[PATCH] fix extra page ref count in follow_hugetlb_page

git-commit: d5d4b0aa4e1430d73050babba999365593bdb9d2
"[PATCH] optimize follow_hugetlb_page" breaks mlock on hugepage areas.

I mis-interpret pages argument and made get_page() unconditional.  It
should only get a ref count when "pages" argument is non-null.

Credit goes to Adam Litke who spotted the bug.

Signed-off-by: Ken Chen <kenneth.w.chen@intel.com>
Acked-by: Adam Litke <agl@us.ibm.com>
Cc: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 3 insertions, 2 deletions

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index ebad6bbb3501..d87885eb4acc 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -697,9 +697,10 @@ int follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
                 pfn_offset = (vaddr & ~HPAGE_MASK) >> PAGE_SHIFT;
                 page = pte_page(*pte);
 same_page:
-                get_page(page);
-                if (pages)
+                if (pages) {
+                        get_page(page);
                         pages[i] = page + pfn_offset;
+                }
 
                 if (vmas)
                         vmas[i] = vma;