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,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 C3CADC3F68F for ; Fri, 13 Dec 2019 23:19:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9EE7624125 for ; Fri, 13 Dec 2019 23:19:45 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=joelfernandes.org header.i=@joelfernandes.org header.b="SVp8rLnx" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726741AbfLMXTl (ORCPT ); Fri, 13 Dec 2019 18:19:41 -0500 Received: from mail-pj1-f67.google.com ([209.85.216.67]:44260 "EHLO mail-pj1-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726708AbfLMXTl (ORCPT ); Fri, 13 Dec 2019 18:19:41 -0500 Received: by mail-pj1-f67.google.com with SMTP id w5so348879pjh.11 for ; Fri, 13 Dec 2019 15:19:41 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=joelfernandes.org; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=j4OUDi2GWFJr1GQx/XFXLfcptMVLhYOJn6klY92aaOQ=; b=SVp8rLnx0teNHRRRm0PRHhUwbvbRCM2wy4jSFOelIlvzDVLv9yNq2vjqZ1mN3mlpOH k1bgyxh7/bfJ0EkseK7VPY358DRrjePvhtWMdW9sdeT2ilrvA+tm4CRWplh4/XbECcwH wsISc6Usvxqj6Ws7YK0R2/K0qpmR9IABVcmMU= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=j4OUDi2GWFJr1GQx/XFXLfcptMVLhYOJn6klY92aaOQ=; b=OiI595Wh1ZkL1zRVV6UsA9hb0Kr0iDhrDbrNELxLqAkwLYlri6VVPsCNGxI6teWonz HanYRLaT0kFDXMXpYPCKu03zZBumV0bWmOfjaJ5Tc48vHk/J5PJOSTVDyhLZH8ukji3i STxO0fuCt+/D4zb9KSUkuHIMIWJ7tmLuMHdu4fVEKaupxmDSuCuwVMbZCPnlhFtGvYWP sy5clOPXVZQuhtAhB9axutsjwJO/y+ON/959afUHoiDU0BDARGLGKfqyiaDvWbG2TuAd 5llhlcmZqiuB/Suc2pnF4qMgjegDaxH62qlgDoyDjs2KYymaLlBoi55RVe8koh5VIkCF i4Bw== X-Gm-Message-State: APjAAAUQHo3ACzMVsYsWSqJN36RIlBCdXbMm1mmtCM2rpn9RUApmkQgh Qe4fJMmJa1toYTWcovkyVn0T3g== X-Google-Smtp-Source: APXvYqwADL/M0/ouoqApRJjUcc6YwgsphiZr/cd/UqkDLYm8PsIjyhK3SpK4rAoR9Z/WqwufIc40Ig== X-Received: by 2002:a17:90a:c390:: with SMTP id h16mr2287765pjt.131.1576279180818; Fri, 13 Dec 2019 15:19:40 -0800 (PST) Received: from localhost ([2620:15c:6:12:9c46:e0da:efbf:69cc]) by smtp.gmail.com with ESMTPSA id a26sm13060069pfo.5.2019.12.13.15.19.39 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 13 Dec 2019 15:19:40 -0800 (PST) Date: Fri, 13 Dec 2019 18:19:39 -0500 From: Joel Fernandes To: Jan Kara Cc: Phong Tran , "Theodore Y. Ts'o" , adilger.kernel@dilger.ca, "Paul E. McKenney" , linux-ext4@vger.kernel.org, LKML , linux-kernel-mentees@lists.linuxfoundation.org, rcu , stable Subject: Re: [PATCH V2] ext4: use rcu API in debug_print_tree Message-ID: <20191213231939.GB195887@google.com> References: <20191213113510.GG15474@quack2.suse.cz> <20191213153306.30744-1-tranmanphong@gmail.com> <20191213194943.GA959@quack2.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191213194943.GA959@quack2.suse.cz> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-ext4-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org On Fri, Dec 13, 2019 at 08:49:43PM +0100, Jan Kara wrote: > 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. Ok, thanks for clarifying. -Joel > > 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