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bdi: make backing_dev_info->wb.dwork canceling stricter

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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: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@fb.com>
This commit is contained in:
Tejun Heo 2014-09-08 08:03:59 +09:00 committed by Jens Axboe
parent b68757341d
commit c0ea1c22bc
1 changed files with 2 additions and 13 deletions
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15
mm/backing-dev.c
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@ -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]);