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>
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1 changed files with 9 additions and 8 deletions
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@ -848,16 +848,17 @@ int bdi_writeback_thread(void *data)
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break;
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}
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set_current_state(TASK_INTERRUPTIBLE);
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if (!list_empty(&bdi->work_list)) {
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__set_current_state(TASK_RUNNING);
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continue;
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}
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if (dirty_writeback_interval) {
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wait_jiffies = msecs_to_jiffies(dirty_writeback_interval * 10);
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schedule_timeout_interruptible(wait_jiffies);
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} else {
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set_current_state(TASK_INTERRUPTIBLE);
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if (list_empty_careful(&wb->bdi->work_list) &&
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!kthread_should_stop())
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schedule();
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__set_current_state(TASK_RUNNING);
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}
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schedule_timeout(wait_jiffies);
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} else
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schedule();
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try_to_freeze();
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}
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