From patchwork Thu Apr 26 19:23:49 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jeff Mahoney X-Patchwork-Id: 10366715 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 DDDD06032C for ; Thu, 26 Apr 2018 19:24:16 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id CDE1529218 for ; Thu, 26 Apr 2018 19:24:16 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id CB8AA29235; Thu, 26 Apr 2018 19:24:16 +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=-7.9 required=2.0 tests=BAYES_00, MAILING_LIST_MULTI, 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 13FF429226 for ; Thu, 26 Apr 2018 19:24:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753498AbeDZTX6 (ORCPT ); Thu, 26 Apr 2018 15:23:58 -0400 Received: from mx2.suse.de ([195.135.220.15]:39408 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752754AbeDZTX4 (ORCPT ); Thu, 26 Apr 2018 15:23:56 -0400 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 537FFACC0 for ; Thu, 26 Apr 2018 19:23:55 +0000 (UTC) Received: from sled4.home.jeffm.io (sled4.home.jeffm.io [192.168.111.8]) by mail.home.jeffm.io (Postfix) with ESMTPS id 55DAD81AD3C1; Thu, 26 Apr 2018 15:23:34 -0400 (EDT) Received: by sled4.home.jeffm.io (Postfix, from userid 1000) id 466B53F48; Thu, 26 Apr 2018 15:23:52 -0400 (EDT) From: jeffm@suse.com To: linux-btrfs@vger.kernel.org Cc: Jeff Mahoney Subject: [PATCH 1/3] btrfs: qgroups, fix rescan worker running races Date: Thu, 26 Apr 2018 15:23:49 -0400 Message-Id: <20180426192351.473-1-jeffm@suse.com> X-Mailer: git-send-email 2.12.3 Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP From: Jeff Mahoney Commit d2c609b834d6 (Btrfs: fix qgroup rescan worker initialization) fixed the issue with BTRFS_IOC_QUOTA_RESCAN_WAIT being racy, but ended up reintroducing the hang-on-unmount bug that the commit it intended to fix addressed. The race this time is between qgroup_rescan_init setting ->qgroup_rescan_running = true and the worker starting. There are many scenarios where we initialize the worker and never start it. The completion btrfs_ioctl_quota_rescan_wait waits for will never come. This can happen even without involving error handling, since mounting the file system read-only returns between initializing the worker and queueing it. The right place to do it is when we're queuing the worker. The flag really just means that btrfs_ioctl_quota_rescan_wait should wait for a completion. This patch introduces a new helper, queue_rescan_worker, that handles the ->qgroup_rescan_running flag, including any races with umount. While we're at it, ->qgroup_rescan_running is protected only by the ->qgroup_rescan_mutex. btrfs_ioctl_quota_rescan_wait doesn't need to take the spinlock too. Fixes: d2c609b834d6 (Btrfs: fix qgroup rescan worker initialization) Signed-off-by: Jeff Mahoney Reviewed-by: Nikolay Borisov --- fs/btrfs/ctree.h | 1 + fs/btrfs/qgroup.c | 40 ++++++++++++++++++++++++++++------------ 2 files changed, 29 insertions(+), 12 deletions(-) diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h index da308774b8a4..dbba615f4d0f 100644 --- a/fs/btrfs/ctree.h +++ b/fs/btrfs/ctree.h @@ -1045,6 +1045,7 @@ struct btrfs_fs_info { struct btrfs_workqueue *qgroup_rescan_workers; struct completion qgroup_rescan_completion; struct btrfs_work qgroup_rescan_work; + /* qgroup rescan worker is running or queued to run */ bool qgroup_rescan_running; /* protected by qgroup_rescan_lock */ /* filesystem state */ diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c index aa259d6986e1..be491b6c020a 100644 --- a/fs/btrfs/qgroup.c +++ b/fs/btrfs/qgroup.c @@ -2072,6 +2072,30 @@ int btrfs_qgroup_account_extents(struct btrfs_trans_handle *trans, return ret; } +static void queue_rescan_worker(struct btrfs_fs_info *fs_info) +{ + mutex_lock(&fs_info->qgroup_rescan_lock); + if (btrfs_fs_closing(fs_info)) { + mutex_unlock(&fs_info->qgroup_rescan_lock); + return; + } + if (WARN_ON(fs_info->qgroup_rescan_running)) { + btrfs_warn(fs_info, "rescan worker already queued"); + mutex_unlock(&fs_info->qgroup_rescan_lock); + return; + } + + /* + * Being queued is enough for btrfs_qgroup_wait_for_completion + * to need to wait. + */ + fs_info->qgroup_rescan_running = true; + mutex_unlock(&fs_info->qgroup_rescan_lock); + + btrfs_queue_work(fs_info->qgroup_rescan_workers, + &fs_info->qgroup_rescan_work); +} + /* * called from commit_transaction. Writes all changed qgroups to disk. */ @@ -2123,8 +2147,7 @@ int btrfs_run_qgroups(struct btrfs_trans_handle *trans, ret = qgroup_rescan_init(fs_info, 0, 1); if (!ret) { qgroup_rescan_zero_tracking(fs_info); - btrfs_queue_work(fs_info->qgroup_rescan_workers, - &fs_info->qgroup_rescan_work); + queue_rescan_worker(fs_info); } ret = 0; } @@ -2713,7 +2736,6 @@ qgroup_rescan_init(struct btrfs_fs_info *fs_info, u64 progress_objectid, sizeof(fs_info->qgroup_rescan_progress)); fs_info->qgroup_rescan_progress.objectid = progress_objectid; init_completion(&fs_info->qgroup_rescan_completion); - fs_info->qgroup_rescan_running = true; spin_unlock(&fs_info->qgroup_lock); mutex_unlock(&fs_info->qgroup_rescan_lock); @@ -2785,9 +2807,7 @@ btrfs_qgroup_rescan(struct btrfs_fs_info *fs_info) qgroup_rescan_zero_tracking(fs_info); - btrfs_queue_work(fs_info->qgroup_rescan_workers, - &fs_info->qgroup_rescan_work); - + queue_rescan_worker(fs_info); return 0; } @@ -2798,9 +2818,7 @@ int btrfs_qgroup_wait_for_completion(struct btrfs_fs_info *fs_info, int ret = 0; mutex_lock(&fs_info->qgroup_rescan_lock); - spin_lock(&fs_info->qgroup_lock); running = fs_info->qgroup_rescan_running; - spin_unlock(&fs_info->qgroup_lock); mutex_unlock(&fs_info->qgroup_rescan_lock); if (!running) @@ -2819,12 +2837,10 @@ int btrfs_qgroup_wait_for_completion(struct btrfs_fs_info *fs_info, * this is only called from open_ctree where we're still single threaded, thus * locking is omitted here. */ -void -btrfs_qgroup_rescan_resume(struct btrfs_fs_info *fs_info) +void btrfs_qgroup_rescan_resume(struct btrfs_fs_info *fs_info) { if (fs_info->qgroup_flags & BTRFS_QGROUP_STATUS_FLAG_RESCAN) - btrfs_queue_work(fs_info->qgroup_rescan_workers, - &fs_info->qgroup_rescan_work); + queue_rescan_worker(fs_info); } /*