From: Chen, Kenneth W <kenneth.w.chen@intel.com>
Date: Fri, 31 Mar 2006 10:29:57 +0000 (-0800)
Subject: [PATCH] fix extra page ref count in follow_hugetlb_page
X-Git-Tag: v2.6.17-rc1~126
X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=d6692183ac1d8f4a4e4015f9ce9acc2514618e0b;p=linux-2.6

[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>
---

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index ebad6bbb35..d87885eb4a 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;