From: Shenghui Wang Date: Thu, 13 Dec 2018 14:53:50 +0000 (+0800) Subject: bcache: do not mark writeback_running too early X-Git-Tag: v4.19.88~227 X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=b2d84967f07658bab63e6157bd2758db5cc68c86;p=thirdparty%2Fkernel%2Fstable.git bcache: do not mark writeback_running too early [ Upstream commit 79b791466e525c98f6aeee9acf5726e7b27f4231 ] A fresh backing device is not attached to any cache_set, and has no writeback kthread created until first attached to some cache_set. But bch_cached_dev_writeback_init run " dc->writeback_running = true; WARN_ON(test_and_clear_bit(BCACHE_DEV_WB_RUNNING, &dc->disk.flags)); " for any newly formatted backing devices. For a fresh standalone backing device, we can get something like following even if no writeback kthread created: ------------------------ /sys/block/bcache0/bcache# cat writeback_running 1 /sys/block/bcache0/bcache# cat writeback_rate_debug rate: 512.0k/sec dirty: 0.0k target: 0.0k proportional: 0.0k integral: 0.0k change: 0.0k/sec next io: -15427384ms The none ZERO fields are misleading as no alive writeback kthread yet. Set dc->writeback_running false as no writeback thread created in bch_cached_dev_writeback_init(). We have writeback thread created and woken up in bch_cached_dev_writeback _start(). Set dc->writeback_running true before bch_writeback_queue() called, as a writeback thread will check if dc->writeback_running is true before writing back dirty data, and hung if false detected. After the change, we can get the following output for a fresh standalone backing device: ----------------------- /sys/block/bcache0/bcache$ cat writeback_running 0 /sys/block/bcache0/bcache# cat writeback_rate_debug rate: 0.0k/sec dirty: 0.0k target: 0.0k proportional: 0.0k integral: 0.0k change: 0.0k/sec next io: 0ms v1 -> v2: Set dc->writeback_running before bch_writeback_queue() called, Signed-off-by: Shenghui Wang Signed-off-by: Coly Li Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin --- diff --git a/drivers/md/bcache/writeback.c b/drivers/md/bcache/writeback.c index ba5395fd386d5..b5fc3c6c7178e 100644 --- a/drivers/md/bcache/writeback.c +++ b/drivers/md/bcache/writeback.c @@ -781,7 +781,7 @@ void bch_cached_dev_writeback_init(struct cached_dev *dc) bch_keybuf_init(&dc->writeback_keys); dc->writeback_metadata = true; - dc->writeback_running = true; + dc->writeback_running = false; dc->writeback_percent = 10; dc->writeback_delay = 30; atomic_long_set(&dc->writeback_rate.rate, 1024); @@ -810,6 +810,7 @@ int bch_cached_dev_writeback_start(struct cached_dev *dc) destroy_workqueue(dc->writeback_write_wq); return PTR_ERR(dc->writeback_thread); } + dc->writeback_running = true; WARN_ON(test_and_set_bit(BCACHE_DEV_WB_RUNNING, &dc->disk.flags)); schedule_delayed_work(&dc->writeback_rate_update,