From 69b62d01ec44fe0d505d89917392347732135a4d Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Mon, 17 May 2010 12:51:03 +0200 Subject: [PATCH] writeback: disable periodic old data writeback for !dirty_writeback_centisecs Prior to 2.6.32, setting /proc/sys/vm/dirty_writeback_centisecs disabled periodic dirty writeback from kupdate. This got broken and now causes excessive sys CPU usage if set to zero, as we'll keep beating on schedule(). Cc: stable@kernel.org Reported-by: Justin Maggard Signed-off-by: Jens Axboe --- fs/fs-writeback.c | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-) diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c index 4b37f7cea4dd..760dc8d0b4ff 100644 --- a/fs/fs-writeback.c +++ b/fs/fs-writeback.c @@ -852,6 +852,12 @@ static long wb_check_old_data_flush(struct bdi_writeback *wb) unsigned long expired; long nr_pages; + /* + * When set to zero, disable periodic writeback + */ + if (!dirty_writeback_interval) + return 0; + expired = wb->last_old_flush + msecs_to_jiffies(dirty_writeback_interval * 10); if (time_before(jiffies, expired)) @@ -947,8 +953,12 @@ int bdi_writeback_task(struct bdi_writeback *wb) break; } - wait_jiffies = msecs_to_jiffies(dirty_writeback_interval * 10); - schedule_timeout_interruptible(wait_jiffies); + if (dirty_writeback_interval) { + wait_jiffies = msecs_to_jiffies(dirty_writeback_interval * 10); + schedule_timeout_interruptible(wait_jiffies); + } else + schedule(); + try_to_freeze(); }