From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id C811CC77B71 for ; Tue, 25 Apr 2023 09:42:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231646AbjDYJmt (ORCPT ); Tue, 25 Apr 2023 05:42:49 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39866 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233672AbjDYJmr (ORCPT ); Tue, 25 Apr 2023 05:42:47 -0400 Received: from mga04.intel.com (mga04.intel.com [192.55.52.120]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D078C5BBA; Tue, 25 Apr 2023 02:42:46 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1682415766; x=1713951766; h=date:from:to:cc:subject:message-id:references: mime-version:content-transfer-encoding:in-reply-to; bh=bftSZwIs1nOeFyqVaNVBQT2KhTtuH2e3mtNCB3+bL3Q=; b=PjhhkZa5cGompLxX4aEGvM4a5gTH/922311z5yZkECU+knjeerOVzZHt lzdqeG6rba4YqvwGUda579wRpUPMPvTw1BAE2JDe3dRoKQw/PGHA33jcp /63ELTkZVmEakQbFPp+bbi7p2Uejx0IFbQ/Ao4Ju8SKLZUQC6HkfNhrNH I1saxONet5OqddXiHFivXipK/qQlla0Ufk8Rw4/V2PUxPEEBmZ1889oA7 v5HscHJnE5fLtx33kjHRafMCF7v8bHHjVCQA6E5skmPEgF6TjKpDEXEuR ZYFIn9ZAw9V4t1ezli+btQA/jDpLJ3nveMoCEdnd5dIcUjJ59WTX0Q2s9 Q==; X-IronPort-AV: E=McAfee;i="6600,9927,10690"; a="345468573" X-IronPort-AV: E=Sophos;i="5.99,225,1677571200"; d="scan'208";a="345468573" Received: from fmsmga002.fm.intel.com ([10.253.24.26]) by fmsmga104.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Apr 2023 02:42:46 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10690"; a="805014078" X-IronPort-AV: E=Sophos;i="5.99,225,1677571200"; d="scan'208";a="805014078" Received: from linux.bj.intel.com ([10.238.156.127]) by fmsmga002-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Apr 2023 02:42:44 -0700 Date: Tue, 25 Apr 2023 17:41:20 +0800 From: Tao Su To: Yu Kuai Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, tj@kernel.org, josef@toxicpanda.com, axboe@kernel.dk Subject: Re: [PATCH] Remove blkg node after destroying blkg Message-ID: References: <20230425075911.839539-1-tao1.su@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Tue, Apr 25, 2023 at 04:09:34PM +0800, Yu Kuai wrote: > Hi, > > 在 2023/04/25 15:59, Tao Su 写道: > > Kernel hang when poweroff or reboot, due to infinite restart in function > > blkg_destroy_all. It will goto restart label when a batch of blkgs are > > destroyed, but not remove blkg node in blkg_list. So the blkg_list is > > same in every 'restart' and result in kernel hang. > > > > By adding list_del to remove blkg node after destroying, can solve this > > kernel hang issue and satisfy the previous will to 'restart'. > > > > Reported-by: Xiangfei Ma > > Tested-by: Xiangfei Ma > > Tested-by: Farrah Chen > > Signed-off-by: Tao Su > > --- > > block/blk-cgroup.c | 1 + > > 1 file changed, 1 insertion(+) > > > > diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c > > index bd50b55bdb61..960eb538a704 100644 > > --- a/block/blk-cgroup.c > > +++ b/block/blk-cgroup.c > > @@ -530,6 +530,7 @@ static void blkg_destroy_all(struct gendisk *disk) > > spin_lock(&blkcg->lock); > > blkg_destroy(blkg); > > + list_del(&blkg->q_node); > > blkg should stay on the queue list until blkg_free_workfn(), otherwise > parent blkg can be freed before child, which will cause some known > issue. Yes, directly removing blkg node is not appropriate, which I noticed some comments in blkg_destroy(), thanks for pointing out this issue. > > I think this hung happens when total blkg is greater than > BLKG_DESTROY_BATCH_SIZE, right? Yes, you are right. > > Can you try if following patch fix your problem? This patch can also fix my problem, and indeed is a more secure way. Thanks, Tao > > index 1c1ebeb51003..0ecb4cce8af2 100644 > --- a/block/blk-cgroup.c > +++ b/block/blk-cgroup.c > @@ -527,6 +527,9 @@ static void blkg_destroy_all(struct gendisk *disk) > list_for_each_entry_safe(blkg, n, &q->blkg_list, q_node) { > struct blkcg *blkcg = blkg->blkcg; > > + if (hlist_unhashed(&blkg->blkcg_node)) > + continue; > + > spin_lock(&blkcg->lock); > blkg_destroy(blkg); > spin_unlock(&blkcg->lock); > > > spin_unlock(&blkcg->lock); > > /* > >