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=-10.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,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 5CF17C433DB for ; Mon, 11 Jan 2021 22:20:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2B85D22D04 for ; Mon, 11 Jan 2021 22:20:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389544AbhAKWUi (ORCPT ); Mon, 11 Jan 2021 17:20:38 -0500 Received: from mx2.suse.de ([195.135.220.15]:38894 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388713AbhAKWUh (ORCPT ); Mon, 11 Jan 2021 17:20:37 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 95610B173; Mon, 11 Jan 2021 22:19:56 +0000 (UTC) Received: by ds.suse.cz (Postfix, from userid 10065) id 9DC4CDA701; Mon, 11 Jan 2021 23:18:04 +0100 (CET) Date: Mon, 11 Jan 2021 23:18:04 +0100 From: David Sterba To: Josef Bacik Cc: linux-btrfs@vger.kernel.org, kernel-team@fb.com Subject: Re: [PATCH 06/13] btrfs: add ASSERT()'s for deleting backref cache nodes Message-ID: <20210111221804.GL6430@twin.jikos.cz> Reply-To: dsterba@suse.cz Mail-Followup-To: dsterba@suse.cz, Josef Bacik , linux-btrfs@vger.kernel.org, kernel-team@fb.com References: <3fc2e3dd35d339a7251a2ed48af3ba484769002e.1608135557.git.josef@toxicpanda.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <3fc2e3dd35d339a7251a2ed48af3ba484769002e.1608135557.git.josef@toxicpanda.com> User-Agent: Mutt/1.5.23.1-rc1 (2014-03-12) Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org Regarding the subject, you can write plain 'assert', no need to spell it exactly as it's in the code. On Wed, Dec 16, 2020 at 11:22:10AM -0500, Josef Bacik wrote: > A weird KASAN problem that Zygo reported Please add the relevant part of the report to the changelog and/or link to the report itself. > could have been easily caught > if we checked for basic things in our backref freeing code. We have two > methods of freeing a backref node > > - btrfs_backref_free_node: this just is kfree() essentially. > - btrfs_backref_drop_node: this actually unlinks the node and cleans up > everything and then calls btrfs_backref_free_node(). > > We should mostly be using btrfs_backref_drop_node(), to make sure the > node is properly unlinked from the backref cache, and only use > btrfs_backref_free_node() when we know the node isn't actually linked to > the backref cache. We made a mistake here and thus got the KASAN splat. > Make this style of issue easier to find by adding some ASSERT()'s to > btrfs_backref_free_node() and adjusting our deletion stuff to properly > init the list so we can rely on list_empty() checks working properly. > > Signed-off-by: Josef Bacik