sparc64: Fix gup_huge_pmd

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>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 2 deletions

diff --git a/arch/sparc/mm/gup.c b/arch/sparc/mm/gup.c
index cd0e32bbcb1d..f80cfc64c55b 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;