From patchwork Tue Feb 27 16:55:57 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Coly Li X-Patchwork-Id: 10245823 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 E458960384 for ; Tue, 27 Feb 2018 16:57:18 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id D4C6C289F9 for ; Tue, 27 Feb 2018 16:57:18 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id C9841289FB; Tue, 27 Feb 2018 16:57:18 +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 2D927289F9 for ; Tue, 27 Feb 2018 16:57:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751908AbeB0Q5R (ORCPT ); Tue, 27 Feb 2018 11:57:17 -0500 Received: from mx2.suse.de ([195.135.220.15]:47018 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751838AbeB0Q5Q (ORCPT ); Tue, 27 Feb 2018 11:57:16 -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 602D3AB38; Tue, 27 Feb 2018 16:57:15 +0000 (UTC) From: Coly Li To: linux-bcache@vger.kernel.org Cc: linux-block@vger.kernel.org, Coly Li , Michael Lyle , Junhui Tang Subject: [PATCH v7 9/9] bcache: stop bcache device when backing device is offline Date: Wed, 28 Feb 2018 00:55:57 +0800 Message-Id: <20180227165557.20442-10-colyli@suse.de> X-Mailer: git-send-email 2.16.1 In-Reply-To: <20180227165557.20442-1-colyli@suse.de> References: <20180227165557.20442-1-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 Currently bcache does not handle backing device failure, if backing device is offline and disconnected from system, its bcache device can still be accessible. If the bcache device is in writeback mode, I/O requests even can success if the requests hit on cache device. That is to say, when and how bcache handles offline backing device is undefined. This patch tries to handle backing device offline in a rather simple way, - Add cached_dev->status_update_thread kernel thread to update backing device status in every 1 second. - Add cached_dev->offline_seconds to record how many seconds the backing device is observed to be offline. If the backing device is offline for BACKING_DEV_OFFLINE_TIMEOUT (30) seconds, set dc->io_disable to 1 and call bcache_device_stop() to stop the bache device which linked to the offline backing device. Now if a backing device is offline for BACKING_DEV_OFFLINE_TIMEOUT seconds, its bcache device will be removed, then user space application writing on it will get error immediately, and handler the device failure in time. This patch is quite simple, does not handle more complicated situations. Once the bcache device is stopped, users need to recovery the backing device, register and attach it manually. Changelog: v3: call wait_for_kthread_stop() before exits kernel thread. v2: remove "bcache: " prefix when calling pr_warn(). v1: initial version. Signed-off-by: Coly Li Reviewed-by: Hannes Reinecke Cc: Michael Lyle Cc: Junhui Tang --- drivers/md/bcache/bcache.h | 2 ++ drivers/md/bcache/super.c | 55 ++++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 57 insertions(+) diff --git a/drivers/md/bcache/bcache.h b/drivers/md/bcache/bcache.h index d338b7086013..1cfe37dba0f1 100644 --- a/drivers/md/bcache/bcache.h +++ b/drivers/md/bcache/bcache.h @@ -345,6 +345,7 @@ struct cached_dev { struct keybuf writeback_keys; + struct task_struct *status_update_thread; /* * Order the write-half of writeback operations strongly in dispatch * order. (Maintain LBA order; don't allow reads completing out of @@ -392,6 +393,7 @@ struct cached_dev { #define DEFAULT_CACHED_DEV_ERROR_LIMIT 64 atomic_t io_errors; unsigned error_limit; + unsigned offline_seconds; }; enum alloc_reserve { diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c index cae4caac17da..abeb52bd9ebe 100644 --- a/drivers/md/bcache/super.c +++ b/drivers/md/bcache/super.c @@ -654,6 +654,11 @@ static int ioctl_dev(struct block_device *b, fmode_t mode, unsigned int cmd, unsigned long arg) { struct bcache_device *d = b->bd_disk->private_data; + struct cached_dev *dc = container_of(d, struct cached_dev, disk); + + if (dc->io_disable) + return -EIO; + return d->ioctl(d, mode, cmd, arg); } @@ -864,6 +869,45 @@ static void calc_cached_dev_sectors(struct cache_set *c) c->cached_dev_sectors = sectors; } +#define BACKING_DEV_OFFLINE_TIMEOUT 5 +static int cached_dev_status_update(void *arg) +{ + struct cached_dev *dc = arg; + struct request_queue *q; + char buf[BDEVNAME_SIZE]; + + /* + * If this delayed worker is stopping outside, directly quit here. + * dc->io_disable might be set via sysfs interface, so check it + * here too. + */ + while (!kthread_should_stop() && !dc->io_disable) { + q = bdev_get_queue(dc->bdev); + if (blk_queue_dying(q)) + dc->offline_seconds++; + else + dc->offline_seconds = 0; + + if (dc->offline_seconds >= BACKING_DEV_OFFLINE_TIMEOUT) { + pr_err("%s: device offline for %d seconds", + bdevname(dc->bdev, buf), + BACKING_DEV_OFFLINE_TIMEOUT); + pr_err("%s: disable I/O request due to backing " + "device offline", dc->disk.name); + dc->io_disable = true; + /* let others know earlier that io_disable is true */ + smp_mb(); + bcache_device_stop(&dc->disk); + break; + } + + schedule_timeout_interruptible(HZ); + } + + wait_for_kthread_stop(); + return 0; +} + void bch_cached_dev_run(struct cached_dev *dc) { struct bcache_device *d = &dc->disk; @@ -906,6 +950,15 @@ void bch_cached_dev_run(struct cached_dev *dc) if (sysfs_create_link(&d->kobj, &disk_to_dev(d->disk)->kobj, "dev") || sysfs_create_link(&disk_to_dev(d->disk)->kobj, &d->kobj, "bcache")) pr_debug("error creating sysfs link"); + + dc->status_update_thread = kthread_run(cached_dev_status_update, + dc, + "bcache_status_update"); + if (IS_ERR(dc->status_update_thread)) { + pr_warn("failed to create bcache_status_update kthread, " + "continue to run without monitoring backing " + "device status"); + } } /* @@ -1128,6 +1181,8 @@ static void cached_dev_free(struct closure *cl) kthread_stop(dc->writeback_thread); if (dc->writeback_write_wq) destroy_workqueue(dc->writeback_write_wq); + if (!IS_ERR_OR_NULL(dc->status_update_thread)) + kthread_stop(dc->status_update_thread); if (atomic_read(&dc->running)) bd_unlink_disk_holder(dc->bdev, dc->disk.disk);