From: Tang Junhui <tang.junhui@xxxxxxxxxx> Hello Coly, >When cache set is stopping, calculating writeback rate is wast of time. >This is the purpose of the first checking, to avoid unnecessary delay >from bcache_flash_devs_sectors_dirty() inside __update_writeback_rate(). I thought twice, and found there is still a race. work update_writeback_rate is runing: >@@ -91,6 +91,11 @@ static void update_writeback_rate(struct work_struct *work) > struct cached_dev *dc = container_of(to_delayed_work(work), > struct cached_dev, > writeback_rate_update); >+ struct cache_set *c = dc->disk.c; >+ >+ /* quit directly if cache set is stopping */ >+ if (test_bit(CACHE_SET_STOPPING, &c->flags)) >+ return; > > down_read(&dc->writeback_lock); > >@@ -100,6 +105,10 @@ static void update_writeback_rate(struct work_struct *work) > > up_read(&dc->writeback_lock); > >+ /* do not schedule delayed work if cache set is stopping */ >+ if (test_bit(CACHE_SET_STOPPING, &c->flags)) >+ return; >+ and if cancel_delayed_wsrksync() runs at this moment, the code can not prevent the work re-arming itself to workqueue. So maybe we need a locker to protect it. > schedule_delayed_work(&dc->writeback_rate_update, > dc->writeback_rate_update_seconds * HZ); > } Thanks, Tang Junhui
