Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932567AbcDBAz6 (ORCPT ); Fri, 1 Apr 2016 20:55:58 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:54160 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932469AbcDBAzx (ORCPT ); Fri, 1 Apr 2016 20:55:53 -0400 From: Kamal Mostafa To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: Eric Wheeler , Jens Axboe , Kamal Mostafa Subject: [PATCH 3.19.y-ckt 071/170] bcache: fix race of writeback thread starting before complete initialization Date: Fri, 1 Apr 2016 17:52:37 -0700 Message-Id: <1459558456-24452-72-git-send-email-kamal@canonical.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1459558456-24452-1-git-send-email-kamal@canonical.com> References: <1459558456-24452-1-git-send-email-kamal@canonical.com> X-Extended-Stable: 3.19 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1905 Lines: 55 3.19.8-ckt18 -stable review patch. If anyone has any objections, please let me know. ---8<------------------------------------------------------------ From: Eric Wheeler commit 07cc6ef8edc47f8b4fc1e276d31127a0a5863d4d upstream. The bch_writeback_thread might BUG_ON in read_dirty() if dc->sb==BDEV_STATE_DIRTY and bch_sectors_dirty_init has not yet completed its related initialization. This patch downs the dc->writeback_lock until after initialization is complete, thus preventing bch_writeback_thread from proceeding prematurely. See this thread: http://thread.gmane.org/gmane.linux.kernel.bcache.devel/3453 Signed-off-by: Eric Wheeler Tested-by: Marc MERLIN Signed-off-by: Jens Axboe Signed-off-by: Kamal Mostafa --- drivers/md/bcache/super.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c index 42522c8..e83629a 100644 --- a/drivers/md/bcache/super.c +++ b/drivers/md/bcache/super.c @@ -1046,8 +1046,12 @@ int bch_cached_dev_attach(struct cached_dev *dc, struct cache_set *c) */ atomic_set(&dc->count, 1); - if (bch_cached_dev_writeback_start(dc)) + /* Block writeback thread, but spawn it */ + down_write(&dc->writeback_lock); + if (bch_cached_dev_writeback_start(dc)) { + up_write(&dc->writeback_lock); return -ENOMEM; + } if (BDEV_STATE(&dc->sb) == BDEV_STATE_DIRTY) { bch_sectors_dirty_init(dc); @@ -1059,6 +1063,9 @@ int bch_cached_dev_attach(struct cached_dev *dc, struct cache_set *c) bch_cached_dev_run(dc); bcache_device_link(&dc->disk, c, "bdev"); + /* Allow the writeback thread to proceed */ + up_write(&dc->writeback_lock); + pr_info("Caching %s as %s on set %pU", bdevname(dc->bdev, buf), dc->disk.disk->disk_name, dc->disk.c->sb.set_uuid); -- 2.7.4