From 976fc1676c22f263ec9cba6a25cf706310e0cf43 Mon Sep 17 00:00:00 2001
From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Date: Mon, 14 Dec 2009 17:59:45 -0800
Subject: [PATCH] --- yaml --- r: 176304 b: refs/heads/master c:
 caed0f486e582eeeb6e3546417fd758230fe4ad9 h: refs/heads/master v: v3

---
 [refs]          |  2 +-
 trunk/mm/rmap.c | 35 ++++++++++++++++++++++-------------
 2 files changed, 23 insertions(+), 14 deletions(-)

diff --git a/[refs] b/[refs]
index 419f915da220..968a275040ce 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 23ce932a5e3ec3b9f06e92c8797d834d43abfb0f
+refs/heads/master: caed0f486e582eeeb6e3546417fd758230fe4ad9
diff --git a/trunk/mm/rmap.c b/trunk/mm/rmap.c
index c81bedd7d527..98135dbd25ba 100644
--- a/trunk/mm/rmap.c
+++ b/trunk/mm/rmap.c
@@ -789,10 +789,9 @@ int try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
 	 * skipped over this mm) then we should reactivate it.
 	 */
 	if (!(flags & TTU_IGNORE_MLOCK)) {
-		if (vma->vm_flags & VM_LOCKED) {
-			ret = SWAP_MLOCK;
-			goto out_unmap;
-		}
+		if (vma->vm_flags & VM_LOCKED)
+			goto out_mlock;
+
 		if (TTU_ACTION(flags) == TTU_MUNLOCK)
 			goto out_unmap;
 	}
@@ -865,18 +864,28 @@ int try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
 
 out_unmap:
 	pte_unmap_unlock(pte, ptl);
+out:
+	return ret;
 
-	if (ret == SWAP_MLOCK) {
-		ret = SWAP_AGAIN;
-		if (down_read_trylock(&vma->vm_mm->mmap_sem)) {
-			if (vma->vm_flags & VM_LOCKED) {
-				mlock_vma_page(page);
-				ret = SWAP_MLOCK;
-			}
-			up_read(&vma->vm_mm->mmap_sem);
+out_mlock:
+	pte_unmap_unlock(pte, ptl);
+
+
+	/*
+	 * We need mmap_sem locking, Otherwise VM_LOCKED check makes
+	 * unstable result and race. Plus, We can't wait here because
+	 * we now hold anon_vma->lock or mapping->i_mmap_lock.
+	 * if trylock failed, the page remain in evictable lru and later
+	 * vmscan could retry to move the page to unevictable lru if the
+	 * page is actually mlocked.
+	 */
+	if (down_read_trylock(&vma->vm_mm->mmap_sem)) {
+		if (vma->vm_flags & VM_LOCKED) {
+			mlock_vma_page(page);
+			ret = SWAP_MLOCK;
 		}
+		up_read(&vma->vm_mm->mmap_sem);
 	}
-out:
 	return ret;
 }