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Commit c0ea1c22 authored by Tejun Heo's avatar Tejun Heo Committed by Jens Axboe
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bdi: make backing_dev_info->wb.dwork canceling stricter 



Canceling of bdi->wb.dwork is currently a bit mushy.
bdi_wb_shutdown() performs cancel_delayed_work_sync() at the end after
shutting down and flushing the delayed_work and bdi_destroy() tries
yet again after bdi_unregister().

bdi->wb.dwork is queued only after checking BDI_registered while
holding bdi->wb_lock and bdi_wb_shutdown() clears the flag while
holding the same lock and then flushes the delayed_work.  There's no
way the delayed_work can be queued again after that.

Replace the two unnecessary cancel_delayed_work_sync() invocations
with WARNs on pending.  This simplifies and clarifies the code a bit
and will help future changes in further isolating bdi_writeback
handling.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Signed-off-by: default avatarJens Axboe <axboe@fb.com>
parent b6875734

mm/backing-dev.c

+2 −13
Original line number Diff line number Diff line
@@ -376,13 +376,7 @@ static void bdi_wb_shutdown(struct backing_dev_info *bdi) 
	mod_delayed_work(bdi_wq, &bdi->wb.dwork, 0);

	flush_delayed_work(&bdi->wb.dwork);

	WARN_ON(!list_empty(&bdi->work_list));



	/*

	 * This shouldn't be necessary unless @bdi for some reason has

	 * unflushed dirty IO after work_list is drained.  Do it anyway

	 * just in case.

	 */

	cancel_delayed_work_sync(&bdi->wb.dwork);

	WARN_ON(delayed_work_pending(&bdi->wb.dwork));

}



/*
@@ -497,12 +491,7 @@ void bdi_destroy(struct backing_dev_info *bdi) 


	bdi_unregister(bdi);



	/*

	 * If bdi_unregister() had already been called earlier, the dwork

	 * could still be pending because bdi_prune_sb() can race with the

	 * bdi_wakeup_thread_delayed() calls from __mark_inode_dirty().

	 */

	cancel_delayed_work_sync(&bdi->wb.dwork);

	WARN_ON(delayed_work_pending(&bdi->wb.dwork));



	for (i = 0; i < NR_BDI_STAT_ITEMS; i++)

		percpu_counter_destroy(&bdi->bdi_stat[i]);