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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=unavailable 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 049A2C43603 for ; Fri, 13 Dec 2019 21:07:48 +0000 (UTC) Received: from fraxinus.osuosl.org (smtp4.osuosl.org [140.211.166.137]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 4D71A24671 for ; Fri, 13 Dec 2019 21:07:47 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4D71A24671 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.cz Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linux-kernel-mentees-bounces@lists.linuxfoundation.org Received: from localhost (localhost [127.0.0.1]) by fraxinus.osuosl.org (Postfix) with ESMTP id 2B133873B0; Fri, 13 Dec 2019 19:49:52 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from fraxinus.osuosl.org ([127.0.0.1]) by localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id FpspJDPDGVI6; Fri, 13 Dec 2019 19:49:51 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [140.211.9.56]) by fraxinus.osuosl.org (Postfix) with ESMTP id 642D1873AB; Fri, 13 Dec 2019 19:49:51 +0000 (UTC) Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id 52707C1D7C; Fri, 13 Dec 2019 19:49:51 +0000 (UTC) Received: from hemlock.osuosl.org (smtp2.osuosl.org [140.211.166.133]) by lists.linuxfoundation.org (Postfix) with ESMTP id 40BFAC0881 for ; Fri, 13 Dec 2019 19:49:49 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by hemlock.osuosl.org (Postfix) with ESMTP id 2C8A7888E2 for ; Fri, 13 Dec 2019 19:49:49 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from hemlock.osuosl.org ([127.0.0.1]) by localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 9sMReVsA9jc2 for ; Fri, 13 Dec 2019 19:49:47 +0000 (UTC) X-Greylist: domain auto-whitelisted by SQLgrey-1.7.6 Received: from mx1.suse.de (mx2.suse.de [195.135.220.15]) by hemlock.osuosl.org (Postfix) with ESMTPS id 19764888DC for ; Fri, 13 Dec 2019 19:49:46 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 76B8EAF65; Fri, 13 Dec 2019 19:49:44 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id 36FA41E0609; Fri, 13 Dec 2019 20:49:43 +0100 (CET) Date: Fri, 13 Dec 2019 20:49:43 +0100 From: Jan Kara To: Joel Fernandes Message-ID: <20191213194943.GA959@quack2.suse.cz> References: <20191213113510.GG15474@quack2.suse.cz> <20191213153306.30744-1-tranmanphong@gmail.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Cc: "Theodore Y. Ts'o" , "Paul E. McKenney" , LKML , stable , rcu , adilger.kernel@dilger.ca, Jan Kara , linux-ext4@vger.kernel.org, linux-kernel-mentees@lists.linuxfoundation.org Subject: Re: [Linux-kernel-mentees] [PATCH V2] ext4: use rcu API in debug_print_tree X-BeenThere: linux-kernel-mentees@lists.linuxfoundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: linux-kernel-mentees-bounces@lists.linuxfoundation.org Sender: "Linux-kernel-mentees" On Fri 13-12-19 10:11:50, Joel Fernandes wrote: > On Fri, Dec 13, 2019 at 7:39 AM Phong Tran wrote: > > > > struct ext4_sb_info.system_blks was marked __rcu. > > But access the pointer without using RCU lock and dereference. > > Sparse warning with __rcu notation: > > > > block_validity.c:139:29: warning: incorrect type in argument 1 (different address spaces) > > block_validity.c:139:29: expected struct rb_root const * > > block_validity.c:139:29: got struct rb_root [noderef] * > > > > Reviewed-by: Jan Kara > > Signed-off-by: Phong Tran > > Thanks Phong! Looks like a real bug fix caught thanks to Sparse. So > let us mark for stable as well? Well, not really. The code is active only with CONFIG_EXT4_DEBUG enabled and in this case there's no race with remount (and thus sbi->system_blks changing) possible. So the change is really only to silence the sparse warning. Honza > > - Joel > > > --- > > fs/ext4/block_validity.c | 6 +++++- > > 1 file changed, 5 insertions(+), 1 deletion(-) > > > > --- > > change log: > > V2: Add Reviewed-by: Jan Kara > > > > diff --git a/fs/ext4/block_validity.c b/fs/ext4/block_validity.c > > index d4d4fdfac1a6..1ee04e76bbe0 100644 > > --- a/fs/ext4/block_validity.c > > +++ b/fs/ext4/block_validity.c > > @@ -133,10 +133,13 @@ static void debug_print_tree(struct ext4_sb_info *sbi) > > { > > struct rb_node *node; > > struct ext4_system_zone *entry; > > + struct ext4_system_blocks *system_blks; > > int first = 1; > > > > printk(KERN_INFO "System zones: "); > > - node = rb_first(&sbi->system_blks->root); > > + rcu_read_lock(); > > + system_blks = rcu_dereference(sbi->system_blks); > > + node = rb_first(&system_blks->root); > > while (node) { > > entry = rb_entry(node, struct ext4_system_zone, node); > > printk(KERN_CONT "%s%llu-%llu", first ? "" : ", ", > > @@ -144,6 +147,7 @@ static void debug_print_tree(struct ext4_sb_info *sbi) > > first = 0; > > node = rb_next(node); > > } > > + rcu_read_unlock(); > > printk(KERN_CONT "\n"); > > } > > > > -- > > 2.20.1 > > -- Jan Kara SUSE Labs, CR _______________________________________________ Linux-kernel-mentees mailing list Linux-kernel-mentees@lists.linuxfoundation.org https://lists.linuxfoundation.org/mailman/listinfo/linux-kernel-mentees