79b791466e
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 <shhuiw@foxmail.com> Signed-off-by: Coly Li <colyli@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.