bcache: release dc->writeback_lock properly in bch_writeback_thread()

The writeback thread would exit with a lock held when the cache device
is detached via sysfs interface, fix it by releasing the held lock
before exiting the while-loop.

Fixes: fadd94e05c02 (bcache: quit dc->writeback_thread when BCACHE_DEV_DETACHING is set)
Signed-off-by: Shan Hai <shan.hai@oracle.com>
Signed-off-by: Coly Li <colyli@suse.de>
Tested-by: Shenghui Wang <shhuiw@foxmail.com>
Cc: stable@vger.kernel.org #4.17+
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/drivers/md/bcache/writeback.c b/drivers/md/bcache/writeback.c
index 6be05bd7ca6711637ac04b57bc5c244caaa95f4b..08c3a9f9676c9e89649b56f765fb378973149a62 100644 (file)
--- a/drivers/md/bcache/writeback.c
+++ b/drivers/md/bcache/writeback.c
@@ -685,8 +685,10 @@ static int bch_writeback_thread(void *arg)
                         * data on cache. BCACHE_DEV_DETACHING flag is set in
                         * bch_cached_dev_detach().
                         */
-                       if (test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags))
+                       if (test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags)) {
+                               up_write(&dc->writeback_lock);
                                break;
+                       }
                }
 
                up_write(&dc->writeback_lock);