Commit 297252c8 authored Jul 25, 2010 by Artem Bityutskiy Committed by Jens Axboe Aug 07, 2010

writeback: do not lose wake-ups in bdi threads



Currently, bdi threads ('bdi_writeback_thread()') can lose wake-ups. For
example, if 'bdi_queue_work()' is executed after the bdi thread have had
finished 'wb_do_writeback()' but before it called
'schedule_timeout_interruptible()'.

To fix this issue, we have to check whether we have works to process after we
have changed the task state to 'TASK_INTERRUPTIBLE'.

This patch also clean-ups handling of the cases when 'dirty_writeback_interval'
is zero or non-zero.

Additionally, this patch also removes unneeded 'list_empty_careful()' call.

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>

parent c4ec7908

fs/fs-writeback.c

+9 −8

Original line number	Diff line number	Diff line
		@@ -848,17 +848,18 @@ int bdi_writeback_thread(void *data)
		break;
		}

		if (dirty_writeback_interval) {
		wait_jiffies = msecs_to_jiffies(dirty_writeback_interval * 10);
		schedule_timeout_interruptible(wait_jiffies);
		} else {
		set_current_state(TASK_INTERRUPTIBLE);
		if (list_empty_careful(&wb->bdi->work_list) &&
		!kthread_should_stop())
		schedule();
		if (!list_empty(&bdi->work_list)) {
		__set_current_state(TASK_RUNNING);
		continue;
		}

		if (dirty_writeback_interval) {
		wait_jiffies = msecs_to_jiffies(dirty_writeback_interval * 10);
		schedule_timeout(wait_jiffies);
		} else
		schedule();

		try_to_freeze();
		}