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 X-Spam-Level: X-Spam-Status: No, score=-8.3 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C8EFCC10DCE for ; Fri, 6 Mar 2020 14:00:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9BAC420848 for ; Fri, 6 Mar 2020 14:00:35 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="ZhFOhSck" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726833AbgCFOAe (ORCPT ); Fri, 6 Mar 2020 09:00:34 -0500 Received: from mail-pl1-f193.google.com ([209.85.214.193]:33075 "EHLO mail-pl1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726490AbgCFOAe (ORCPT ); Fri, 6 Mar 2020 09:00:34 -0500 Received: by mail-pl1-f193.google.com with SMTP id ay11so913427plb.0; Fri, 06 Mar 2020 06:00:33 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:date:to:cc:subject:message-id:references:mime-version :content-disposition:content-transfer-encoding:in-reply-to :user-agent; bh=efYr67/bTkt21SGtVdNVaerWisMPAYyt0fWiDVwgGjk=; b=ZhFOhSckcSX8pV1bWCS4o4akz+nRynoamY/zQbaiHWh4a4IFicLY2Jk2OA1ffM/i96 eKSC7h1EHCAaBCWypKBn5baMCTGxLnvA0ZoRF5qH3MVCUygz0pvYc4ujRChBBC2winPL saqJr4tzjm/7nPA7h/3U6NFw+J6EpK7EEKiQqDwhlRq68FbeHpxlOvw/xT1YlLaN4TPv P4F4KzqovD9pMu1zybSbESrlfUsJ7i1jt2NP7+iRv8sLn0VesWDFwofj1m1tPw2Us7SQ NVJE1uLk/ZZM8/7mH2Gdz/DybhRTFl0UmO/yWNOtoz0NGRC0QMsV0di74laEg8OwmWBw 2/5Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:date:to:cc:subject:message-id:references :mime-version:content-disposition:content-transfer-encoding :in-reply-to:user-agent; bh=efYr67/bTkt21SGtVdNVaerWisMPAYyt0fWiDVwgGjk=; b=H5S1hDzZ1NZxCal+L06G1r/j2bBcoTG4rQ5eUuiFY4UaifIFQ7BM4yLzwZ0/R9Lxgj zhl5CARQh+DEddu2ljGufjy/EXgZLsC6NOqExRt3xniKIY6Y5NUpZEvbK8u1fPORsQEv RI02yD+D0ZNveOqILP/L35/3yg20uqTnGaxkwjfZ0s2VnWoMowLW5onVtfFQ9Z3oEw1r hFLWrQvnPhb3DzROG0S3aVRHtCBB8dfxVaovAgUAQ1tyxr32ZBf7Q6K98CyS10kRICJf 8pWAlBM65JR84C2mHnthSBoQqYMtwkKbMXCGn6UWIOU+A3PCueFOhtZyCCZ575j0ctJ9 gDww== X-Gm-Message-State: ANhLgQ0P9M2+awHF/FDPmkEdRJDmJHOzNnwGNd+93tsPix3PT84B5ID6 SBAYjdHfE3spmSiKaIZfXw== X-Google-Smtp-Source: ADFU+vtNUgRRJn2bRpQQmczbG/BE5no1t/hK7c/TWORsRGmvhtlbbtZao22ZUYqyVEVeSlNkEM5WOw== X-Received: by 2002:a17:90a:3701:: with SMTP id u1mr3681744pjb.25.1583503233154; Fri, 06 Mar 2020 06:00:33 -0800 (PST) Received: from madhuparna-HP-Notebook ([218.248.46.83]) by smtp.gmail.com with ESMTPSA id g11sm7631037pfo.184.2020.03.06.06.00.28 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Fri, 06 Mar 2020 06:00:31 -0800 (PST) From: Madhuparna Bhowmik X-Google-Original-From: Madhuparna Bhowmik Date: Fri, 6 Mar 2020 19:30:24 +0530 To: Qu Wenruo Cc: madhuparnabhowmik10@gmail.com, clm@fb.com, josef@toxicpanda.com, dsterba@suse.com, linux-btrfs@vger.kernel.org, linux-kernel@vger.kernel.org, joel@joelfernandes.org, linux-kernel-mentees@lists.linuxfoundation.org, paulmck@kernel.org, frextrite@gmail.com, linux@roeck-us.net Subject: Re: [PATCH] fs: btrfs: block-group.c: Fix suspicious RCU usage warning Message-ID: <20200306140023.GA14186@madhuparna-HP-Notebook> References: <20200306065243.11699-1-madhuparnabhowmik10@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Mar 06, 2020 at 03:16:53PM +0800, Qu Wenruo wrote: > > > On 2020/3/6 下午2:52, madhuparnabhowmik10@gmail.com wrote: > > From: Madhuparna Bhowmik > > > > The space_info list is rcu protected. > > Hence, it should be traversed with rcu_read_lock held. > > > > Warning: > > [ 29.104591] ============================= > > [ 29.104756] WARNING: suspicious RCU usage > > [ 29.105046] 5.6.0-rc4-next-20200305 #1 Not tainted > > [ 29.105231] ----------------------------- > > [ 29.105401] fs/btrfs/block-group.c:2011 RCU-list traversed in non-reader section!! > > > > Reported-by: Guenter Roeck > > Signed-off-by: Madhuparna Bhowmik > > --- > > fs/btrfs/block-group.c | 4 +++- > > 1 file changed, 3 insertions(+), 1 deletion(-) > > > > diff --git a/fs/btrfs/block-group.c b/fs/btrfs/block-group.c > > index 404e050ce8ee..9cabeef66f5b 100644 > > --- a/fs/btrfs/block-group.c > > +++ b/fs/btrfs/block-group.c > > @@ -1987,6 +1987,7 @@ int btrfs_read_block_groups(struct btrfs_fs_info *info) > > This function is only triggered at mount time, where no other rcu > operation can happen. > Thanks Qu. Joel and Paul, what should we do in this case? Should we just pass cond = true or use list_for_each_entry instead? Thank you, Madhuparna > Thanks, > Qu > > btrfs_release_path(path); > > } > > > > + rcu_read_lock(); > > list_for_each_entry_rcu(space_info, &info->space_info, list) { > > if (!(btrfs_get_alloc_profile(info, space_info->flags) & > > (BTRFS_BLOCK_GROUP_RAID10 | > > @@ -2007,7 +2008,8 @@ int btrfs_read_block_groups(struct btrfs_fs_info *info) > > list) > > inc_block_group_ro(cache, 1); > > } > > - > > + rcu_read_unlock(); > > + > > btrfs_init_global_block_rsv(info); > > ret = check_chunk_block_group_mappings(info); > > error: > > >