diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 67210bae5cd0..76597dd8cfe8 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -530,8 +530,6 @@ static void inode_switch_wbs(struct inode *inode, int new_wb_id)
 	ihold(inode);
 	isw->inode = inode;
 
-	atomic_inc(&isw_nr_in_flight);
-
 	/*
 	 * In addition to synchronizing among switchers, I_WB_SWITCH tells
 	 * the RCU protected stat update paths to grab the mapping's
@@ -539,6 +537,9 @@ static void inode_switch_wbs(struct inode *inode, int new_wb_id)
 	 * Let's continue after I_WB_SWITCH is guaranteed to be visible.
 	 */
 	call_rcu(&isw->rcu_head, inode_switch_wbs_rcu_fn);
+
+	atomic_inc(&isw_nr_in_flight);
+
 	goto out_unlock;
 
 out_free:
@@ -910,7 +911,11 @@ restart:
 void cgroup_writeback_umount(void)
 {
 	if (atomic_read(&isw_nr_in_flight)) {
-		synchronize_rcu();
+		/*
+		 * Use rcu_barrier() to wait for all pending callbacks to
+		 * ensure that all in-flight wb switches are in the workqueue.
+		 */
+		rcu_barrier();
 		flush_workqueue(isw_wq);
 	}
 }