diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 4c33705489825a..7439ecd44ac9e4 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -406,6 +406,11 @@ static bool inode_do_switch_wbs(struct inode *inode,
 		inc_wb_stat(new_wb, WB_WRITEBACK);
 	}
 
+	if (mapping_tagged(mapping, PAGECACHE_TAG_WRITEBACK)) {
+		atomic_dec(&old_wb->writeback_inodes);
+		atomic_inc(&new_wb->writeback_inodes);
+	}
+
 	wb_get(new_wb);
 
 	/*
diff --git a/include/linux/backing-dev-defs.h b/include/linux/backing-dev-defs.h
index 1d7edad9914fc5..06fb8e13f6bc51 100644
--- a/include/linux/backing-dev-defs.h
+++ b/include/linux/backing-dev-defs.h
@@ -116,6 +116,7 @@ struct bdi_writeback {
 	struct list_head b_dirty_time;	/* time stamps are dirty */
 	spinlock_t list_lock;		/* protects the b_* lists */
 
+	atomic_t writeback_inodes;	/* number of inodes under writeback */
 	struct percpu_counter stat[NR_WB_STAT_ITEMS];
 
 	unsigned long congested;	/* WB_[a]sync_congested flags */
diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index f5561ea7d90ad6..b4c707ddedb1b4 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -293,6 +293,7 @@ static int wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi,
 	INIT_LIST_HEAD(&wb->b_dirty_time);
 	spin_lock_init(&wb->list_lock);
 
+	atomic_set(&wb->writeback_inodes, 0);
 	wb->bw_time_stamp = jiffies;
 	wb->balanced_dirty_ratelimit = INIT_BW;
 	wb->dirty_ratelimit = INIT_BW;
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 9f63548f247c33..e1aa1c9d8e3629 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -2731,6 +2731,16 @@ int clear_page_dirty_for_io(struct page *page)
 }
 EXPORT_SYMBOL(clear_page_dirty_for_io);
 
+static void wb_inode_writeback_start(struct bdi_writeback *wb)
+{
+	atomic_inc(&wb->writeback_inodes);
+}
+
+static void wb_inode_writeback_end(struct bdi_writeback *wb)
+{
+	atomic_dec(&wb->writeback_inodes);
+}
+
 int test_clear_page_writeback(struct page *page)
 {
 	struct address_space *mapping = page_mapping(page);
@@ -2752,6 +2762,9 @@ int test_clear_page_writeback(struct page *page)
 
 				dec_wb_stat(wb, WB_WRITEBACK);
 				__wb_writeout_inc(wb);
+				if (!mapping_tagged(mapping,
+						    PAGECACHE_TAG_WRITEBACK))
+					wb_inode_writeback_end(wb);
 			}
 		}
 
@@ -2794,8 +2807,13 @@ int __test_set_page_writeback(struct page *page, bool keep_write)
 						   PAGECACHE_TAG_WRITEBACK);
 
 			xas_set_mark(&xas, PAGECACHE_TAG_WRITEBACK);
-			if (bdi->capabilities & BDI_CAP_WRITEBACK_ACCT)
-				inc_wb_stat(inode_to_wb(inode), WB_WRITEBACK);
+			if (bdi->capabilities & BDI_CAP_WRITEBACK_ACCT) {
+				struct bdi_writeback *wb = inode_to_wb(inode);
+
+				inc_wb_stat(wb, WB_WRITEBACK);
+				if (!on_wblist)
+					wb_inode_writeback_start(wb);
+			}
 
 			/*
 			 * We can come through here when swapping anonymous