1 files changed, 18 insertions, 18 deletions

diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 0b9c5cbe8eba..c518c845f202 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -1972,31 +1972,31 @@ bool wb_over_bg_thresh(struct bdi_writeback *wb)
 int dirty_writeback_centisecs_handler(struct ctl_table *table, int write,
         void __user *buffer, size_t *length, loff_t *ppos)
 {
-        proc_dointvec(table, write, buffer, length, ppos);
-        return 0;
+        unsigned int old_interval = dirty_writeback_interval;
+        int ret;
+
+        ret = proc_dointvec(table, write, buffer, length, ppos);
+
+        /*
+         * Writing 0 to dirty_writeback_interval will disable periodic writeback
+         * and a different non-zero value will wakeup the writeback threads.
+         * wb_wakeup_delayed() would be more appropriate, but it's a pain to
+         * iterate over all bdis and wbs.
+         * The reason we do this is to make the change take effect immediately.
+         */
+        if (!ret && write && dirty_writeback_interval &&
+                dirty_writeback_interval != old_interval)
+                wakeup_flusher_threads(WB_REASON_PERIODIC);
+
+        return ret;
 }
 
 #ifdef CONFIG_BLOCK
 void laptop_mode_timer_fn(unsigned long data)
 {
         struct request_queue *q = (struct request_queue *)data;
-        int nr_pages = global_node_page_state(NR_FILE_DIRTY) +
-                global_node_page_state(NR_UNSTABLE_NFS);
-        struct bdi_writeback *wb;
 
-        /*
-         * We want to write everything out, not just down to the dirty
-         * threshold
-         */
-        if (!bdi_has_dirty_io(q->backing_dev_info))
-                return;
-
-        rcu_read_lock();
-        list_for_each_entry_rcu(wb, &q->backing_dev_info->wb_list, bdi_node)
-                if (wb_has_dirty_io(wb))
-                        wb_start_writeback(wb, nr_pages, true,
-                                           WB_REASON_LAPTOP_TIMER);
-        rcu_read_unlock();
+        wakeup_flusher_threads_bdi(q->backing_dev_info, WB_REASON_LAPTOP_TIMER);
 }
 
 /*