diff --git a/[refs] b/[refs]
index 70a2ddc65ce6..84736c52255f 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 37d81828385f8ff823caaaf1a83e72d065b6cfa1
+refs/heads/master: 9ab772cd535c4b256a577eae516f9c7462346b2d
diff --git a/trunk/include/linux/mutex.h b/trunk/include/linux/mutex.h
index 3069ec7e0ab8..93054fc3635c 100644
--- a/trunk/include/linux/mutex.h
+++ b/trunk/include/linux/mutex.h
@@ -151,4 +151,27 @@ extern int __must_check mutex_lock_killable(struct mutex *lock);
 extern int mutex_trylock(struct mutex *lock);
 extern void mutex_unlock(struct mutex *lock);
 
+/**
+ * atomic_dec_and_mutex_lock - return holding mutex if we dec to 0
+ * @cnt: the atomic which we are to dec
+ * @lock: the mutex to return holding if we dec to 0
+ *
+ * return true and hold lock if we dec to 0, return false otherwise
+ */
+static inline int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock)
+{
+	/* dec if we can't possibly hit 0 */
+	if (atomic_add_unless(cnt, -1, 1))
+		return 0;
+	/* we might hit 0, so take the lock */
+	mutex_lock(lock);
+	if (!atomic_dec_and_test(cnt)) {
+		/* when we actually did the dec, we didn't hit 0 */
+		mutex_unlock(lock);
+		return 0;
+	}
+	/* we hit 0, and we hold the lock */
+	return 1;
+}
+
 #endif