup_huge_pmd

From: Nitin Gupta
Date: Thu Jun 22 2017 - 20:17:24 EST


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@xxxxxxxxx>
Signed-off-by: Nitin Gupta <nitin.m.gupta@xxxxxxxxxx>
---
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