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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>
This commit is contained in:
Artem Bityutskiy 2010-07-25 14:29:15 +03:00 committed by Jens Axboe
parent c4ec7908c2
commit 297252c81d
1 changed files with 9 additions and 8 deletions
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17
fs/fs-writeback.c
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@ -848,16 +848,17 @@ int bdi_writeback_thread(void *data)
break;
}
set_current_state(TASK_INTERRUPTIBLE);
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_interruptible(wait_jiffies);
} else {
set_current_state(TASK_INTERRUPTIBLE);
if (list_empty_careful(&wb->bdi->work_list) &&
!kthread_should_stop())
schedule();
__set_current_state(TASK_RUNNING);
}
schedule_timeout(wait_jiffies);
} else
schedule();
try_to_freeze();
}