On Tue, Feb 25, 2014 at 11:29:13PM +0100, Jan Kara wrote: > From: Derek Basehore <dbasehore@xxxxxxxxxxxx> > > bdi_wakeup_thread_delayed() used the mod_delayed_work() function to > schedule work to writeback dirty inodes. The problem with this is that > it can delay work that is scheduled for immediate execution, such as the > work from sync_inodes_sb(). This can happen since mod_delayed_work() > can now steal work from a work_queue. This fixes the problem by using > queue_delayed_work() instead. This is a regression caused by > 839a8e8660b6 "writeback: replace custom worker pool implementation with > unbound workqueue". > > The reason that this causes a problem is that laptop-mode will change > the delay, dirty_writeback_centisecs, to 60000 (10 minutes) by default. > In the case that bdi_wakeup_thread_delayed() races with > sync_inodes_sb(), sync will be stopped for 10 minutes and trigger a hung > task. Even if dirty_writeback_centisecs is not long enough to cause a > hung task, we still don't want to delay sync for that long. > > We fix the problem by using queue_delayed_work() when we want to > schedule writeback sometime in future. This function doesn't change the > timer if it is already armed. > > For the same reason, we also change bdi_writeback_workfn() to > immediately queue the work again in the case that the work_list is not > empty. The same problem can happen if the sync work is run on the rescue > worker. > > Fixes: 839a8e8660b6777e7fe4e80af1a048aebe2b5977 > CC: stable@xxxxxxxxxxxxxxx > Signed-off-by: Derek Basehore <dbasehore@xxxxxxxxxxxx> > Signed-off-by: Jan Kara <jack@xxxxxxx> Reviewed-by: Tejun Heo <tj@xxxxxxxxxx> Thanks. -- tejun -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
