From patchwork Sat Jan 27 14:23:57 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Coly Li X-Patchwork-Id: 10187537 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id DFC9D60383 for ; Sat, 27 Jan 2018 15:03:07 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id D5EF3228C8 for ; Sat, 27 Jan 2018 15:03:07 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id CA2CF28138; Sat, 27 Jan 2018 15:03:07 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 311F8228C8 for ; Sat, 27 Jan 2018 15:03:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752947AbeA0PDG (ORCPT ); Sat, 27 Jan 2018 10:03:06 -0500 Received: from mx2.suse.de ([195.135.220.15]:37593 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751626AbeA0PDF (ORCPT ); Sat, 27 Jan 2018 10:03:05 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (charybdis-ext.suse.de [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id 84E70AE8C; Sat, 27 Jan 2018 14:59:23 +0000 (UTC) From: Coly Li To: linux-bcache@vger.kernel.org Cc: linux-block@vger.kernel.org, Coly Li , Michael Lyle , Hannes Reinecke , Huijun Tang Subject: [PATCH v4 04/13] bcache: quit dc->writeback_thread when BCACHE_DEV_DETACHING is set Date: Sat, 27 Jan 2018 22:23:57 +0800 Message-Id: <20180127142406.89741-5-colyli@suse.de> X-Mailer: git-send-email 2.15.1 In-Reply-To: <20180127142406.89741-1-colyli@suse.de> References: <20180127142406.89741-1-colyli@suse.de> Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP In patch "bcache: fix cached_dev->count usage for bch_cache_set_error()", cached_dev_get() is called when creating dc->writeback_thread, and cached_dev_put() is called when exiting dc->writeback_thread. This modification works well unless people detach the bcache device manually by 'echo 1 > /sys/block/bcache/bcache/detach' Because this sysfs interface only calls bch_cached_dev_detach() which wakes up dc->writeback_thread but does not stop it. The reason is, before patch "bcache: fix cached_dev->count usage for bch_cache_set_error()", inside bch_writeback_thread(), if cache is not dirty after writeback, cached_dev_put() will be called here. And in cached_dev_make_request() when a new write request makes cache from clean to dirty, cached_dev_get() will be called there. Since we don't operate dc->count in these locations, refcount d->count cannot be dropped after cache becomes clean, and cached_dev_detach_finish() won't be called to detach bcache device. This patch fixes the issue by checking whether BCACHE_DEV_DETACHING is set inside bch_writeback_thread(). If this bit is set and cache is clean (no existing writeback_keys), break the while-loop, call cached_dev_put() and quit the writeback thread. Please note if cache is still dirty, even BCACHE_DEV_DETACHING is set the writeback thread should continue to perform writeback, this is the original design of manually detach. I compose a separte patch because that patch "bcache: fix cached_dev->count usage for bch_cache_set_error()" already gets a "Reviewed-by:" from Hannes Reinecke. Also this fix is not trivial and good for a separate patch. Signed-off-by: Coly Li Cc: Michael Lyle Cc: Hannes Reinecke Cc: Huijun Tang --- drivers/md/bcache/writeback.c | 20 +++++++++++++++++--- 1 file changed, 17 insertions(+), 3 deletions(-) diff --git a/drivers/md/bcache/writeback.c b/drivers/md/bcache/writeback.c index b280c134dd4d..4dbeaaa575bf 100644 --- a/drivers/md/bcache/writeback.c +++ b/drivers/md/bcache/writeback.c @@ -565,9 +565,15 @@ static int bch_writeback_thread(void *arg) while (!kthread_should_stop()) { down_write(&dc->writeback_lock); set_current_state(TASK_INTERRUPTIBLE); - if (!atomic_read(&dc->has_dirty) || - (!test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags) && - !dc->writeback_running)) { + /* + * If the bache device is detaching, skip here and continue + * to perform writeback. Otherwise, if no dirty data on cache, + * or there is dirty data on cache but writeback is disabled, + * the writeback thread should sleep here and wait for others + * to wake up it. + */ + if (!test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags) && + (!atomic_read(&dc->has_dirty) || !dc->writeback_running)) { up_write(&dc->writeback_lock); if (kthread_should_stop()) { @@ -587,6 +593,14 @@ static int bch_writeback_thread(void *arg) atomic_set(&dc->has_dirty, 0); SET_BDEV_STATE(&dc->sb, BDEV_STATE_CLEAN); bch_write_bdev_super(dc, NULL); + /* + * If bcache device is detaching via sysfs interface, + * writeback thread should stop after there is no dirty + * data on cache. BCACHE_DEV_DETACHING flag is set in + * bch_cached_dev_detach(). + */ + if (test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags)) + break; } up_write(&dc->writeback_lock);