workqueue: Replace pwq_activate_inactive_work() with [__]pwq_activate_work()

To prepare for unbound nr_active handling improvements, move work activation
part of pwq_activate_inactive_work() into __pwq_activate_work() and add
pwq_activate_work() which tests WORK_STRUCT_INACTIVE and updates nr_active.

pwq_activate_first_inactive() and try_to_grab_pending() are updated to use
pwq_activate_work(). The latter conversion is functionally identical. For
the former, this conversion adds an unnecessary WORK_STRUCT_INACTIVE
testing. This is temporary and will be removed by the next patch.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Lai Jiangshan <jiangshanlai@gmail.com>

kernel/workqueue.c

@@ -1465,16 +1465,36 @@ static bool pwq_is_empty(struct pool_workqueue *pwq)
 	return !pwq->nr_active && list_empty(&pwq->inactive_works);
 }
 
-static void pwq_activate_inactive_work(struct work_struct *work)
+static void __pwq_activate_work(struct pool_workqueue *pwq,
+				struct work_struct *work)
 {
-	struct pool_workqueue *pwq = get_work_pwq(work);
-
 	trace_workqueue_activate_work(work);
 	if (list_empty(&pwq->pool->worklist))
 		pwq->pool->watchdog_ts = jiffies;
 	move_linked_works(work, &pwq->pool->worklist, NULL);
 	__clear_bit(WORK_STRUCT_INACTIVE_BIT, work_data_bits(work));
+}
+
+/**
+ * pwq_activate_work - Activate a work item if inactive
+ * @pwq: pool_workqueue @work belongs to
+ * @work: work item to activate
+ *
+ * Returns %true if activated. %false if already active.
+ */
+static bool pwq_activate_work(struct pool_workqueue *pwq,
+			      struct work_struct *work)
+{
+	struct worker_pool *pool = pwq->pool;
+
+	lockdep_assert_held(&pool->lock);
+
+	if (!(*work_data_bits(work) & WORK_STRUCT_INACTIVE))
+		return false;
+
 	pwq->nr_active++;
+	__pwq_activate_work(pwq, work);
+	return true;
 }
 
 static void pwq_activate_first_inactive(struct pool_workqueue *pwq)
@@ -1482,7 +1502,7 @@ static void pwq_activate_first_inactive(struct pool_workqueue *pwq)
 	struct work_struct *work = list_first_entry(&pwq->inactive_works,
 						    struct work_struct, entry);
 
-	pwq_activate_inactive_work(work);
+	pwq_activate_work(pwq, work);
 }
 
 /**
@@ -1620,8 +1640,7 @@ static int try_to_grab_pending(struct work_struct *work, bool is_dwork,
 		 * management later on and cause stall.  Make sure the work
 		 * item is activated before grabbing.
 		 */
-		if (*work_data_bits(work) & WORK_STRUCT_INACTIVE)
-			pwq_activate_inactive_work(work);
+		pwq_activate_work(pwq, work);
 
 		list_del_init(&work->entry);
 		pwq_dec_nr_in_flight(pwq, *work_data_bits(work));