1 files changed, 46 insertions, 2 deletions

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 92aaf641ee22..508e10cc3fcd 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -198,6 +198,41 @@ int inode_congested(struct inode *inode, int cong_bits)
 }
 EXPORT_SYMBOL_GPL(inode_congested);
 
+/**
+ * wb_split_bdi_pages - split nr_pages to write according to bandwidth
+ * @wb: target bdi_writeback to split @nr_pages to
+ * @nr_pages: number of pages to write for the whole bdi
+ *
+ * Split @wb's portion of @nr_pages according to @wb's write bandwidth in
+ * relation to the total write bandwidth of all wb's w/ dirty inodes on
+ * @wb->bdi.
+ */
+static long wb_split_bdi_pages(struct bdi_writeback *wb, long nr_pages)
+{
+	unsigned long this_bw = wb->avg_write_bandwidth;
+	unsigned long tot_bw = atomic_long_read(&wb->bdi->tot_write_bandwidth);
+
+	if (nr_pages == LONG_MAX)
+		return LONG_MAX;
+
+	/*
+	 * This may be called on clean wb's and proportional distribution
+	 * may not make sense, just use the original @nr_pages in those
+	 * cases.  In general, we wanna err on the side of writing more.
+	 */
+	if (!tot_bw || this_bw >= tot_bw)
+		return nr_pages;
+	else
+		return DIV_ROUND_UP_ULL((u64)nr_pages * this_bw, tot_bw);
+}
+
+#else	/* CONFIG_CGROUP_WRITEBACK */
+
+static long wb_split_bdi_pages(struct bdi_writeback *wb, long nr_pages)
+{
+	return nr_pages;
+}
+
 #endif	/* CONFIG_CGROUP_WRITEBACK */
 
 void wb_start_writeback(struct bdi_writeback *wb, long nr_pages,
@@ -1187,8 +1222,17 @@ void wakeup_flusher_threads(long nr_pages, enum wb_reason reason)
 		nr_pages = get_nr_dirty_pages();
 
 	rcu_read_lock();
-	list_for_each_entry_rcu(bdi, &bdi_list, bdi_list)
-		wb_start_writeback(&bdi->wb, nr_pages, false, reason);
+	list_for_each_entry_rcu(bdi, &bdi_list, bdi_list) {
+		struct bdi_writeback *wb;
+		struct wb_iter iter;
+
+		if (!bdi_has_dirty_io(bdi))
+			continue;
+
+		bdi_for_each_wb(wb, bdi, &iter, 0)
+			wb_start_writeback(wb, wb_split_bdi_pages(wb, nr_pages),
+					   false, reason);
+	}
 	rcu_read_unlock();
 }